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19-2764; Rev 4; 7/05
KIT ATION EVALU BLE AVAILA
Low-Cost Multichemistry Battery Chargers
General Description
The MAX1908/MAX8724/MAX8765 highly integrated, multichemistry battery-charger control ICs simplify the construction of accurate and efficient chargers. These devices use analog inputs to control charge current and voltage, and can be programmed by the host or hardwired. The MAX1908/MAX8724/MAX8765 achieve high efficiency using a buck topology with synchronous rectification. The MAX1908/MAX8724/MAX8765 feature input current limiting. This feature reduces battery charge current when the input current limit is reached to avoid overloading the AC adapter when supplying the load and the battery charger simultaneously. The MAX1908/MAX8724/ MAX8765 provide outputs to monitor current drawn from the AC adapter (DC input source), battery-charging current, and the presence of an AC adapter. The MAX1908's conditioning charge feature provides 300mA to safely charge deeply discharged lithium-ion (Li+) battery packs. The MAX1908 includes a conditioning charge feature while the MAX8724/MAX8765 do not. The MAX1908/MAX8724/MAX8765 charge two to four series Li+ cells, providing more than 5A, and are available in a space-saving, 28-pin, thin QFN package (5mm x 5mm). An evaluation kit is available to speed designs.
Features
0.5% Output Voltage Accuracy Using Internal Reference (0C to +85C) 4% Accurate Input Current Limiting 5% Accurate Charge Current Analog Inputs Control Charge Current and Charge Voltage Outputs for Monitoring Current Drawn from AC Adapter Charging Current AC Adapter Presence Up to 17.6V Battery-Voltage Set Point Maximum 28V Input Voltage > 95% Efficiency Shutdown Control Input Charge Any Battery Chemistry Li+, NiCd, NiMH, Lead Acid, etc.
MAX1908/MAX8724/MAX8765
Applications
Notebook and Subnotebook Computers Personal Digital Assistants Handheld Terminals
PART MAX1908ETI MAX8724ETI MAX8765ETI
Ordering Information
TEMP RANGE -40C to +85C -40C to +85C -40C to +85C PINPACKAGE 28 Thin QFN 28 Thin QFN 28 Thin QFN PKG CODE T2855-6 T2855-6 T2855-6
Minimum Operating Circuit
AC ADAPTER INPUT 0.01 TO EXTERNAL LOAD
Pin Configuration
TOP VIEW
CELLS PGND VCTL 15 14 13 12
GND ICTL
CSSP DCIN REFIN VCTL ICTL ACIN ACOK FROM HOST P SHDN ICHG IINP CCV CCI CCS REF CLS
CSSN CELLS LDO
LDO
BST DLOV
21
DLOV
20 19
18
17
16
22 23 24 25 26 27 28 1 DCIN 2 LDO 3 CLS 4 REF 5 CCS 6 CCI 7 CCV
MAX1908 MAX8724 MAX8765
DHI LX DLO 10H PGND CSIP 0.015 CSIN BATT GND
LX
BST DHI
CSSN
BATT
CSIN
CSIP
DLO
REFIN ACOK
ACIN
MAX1908 MAX8724 MAX8765
11 10 9 8
CSSP IINP
ICHG SHDN
BATT+
THIN QFN
________________________________________________________________ Maxim Integrated Products
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Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
ABSOLUTE MAXIMUM RATINGS
DCIN, CSSP, CSSN, ACOK to GND.......................-0.3V to +30V BST to GND ............................................................-0.3V to +36V BST to LX..................................................................-0.3V to +6V DHI to LX ...................................................-0.3V to (VBST + 0.3V) LX to GND .................................................................-6V to +30V BATT, CSIP, CSIN to GND .....................................-0.3V to +20V CSIP to CSIN or CSSP to CSSN or PGND to GND ....................................................-0.3V to +0.3V CCI, CCS, CCV, DLO, ICHG, IINP, ACIN, REF to GND.......................-0.3V to (VLDO + 0.3V) DLOV, VCTL, ICTL, REFIN, CELLS, CLS, LDO, SHDN to GND .............................................-0.3V to +6V DLOV to LDO.........................................................-0.3V to +0.3V DLO to PGND .........................................-0.3V to (VDLOV + 0.3V) LDO Short-Circuit Current...................................................50mA Continuous Power Dissipation (TA = +70C) 28-Pin Thin QFN (5mm x 5mm) (derate 20.8mW/C above +70C) .........................1666.7mW Operating Temperature Range ..........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-60C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1F, LDO = DLOV, CREF = 1F; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER SYMBOL CONDITIONS VVCTL = VREFIN (2, 3, or 4 cells) VVCTL = VREFIN / 20 (2, 3, or 4 cells) VVCTL = VLDO (2, 3, or 4 cells) VCTL Default Threshold REFIN Range REFIN Undervoltage Lockout CHARGE-CURRENT REGULATION CSIP-to-CSIN Full-Scale CurrentSense Voltage VICTL = VREFIN VICTL = VREFIN VICTL = VREFIN x 0.6 Charging-Current Accuracy VICTL = VLDO MAX8765 only; VICTL = VREFIN x 0.036 MAX8724 only; VICTL = VREFIN x 0.058 Charge-Current Gain Error (MAX8765 Only) Charge-Current Offset (MAX8765 Only) ICTL Default Threshold BATT/CSIP/CSIN Input Voltage Range CSIP/CSIN Input Current VDCIN = 0 or VICTL = 0 or SHDN = 0 Charging 400 VICTL rising 71.25 -5 -5 -6 -45 -33 -2 -2 4.0 0 4.1 75 78.75 +5 +5 +6 +45 +33 +2 +2 4.2 19 1 650 % mV V V A % mV VVCTL rising (Note 1) VREFIN falling MIN -0.5 -0.5 -0.5 4.0 2.5 1.20 4.1 TYP MAX +0.5 +0.5 +0.5 4.2 3.6 1.92 V V V % UNITS
CHARGE-VOLTAGE REGULATION Battery-Regulation Voltage Accuracy
2
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Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS (continued)
(VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1F, LDO = DLOV, CREF = 1F; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Cycle-by-Cycle Maximum Current Limit ICTL Power-Down Mode Threshold Voltage (MAX1908/MAX8724 Only) ICTL, VCTL Input Bias Current REFIN Input Bias Current ICHG Transconductance (MAX1908/MAX8724 Only) ICHG Transconductance (MAX8765 Only) ICHG Transconductance Error (MAX8765 Only) ICHG Transconductance Offset (MAX8765 Only) VCSIP - VCSIN = 75mV ICHG Accuracy ICHG Output Current ICHG Output Voltage INPUT-CURRENT REGULATION CSSP-to-CSSN Full-Scale Current-Sense Voltage VCLS = VREF Input Current-Limit Accuracy Input Current-Limit Gain Error (MAX8765 Only) Input Current-Limit Offset (MAX8765 Only) CSSP, CSSN Input Voltage Range CSSP, CSSN Input Current (MAX1908/MAX8724 Only) CSSP Input Current (MAX8765 Only) VDCIN = 0 VCSSP = VCSSN = VDCIN > 8V VCSSP = VCSSN = 28V VDCIN = 0V VDCIN = 28V VCLS = VREF / 2 VCLS = 1.1V (MAX8765 only) 72 -4 -7.5 -10 -2 -2 8 0.1 350 0.1 400 75 78 +4 +7.5 +10 +2 +2 28 1 600 1 650 % mV V A A % mV VCSIP - VCSIN = 45mV VCSIP - VCSIN = 5mV VCSIP - VCSIN = 150mV, VICHG = 0 VCSIP - VCSIN = 150mV, ICHG = float GICHG GICHG SYMBOL IMAX RS2 = 0.015 CONDITIONS MIN 6.0 TYP 6.8 MAX 7.5 REFIN / 33 +1 +1 +1 +1 3 3 3.3 3.15 +5 +5 +6 +5 +40 A V % UNITS A
MAX1908/MAX8724/MAX8765
VICTL rising VVCTL = VICTL = 0 or 3V VDCIN = 0, VVCTL = VICTL = VREFIN = 5V VDCIN = 5V, VREFIN = 3V VREFIN = 5V VCSIP - VCSIN = 45mV VCSIP - VCSIN = 45mV
REFIN / REFIN / 55 100 -1 -1 -1 -1 2.7 2.85 -5 -5 -6 -5 -40 350 3.5
V
A A A/mV A/mV % A
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Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
ELECTRICAL CHARACTERISTICS (continued)
(VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1F, LDO = DLOV, CREF = 1F; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER CSSN Input Current (MAX8765 Only) CLS Input Range (MAX1908/MAX8724 Only) CLS Input Range (MAX8765 Only) CLS Input Bias Current IINP Transconductance (MAX1908/MAX8724 Only) IINP Accuracy IINP Transconductance (MAX8765 Only) IINP Transconductance Error (MAX8765 Only) IINP Transconductance Offset (MAX8765 Only) IINP Output Current IINP Output Voltage SUPPLY AND LDO REGULATOR DCIN Input Voltage Range DCIN Undervoltage-Lockout Trip Point DCIN Quiescent Current BATT Input Current LDO Output Voltage LDO Load Regulation LDO Undervoltage-Lockout Trip Point REFERENCE REF Output Voltage REF Undervoltage-Lockout Trip Point 0 < IREF < 500A VREF falling 4.072 4.096 3.1 4.120 3.9 V V IDCIN IBATT VDCIN VDCIN falling VDCIN rising 8.0V < VDCIN < 28V VBATT = 19V, VDCIN = 0 VBATT = 2V to 19V, VDCIN = 19.3V 8V < VDCIN < 28V, no load 0 < ILDO < 10mA VDCIN = 8V 3.20 5.25 200 5.4 34 4 8 7 7.4 7.5 3.2 7.85 6 1 500 5.55 100 5.15 28 V V mA A V mV V VCSSP - VCSSN = 150mV, VIINP = 0 VCSSP - VCSSN = 150mV, VIINP = float GIINP GIINP VCLS = 2V VCSSP - VCSSN = 75mV VCSSP - VCSSN = 75mV VCSSP - VCSSN = 37.5mV VCSSP - VCCSN = 75mV SYMBOL CONDITIONS VCSSP = VCSSN = 28V VDCIN = 0 VDCIN = 28V 1.6 1.1 -1 2.7 -5 -7.5 2.82 -6 -10 350 3.5 3 3 MIN TYP 0.1 0.1 MAX 1 1 REF REF +1 3.3 +5 +7.5 3.18 +6 +10 UNITS A V V A A/mV % A/mV % A A V
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Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS (continued)
(VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1F, LDO = DLOV, CREF = 1F; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER TRIP POINTS VDCIN falling, referred to VCSIN (MAX1908/MAX8724 only) BATT Power-Fail Threshold VCSSP falling, referred to VCSIN (MAX8765 only) BATT Power-Fail Threshold Hysteresis ACIN Threshold ACIN Threshold Hysteresis ACIN Input Bias Current SWITCHING REGULATOR DHI Off-Time DHI Minimum Off-Time DHI Maximum On-Time DLOV Supply Current BST Supply Current BST Input Quiescent Current LX Input Bias Current LX Input Quiescent Current DHI Maximum Duty Cycle Minimum Discontinuous-Mode Ripple Current Battery Undervoltage Charge Current Battery Undervoltage Current Threshold DHI On-Resistance High DHI On-Resistance Low DLO On-Resistance High DLO On-Resistance Low VBATT = 3V per cell (RS2 = 15m), MAX1908 only, VBATT rising CELLS = GND, MAX1908 only, VBATT rising CELLS = float, MAX1908 only, VBATT rising CELLS = VREFIN, MAX1908 only, VBATT rising VBST - VLX = 4.5V, IDHI = +100mA VBST - VLX = 4.5V, IDHI = -100mA VDLOV = 4.5V, IDLO = +100mA VDLOV = 4.5V, IDLO = -100mA 150 6.1 9.15 12.2 IDLOV IBST DLO low DHI high VDCIN = 0, VBST = 24.5V, VBATT = VLX = 20V VDCIN = 28V, VBATT = VLX = 20V VDCIN = 0, VBATT = VLX = 20V 99 VBATT = 16V, VDCIN = 19V, VCELLS = VREFIN VBATT = 16V, VDCIN = 17V, VCELLS = VREFIN 0.36 0.24 2.5 0.4 0.28 5 5 6 0.3 150 0.3 99.9 0.5 300 6.2 9.3 12.4 4 1 4 1 450 6.3 9.45 12.6 7 3.5 7 3.5 V 0.44 0.33 7.5 10 15 1 500 1 s s ms A A A A A % A mA ACIN rising (MAX8765 only) ACIN rising (MAX1908/MAX8724 only) 0.5% of REF VACIN = 2.048V -1 2.028 2.007 50 100 200 2.048 2.048 20 +1 2.068 2.089 150 mV V V mV A 50 100 150 mV SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX1908/MAX8724/MAX8765
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Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
ELECTRICAL CHARACTERISTICS (continued)
(VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = float, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1F, LDO = DLOV, CREF = 1F; CCI, CCS, and CCV are compensated per Figure 1a; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER ERROR AMPLIFIERS GMV Amplifier Transconductance GMI Amplifier Transconductance GMS Amplifier Transconductance CCI, CCS, CCV Clamp Voltage LOGIC LEVELS CELLS Input Low Voltage CELLS Input Float Voltage CELLS = float (VREFIN / 2) 0.2V VREFIN - 0.4V CELLS = 0 or VREFIN -2 0 V ACOK = 0.4V, VACIN = 3V V ACOK = 28V, VACIN = 0 0 V SHDN = 0 or VLDO VDCIN = 0, V SHDN = 5V V SHDN falling -1 -1 22 23.5 1 1 1 LDO +1 +1 25 +2 28 VREFIN /2 0.4 (VREFIN / 2) + 0.2V V V GMV GMI GMS VVCTL = VLDO, VBATT = 16.8V, CELLS = VREFIN VICTL = VREFIN, VCSIP - VCSIN = 75mV VCLS = VREF, VCSSP - VCSSN = 75mV 0.25V < VCCV,CCS,CCI < 2V 0.0625 0.5 0.5 150 0.125 1 1 300 0.2500 2.0 2.0 600 A/mV A/mV A/mV mV SYMBOL CONDITIONS MIN TYP MAX UNITS
CELLS Input High Voltage CELLS Input Bias Current ACOK AND SHDN ACOK Input Voltage Range ACOK Sink Current ACOK Leakage Current SHDN Input Voltage Range SHDN Input Bias Current SHDN Threshold SHDN Threshold Hysteresis
V A V mA A V A % of VREFIN % of VREFIN
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Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS
(VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = FLOAT, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1F, LDO = DLOV, CREF = 1F; CCI, CCS, and CCV are compensated per Figure 1a; TA = -40C to +85C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS VVCTL = VREFIN (2, 3, or 4 cells) VVCTL = VREFIN / 20 (2, 3, or 4 cells) VVCTL = VLDO (2, 3, or 4 cells) REFIN Range REFIN Undervoltage Lockout CHARGE CURRENT REGULATION CSIP-to-CSIN Full-Scale CurrentSense Voltage VICTL = VREFIN VICTL = VREFIN VICTL = VREFIN x 0.6 Charging-Current Accuracy VICTL = VLDO MAX8765 only; VICTL = VREFIN x 0.036 MAX8724 only; VICTL = VREFIN x 0.058 Charge-Current Gain Error (MAX8765 Only) Charge-Current Offset (MAX8765 Only) BATT/CSIP/CSIN Input Voltage Range CSIP/CSIN Input Current Cycle-by-Cycle Maximum Current Limit ICTL Power-Down Mode Threshold Voltage (MAX1908/MAX8724 Only) ICHG Transconductance (MAX1908/MAX8724 Only) ICHG Transconductance (MAX8765 Only) ICHG Transconductance Error (MAX8765 Only) ICHG Transconductance Offset (MAX8765 Only) GICHG GICHG IMAX VDCIN = 0 or VICTL = 0 or SHDN = 0 Charging RS2 = 0.015 6.0 REFIN / 100 2.7 2.785 -7.5 -6.5 70.5 -6 -7.5 -7.5 -50 -33 -2 -2 0 79.5 +6 +7.5 +7.5 +50 +33 +2 +2 19 1 650 7.5 REFIN / 33 3.3 3.225 +7.5 +6.5 % mV V A A % mV (Note 1) VREFIN falling MIN -0.6 -0.6 -0.6 2.5 TYP MAX +0.6 +0.6 +0.6 3.6 1.92 V V % UNITS
MAX1908/MAX8724/MAX8765
CHARGE-VOLTAGE REGULATION Battery Regulation Voltage Accuracy
VICTL rising
V
VCSIP - VCSIN = 45mV VCSIP - VCSIN = 45mV
A/mV A/mV % A
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Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
ELECTRICAL CHARACTERISTICS (continued)
(VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = FLOAT, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1F, LDO = DLOV, CREF = 1F; CCI, CCS, and CCV are compensated per Figure 1a; TA = -40C to +85C, unless otherwise noted.) (Note 2)
PARAMETER ICHG Accuracy INPUT-CURRENT REGULATION CSSP-to-CSSN Full-Scale Current-Sense Voltage VCLS = VREF Input Current-Limit Accuracy Input Current-Limit Gain Error (MAX8765 Only) Input Current-Limit Offset (MAX8765 Only) CSSP, CSSN Input Voltage Range CSSP, CSSN Input Current (MAX1908/MAX8724 Only) CSSP Input Current (MAX8765 Only) CSSN Input Current (MAX8765 Only) CLS Input Range (MAX1908/MAX8724 Only) CLS Input Range (MAX8765 Only) IINP Transconductance (MAX1908/MAX8724 Only) IINP Transconductance (MAX8765 Only) IINP Transconductance Error (MAX8765 Only) IINP Transconductance Offset (MAX8765 Only) IINP Accuracy VCSSP - VCSSN = 75mV VCSSP - VCSSN = 37.5mV GIINP GIINP VCSSP - VCSSN = 75mV VCSSP - VCCSN = 75mV VDCIN = 0 VCSSP = VCSSN = VDCIN > 8V VCSSP = VCSSN = 28V VCSSP = VCSSN = 28V VDCIN = 0V VDCIN = 28V VDCIN = 0V VDCIN = 28V 1.6 1.1 2.7 2.785 -7.5 -12 -7.5 -7.5 VCLS = VREF / 2 VCLS = 1.1V (MAX8765 only) 71.25 -5 -7.5 -10 -2 -2 8 78.75 +5 +7.5 +10 +2 +2 28 1 600 1 650 1 1 REF REF 3.3 3.225 +7.5 +12 +7.5 +7.5 % mV V A A A V V A/mV A/mV % A % % mV SYMBOL CONDITIONS VCSIP - VCSIN = 75mV VCSIP - VCSIN = 45mV VCSIP - VCSIN = 5mV MIN -7.5 -7.5 -40 TYP MAX +7.5 +7.5 +40 % UNITS
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Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS (continued)
(VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = FLOAT, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1F, LDO = DLOV, CREF = 1F; CCI, CCS, and CCV are compensated per Figure 1a; TA = -40C to +85C, unless otherwise noted.) (Note 2)
PARAMETER SUPPLY AND LDO REGULATOR DCIN Input Voltage Range DCIN Quiescent Current BATT Input Current LDO Output Voltage LDO Load Regulation REFERENCE REF Output Voltage TRIP POINTS VDCIN falling, referred to VCSIN (MAX1908/MAX8724 only) BATT Power-Fail Threshold VCSSP falling, referred to VCSIN (MAX8765 only) ACIN Threshold SWITCHING REGULATOR DHI Off-Time DHI Minimum Off-Time DHI Maximum On-Time DHI Maximum Duty Cycle Battery Undervoltage Charge Current Battery Undervoltage Current Threshold DHI On-Resistance High DHI On-Resistance Low DLO On-Resistance High DLO On-Resistance Low VBATT = 3V per cell (RS2 = 15m), MAX1908 only, VBATT rising CELLS = GND, MAX1908 only, VBATT rising CELLS = float, MAX1908 only, VBATT rising CELLS = VREFIN, MAX1908 only, VBATT rising VBST - VLX = 4.5V, IDHI = +100mA VBST - VLX = 4.5V, IDHI = -100mA VDLOV = 4.5V, IDLO = +100mA VDLOV = 4.5V, IDLO = -100mA VBATT = 16V, VDCIN = 19V, VCELLS = VREFIN VBATT = 16V, VDCIN = 17V, VCELLS = VREFIN 0.35 0.24 2.5 99 150 6.09 9.12 12.18 450 6.30 9.45 12.60 7 3.5 7 3.5 V 0.45 0.33 7.5 s s ms % mA ACIN rising (MAX8765 only) ACIN rising (MAX1908/MAX8724 only) 50 2.028 2.007 150 2.068 2.089 V 50 150 mV 0 < IREF < 500A 4.065 4.120 V VDCIN IDCIN IBATT 8V < VDCIN < 28V VBATT = 19V, VDCIN = 0 VBATT = 2V to 19V, VDCIN = 19.3V 8V < VDCIN < 28V, no load 0 < ILDO < 10mA 5.25 8 28 6 1 500 5.55 100 V mA A V mV SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX1908/MAX8724/MAX8765
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Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
ELECTRICAL CHARACTERISTICS (continued)
(VDCIN = VCSSP = VCSSN = 18V, VBATT = VCSIP = VCSIN = 12V, VREFIN = 3V, VVCTL = VICTL = 0.75 x VREFIN, CELLS = FLOAT, CLS = REF, VBST - VLX = 4.5V, ACIN = GND = PGND = 0, CLDO = 1F, LDO = DLOV, CREF = 1F; CCI, CCS, and CCV are compensated per Figure 1a; TA = -40C to +85C, unless otherwise noted.) (Note 2)
PARAMETER ERROR AMPLIFIERS GMV Amplifier Transconductance GMI Amplifier Transconductance GMS Amplifier Transconductance CCI, CCS, CCV Clamp Voltage LOGIC LEVELS CELLS Input Low Voltage CELLS Input Float Voltage CELLS = float (VREFIN / 2) 0.2V VREFIN - 0.4V 0 V A COK = 0.4V, VACIN = 3V 1 0 V SHDN falling 22 LDO 25 28 0.4 (VREFIN / 2) + 0.2V V V GMV GMI GMS VVCTL = VLDO, VBATT = 16.8V, CELLS = VREFIN VICTL = VREFIN, VCSIP - VCSIN = 75mV VCLS = VREF, VCSSP - VCSSN = 75mV 0.25V < VCCV,CCS,CCI < 2V 0.0625 0.5 0.5 150 0.250 2.0 2.0 600 A/mV A/mV A/mV mV SYMBOL CONDITIONS MIN TYP MAX UNITS
CELLS Input High Voltage ACOK AND SHDN ACOK Input Voltage Range ACOK Sink Current SHDN Input Voltage Range SHDN Threshold
V
V mA V % of VREFIN
Note 1: If both ICTL and VCTL use default mode (connected to LDO), REFIN is not used and can be connected to LDO. Note 2: Specifications to -40C are guaranteed by design and not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, VDCIN = 20V, TA = +25C, unless otherwise noted.)
LOAD-TRANSIENT RESPONSE (BATTERY INSERTION AND REMOVAL)
MAX1908 toc01
LOAD-TRANSIENT RESPONSE (STEP IN-LOAD CURRENT)
MAX1908 toc02
LOAD-TRANSIENT RESPONSE (STEP IN-LOAD CURRENT)
MAX1908 toc03
IBATT 2A/div VBATT 5V/div CCV VCCI 500mV/div VCCV 500mV/div CCI
ADAPTER CURRENT 5A/div LOAD CURRENT 5A/div VBATT 2V/div VCCI 500mV/div VCCS 500mV/div CCS CCI CCS CCI 0 0 16.8V
LOAD CURRENT 5A/div ADAPTER CURRENT 5A/div CHARGE CURRENT 2A/div VBATT 2V/div 1ms/div ICTL = LDO CHARGING CURRENT = 3A VBATT = 16.8V LOAD STEP = 0 TO 4A ISOURCE LIMIT = 5A
0
0
0
ICTL = LDO VCTL = LDO
1ms/div
1ms/div ICTL = LDO CHARGING CURRENT = 3A VBATT = 16.8V LOAD STEP = 0 TO 4A ISOURCE LIMIT = 5A
10
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Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VDCIN = 20V, TA = +25C, unless otherwise noted.)
LINE-TRANSIENT RESPONSE
MAX1908 toc04
LDO LOAD REGULATION
MAX1908 toc05
LDO LINE REGULATION
0.04 0.03 VLDO ERROR (%) 0.02 0.01 0 ILDO = 0 VLDO = 5.4V
MAX1908 toc06
0 -0.1 -0.2 VLDO ERROR (%)
0.05
VDCIN 10V/div VBATT 500mV/div
-0.3 -0.4 -0.5 -0.6 -0.7 -0.8 -0.9 -1.0 VLDO = 5.4V
-0.01 -0.02 -0.03 -0.04 -0.05
INDUCTOR CURRENT 500mA/div
ICTL = LDO VCTL = LDO ICHARGE = 3A LINE STEP 18.5V TO 27.5V 0 -0.01 -0.02 VREF ERROR (%) -0.03 -0.04 -0.05 -0.06 -0.07 -0.08 -0.09 -0.10 0 100 200
10ms/div
0
1
2
3
4
5
6
7
8
9
10
8
10 12 14 16 18 20 22 24 26 28 VIN (V)
LDO CURRENT (mA)
REF VOLTAGE LOAD REGULATION
MAX1908 toc07
REF VOLTAGE ERROR vs. TEMPERATURE
MAX1908 toc08
EFFICIENCY vs. CHARGE CURRENT
90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 VBATT = 8V VBATT = 16V VBATT = 12V
MAX1908 toc09
0.10 0.08 0.06 VREF ERROR (%) 0.04 0.02 0
100
-0.02 -0.04 -0.06 -0.08 -0.10
300
400
500
-40
-15
10
35
60
85
0.01
0.1
1
10
REF CURRENT (A)
TEMPERATURE (C)
CHARGE CURRENT (A)
FREQUENCY vs. VIN - VBATT
MAX1908 toc10
OUTPUT V/I CHARACTERISTICS
MAX1908 toc11
BATT VOLTAGE ERROR vs. VCTL
0.07 BATT VOLTAGE ERROR (%) 0.06 0.05 0.04 0.03 0.02 0.01 0 4 CELLS REFIN = 3.3V NO LOAD 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 VCTL/REFIN (%)
MAX1908 toc12
500 450 400 FREQUENCY (kHz) 350 300 250 200 150 100 50 0 0 2 4 6 ICHARGE = 3A VCTL = ICTL = LDO 4 CELLS 3 CELLS
0.5 0.4 BATT VOLTAGE ERROR (%) 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 4 CELLS 2 CELLS 3 CELLS
0.08
8 10 12 14 16 18 20 22 (VIN - VBATT) (V)
0
1
2 BATT CURRENT (A)
3
4
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11
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VDCIN = 20V, TA = +25C, unless otherwise noted.)
CURRENT-SETTING ERROR vs. ICTL
MAX1908 toc13
ICHG ERROR vs. CHARGE CURRENT
4.5 4.0 3.5 ICHG (%) 3.0 2.5 2.0 1.5 1.0 0.5 VREFIN = 3.3V VBATT = 16V VBATT = 12V VBATT = 8V
MAX1908 toc14
5 CURRENT-SETTING ERROR (%) 4 VREFIN = 3.3V 3 2 1 0 -1 0 0.5 1.0 VICTL (V) 1.5
5.0
0 2.0 0 0.5 1.0 1.5 IBATT (A) 2.0 2.5 3.0
IINP ERROR vs. SYSTEM LOAD CURRENT
30 20 IINP ERROR (%) 10 0 -10 -20 -30 -40 0 1 2 3 4 SYSTEM LOAD CURRENT (A) IINP ERROR (%) IBATT = 0
MAX1908 toc15
IINP ERROR vs. INPUT CURRENT
60 40 20 0 -20 -40 -60 -80 0 0.5 1.0 INPUT CURRENT (A) 1.5 2.0 SYSTEM LOAD = 0 ERROR DUE TO SWITCHING NOISE
MAX1908 toc16
40
80
12
______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
Pin Description
PIN 1 2 3 4 5 6 7 8 NAME DCIN LDO CLS REF CCS CCI CCV SHDN FUNCTION Charging Voltage Input. Bypass DCIN with a 1F capacitor to PGND. Device Power Supply. Output of the 5.4V linear regulator supplied from DCIN. Bypass with a 1F capacitor to GND. Source Current-Limit Input. Voltage input for setting the current limit of the input source. 4.096V Voltage Reference. Bypass REF with a 1F capacitor to GND. Input-Current Regulation Loop-Compensation Point. Connect a 0.01F capacitor to GND. Output-Current Regulation Loop-Compensation Point. Connect a 0.01F capacitor to GND. Voltage Regulation Loop-Compensation Point. Connect 1k in series with a 0.1F capacitor to GND. Shutdown Control Input. Drive SHDN logic low to shut down the MAX1908/MAX8724/MAX8765. Use with a thermistor to detect a hot battery and suspend charging. Charge-Current Monitor Output. ICHG is a scaled-down replica of the charger output current. Use ICHG to monitor the charging current and detect when the chip changes from constant-current mode to constantvoltage mode. The transconductance of (CSIP - CSIN) to ICHG is 3A/mV. AC Detect Input. Input to an uncommitted comparator. ACIN can be used to detect AC-adapter presence. AC Detect Output. High-voltage open-drain output is high impedance when VACIN is less than VREF / 2. Reference Input. Allows the ICTL and VCTL inputs to have ratiometric ranges for increased accuracy. Output Current-Limit Set Input. ICTL input voltage range is VREFIN / 32 to VREFIN. The MAX1908/MAX8724 shut down if ICTL is forced below VREFIN / 100 while the MAX8765 does not. When ICTL is equal to LDO, the set point for CSIP - CSIN is 45mV. Analog Ground Output Voltage-Limit Set Input. VCTL input voltage range is 0 to VREFIN. When VCTL is equal to LDO, the set point is (4.2 x CELLS)V. Battery Voltage Input Cell Count Input. Tri-level input for setting number of cells. GND = 2 cells, float = 3 cells, REFIN = 4 cells. Output Current-Sense Negative Input Output Current-Sense Positive Input. Connect a current-sense resistor from CSIP to CSIN. Power Ground Low-Side Power MOSFET Driver Output. Connect to low-side nMOS gate. Low-Side Driver Supply. Bypass DLOV with a 1F capacitor to GND. High-Side Power MOSFET Driver Power-Return Connection. Connect to the source of the high-side nMOS. High-Side Power MOSFET Driver Power-Supply Connection. Connect a 0.1F capacitor from LX to BST. High-Side Power MOSFET Driver Output. Connect to high-side nMOS gate. Input Current-Sense Negative Input Input Current-Sense Positive Input. Connect a current-sense resistor from CSSP to CSSN. Input-Current Monitor Output. IINP is a scaled-down replica of the input current. IINP monitors the total system current. The transconductance of (CSSP - CSSN) to IINP is 3A/mV.
MAX1908/MAX8724/MAX8765
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
ICHG ACIN ACOK REFIN ICTL GND VCTL BATT CELLS CSIN CSIP PGND DLO DLOV LX BST DHI CSSN CSSP IINP
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13
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
Detailed Description
The MAX1908/MAX8724/MAX8765 include all the functions necessary to charge Li+ batteries. A high-efficiency synchronous-rectified step-down DC-DC converter controls charging voltage and current. The device also includes input-source current limiting and analog inputs for setting the charge current and charge voltage. Control charge current and voltage using the ICTL and VCTL inputs, respectively. Both ICTL and VCTL are ratiometric with respect to REFIN, allowing compatibility with DACs or microcontrollers (Cs). Ratiometric ICTL and VCTL improve the accuracy of the charge current and voltage set point by matching VREFIN to the reference of the host. For standard applications, internal set points for ICTL and VCTL provide 3A charge current (with 0.015 sense resistor), and 4.2V (per cell) charge voltage. Connect ICTL and VCTL to LDO to select the internal set points. The MAX1908 safely conditions overdischarged cells with 300mA (with 0.015 sense resistor) until the battery-pack voltage exceeds 3.1V x number of series-connected cells. The SHDN input allows shutdown from a microcontroller or thermistor. The DC-DC converter uses external n-channel MOSFETs as the buck switch and synchronous rectifier to convert the input voltage to the required charging current and voltage. The Typical Application Circuit shown in Figure 1 uses a C to control charging current, while Figure 2 shows a typical application with charging voltage and current fixed to specific values for the application. The voltage at ICTL and the value of RS2 set the charging current. The DC-DC converter generates the control signals for the external MOSFETs to regulate the voltage and the current set by the VCTL, ICTL, and CELLS inputs. The MAX1908/MAX8724/MAX8765 feature a voltage regulation loop (CCV) and two current regulation loops (CCI and CCS). The CCV voltage regulation loop monitors BATT to ensure that its voltage does not exceed the voltage set by VCTL. The CCI battery current regulation loop monitors current delivered to BATT to ensure that it does not exceed the current limit set by ICTL. A third loop (CCS) takes control and reduces the batterycharging current when the sum of the system load and the battery-charging input current exceeds the input current limit set by CLS. external resistor mismatch error is reduced from 1% to 0.05% of the regulation voltage. Therefore, an overall voltage accuracy of better than 0.7% is maintained while using 1% resistors. The per-cell battery termination voltage is a function of the battery chemistry. Consult the battery manufacturer to determine this voltage. Connect VCTL to LDO to select the internal default setting VBATT = 4.2V x number of cells, or program the battery voltage with the following equation: V VBATT = CELLS x 4 V + 0.4 x VCTL VREFIN CELLS is the programming input for selecting cell count. Connect CELLS as shown in Table 2 to charge 2, 3, or 4 Li+ cells. When charging other cell chemistries, use CELLS to select an output voltage range for the charger. The internal error amplifier (GMV) maintains voltage regulation (Figure 3). The voltage error amplifier is compensated at CCV. The component values shown in Figures 1 and 2 provide suitable performance for most applications. Individual compensation of the voltage regulation and current regulation loops allows for optimal compensation (see the Compensation section).
Table 1. Versions Comparison
DESCRIPTION Conditioning Charge Feature ICTL Shutdown Mode ACOK Enable Condition MAX1908 Yes Yes REFIN must be ready MAX8724 No Yes REFIN must be ready MAX8765 No No Independent of REFIN
Table 2. Cell-Count Programming
CELLS GND Float VREFIN CELL COUNT 2 3 4
Setting the Battery-Regulation Voltage
The MAX1908/MAX8724/MAX8765 use a high-accuracy voltage regulator for charging voltage. The VCTL input adjusts the charger output voltage. VCTL control voltage can vary from 0 to VREFIN, providing a 10% adjustment range on the VBATT regulation voltage. By limiting the adjust range to 10% of the regulation voltage, the
14
______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765 MAX1908/MAX8724
Typical Application Circuits
AC ADAPTER INPUT 8.5V TO 28V
D1
RS1 0.01
TO EXTERNAL LOAD C1 2 x 10F
0.1F
0.1F
D2 R6 59k 1% R7 19.6k 1%
CSSP DCIN
CSSN CELLS LDO
FLOAT (3 CELLS SELECT)
C5 1F LDO
VCTL BST
C13 1F D3
R13 33
DAC OUTPUT 12.6V OUTPUT VOLTAGE VCC R8 1M
ICTL REFIN ACIN ACOK
DLOV C15 0.1F DHI LX N1b DLO C16 1F N1a
OUTPUT ADC INPUT
SHDN ICHG
ADC INPUT C14 0.1F HOST R9 20k C20 0.1F R10 10k
IINP CCV R5 1k C11 0.1F
MAX1908 MAX8724 MAX8765
PGND
L1 10H
CSIP
RS2 0.015
CSIN CCI CCS C9 0.01F AVDD/REF R19, R20, R21 10k C12 1F C10 0.01F REF CLS 7.5A INPUT CURRENT LIMIT BATT GND C4 22F BATT+
SMART BATTERY SCL SDA TEMP BATT-
SCL SDA ADC INPUT GND
PGND
GND
Figure 1. C-Controlled Typical Application Circuit
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15
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
Typical Application Circuits (continued)
AC ADAPTER INPUT 8.5V TO 28V RS1 0.01 R11 15k 0.01F 0.01F TO EXTERNAL LOAD C1 2 x 10F
P1
R12 12k
LDO
R6 59k 1%
D2 R7 19.6k 1%
CSSP ACOK DCIN
CSSN CELLS LDO
REFIN (4 CELLS SELECT)
C5 1F LDO VCTL
R14 10.5k 1% R15 8.25k 1% R16 8.25k 1%
C13 1F D3 BST DLOV C15 0.1F DHI LX
R13 33
REFIN
16.8V OUTPUT VOLTAGE 2.5A CHARGE LIMIT
ICTL ACIN
C16 1F N1a
FROM HOST P (SHUTDOWN)
N
R19 10k 1% R20 10k 1%
C12 1.5nF SHDN ICHG IINP CCV R5 1k C11 0.1F
DLO
N1b L1 10H
MAX1908 MAX8724 MAX8765
PGND
CSIP
RS2 0.015
CSIN CCI CCS C9 0.01F C10 0.01F REF CLS BATT GND C4 22F BATT+ BATTERY THM BATTC12 1F R17 19.1k 1% R18 22k 1% 4A INPUT CURRENT LIMIT
PGND GND
Figure 2. Typical Application Circuit with Fixed Charging Parameters 16 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765 MAX1908/MAX8724
Functional Diagram
MAX1908 MAX8724 MAX8765
SHDN 23.5% REFIN GND LOGIC BLOCK GND RDY 5.4V LINEAR REGULATOR 4.096V REFERENCE MAX1908/MAX8724 ONLY 1/55 ICTL SRDY
DCIN LDO
REF
REFIN
ACIN ACOK
DCIN REF/2 CCS CLS x 75mV REF GMS GM LEVEL SHIFTER GMI LEVEL SHIFTER MAX1908 ONLY BATT REFIN R1 3.1V/CELL BAT_UV LVC LVC DC-DC CONVERTER DRIVER CSI GM
N
IINP
CSSP CSSN CSIP CSIN
LEVEL SHIFTER
ICHG
BST ICTL CCI LX 75mV x REFIN DHI
CELLS
CELL SELECT LOGIC
GMV DLOV DRIVER DLO PGND
CCV VCTL 400mV x REFIN 4V
Figure 3. Functional Diagram ______________________________________________________________________________________ 17
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
Setting the Charging-Current Limit
The ICTL input sets the maximum charging current. The current is set by current-sense resistor RS2, connected between CSIP and CSIN. The full-scale differential voltage between CSIP and CSIN is 75mV; thus, for a 0.015 sense resistor, the maximum charging current is 5A. Battery-charging current is programmed with ICTL using the equation: ICHG = VICTL 0.075 x VREFIN RS2 exceeded, ensuring the battery charger does not load down the AC adapter voltage. An internal amplifier compares the voltage between CSSP and CSSN to the voltage at CLS. VCLS can be set by a resistive divider between REF and GND. Connect CLS to REF for the full-scale input current limit. The CLS voltage range for the MAX1908/MAX8724 is from 1.6V to REF, while the MAX8765 CLS voltage is from 1.1V to REF. The input current is the sum of the device current, the charger input current, and the load current. The device current is minimal (3.8mA) in comparison to the charge and load currents. Determine the actual input current required as follows: I x VBATT IINPUT = ILOAD + CHG VIN x where is the efficiency of the DC-DC converter. V CLS determines the reference voltage of the GMS error amplifier. Sense resistor RS1 and VCLS determine the maximum allowable input current. Calculate the input current limit as follows: V 0.075 IINPUT = CLS x VREF RS1 Once the input current limit is reached, the charging current is reduced until the input current is at the desired threshold. When choosing the current-sense resistor, note that the voltage drop across this resistor causes further power loss, reducing efficiency. Choose the smallest value for RS1 that achieves the accuracy requirement for the input current-limit set point.
The input voltage range for ICTL is V REFIN / 32 to VREFIN. The MAX1908/MAX8724 shut down if ICTL is forced below VREFIN / 100 (min), while the MAX8765 does not. Connect ICTL to LDO to select the internal default fullscale, charge-current sense voltage of 45mV. The charge current when ICTL = LDO is: ICHG = 0.045V RS2
where RS2 is 0.015, providing a charge-current set point of 3A. The current at the ICHG output is a scaled-down replica of the battery output current being sensed across CSIP and CSIN (see the Current Measurement section). When choosing the current-sense resistor, note that the voltage drop across this resistor causes further power loss, reducing efficiency. However, adjusting ICTL to reduce the voltage across the current-sense resistor can degrade accuracy due to the smaller signal to the input of the current-sense amplifier. The chargingcurrent-error amplifier (GMI) is compensated at CCI (see the Compensation section).
Conditioning Charge
The MAX1908 includes a battery-voltage comparator that allows a conditioning charge of overdischarged Li+ battery packs. If the battery-pack voltage is less than 3.1V x number of cells programmed by CELLS, the MAX1908 charges the battery with 300mA current when using sense resistor RS2 = 0.015. After the battery voltage exceeds the conditioning charge threshold, the MAX1908 resumes full-charge mode, charging to the programmed voltage and current limits. The MAX8724/MAX8765 do not offer this feature.
Setting the Input Current Limit
The total input current (from an AC adapter or other DC source) is a function of the system supply current and the battery-charging current. The input current regulator limits the input current by reducing the charging current when the input current exceeds the input current-limit set point. System current normally fluctuates as portions of the system are powered up or down. Without input current regulation, the source must be able to supply the maximum system current and the maximum charger input current simultaneously. By using the input current limiter, the current capability of the AC adapter can be lowered, reducing system cost. The MAX1908/MAX8724/MAX8765 limit the battery charge current when the input current-limit threshold is
18
AC Adapter Detection
Connect the AC adapter voltage through a resistive divider to ACIN to detect when AC power is available, as shown in Figure 1. ACIN voltage rising trip point is VREF / 2 with 20mV hysteresis. ACOK is an open-drain output and is high impedance when ACIN is less than VREF / 2. Since ACOK can withstand 30V (max), ACOK
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Low-Cost Multichemistry Battery Chargers
can drive a p-channel MOSFET directly at the charger input, providing a lower dropout voltage than a Schottky diode (Figure 2). In the MAX1908/MAX8724 the ACOK comparator is enabled after REFIN is ready. In the MAX8765, the ACOK comparator is independent of REFIN. CCV, CCI, CCS, and LVC Control Blocks The MAX1908/MAX8724/MAX8765 control input current (CCS control loop), charge current (CCI control loop), or charge voltage (CCV control loop), depending on the operating condition. The three control loops, CCV, CCI, and CCS are brought together internally at the LVC amplifier (lowest voltage clamp). The output of the LVC amplifier is the feedback control signal for the DC-DC controller. The output of the GM amplifier that is the lowest sets the output of the LVC amplifier and also clamps the other two control loops to within 0.3V above the control point. Clamping the other two control loops close to the lowest control loop ensures fast transition with minimal overshoot when switching between different control loops. DC-DC Controller The MAX1908/MAX8724/MAX8765 feature a variable offtime, cycle-by-cycle current-mode control scheme. Depending upon the conditions, the MAX1908/MAX8724/ MAX8765 work in continuous or discontinuous-conduction mode.
MAX1908/MAX8724/MAX8765 MAX1908/MAX8724
Current Measurement
Use ICHG to monitor the battery-charging current being sensed across CSIP and CSIN. The ICHG voltage is proportional to the output current by the equation: VICHG = ICHG x RS2 x GICHG x R9 where ICHG is the battery-charging current, GICHG is the transconductance of ICHG (3A/mV typ), and R9 is the resistor connected between ICHG and ground. Leave ICHG unconnected if not used. Use IINP to monitor the system input current being sensed across CSSP and CSSN. The voltage of IINP is proportional to the input current by the equation: VIINP = IINPUT x RS1 x GIINP x R10 where IINPUT is the DC current being supplied by the AC adapter power, GIINP is the transconductance of IINP (3A/mV typ), and R10 is the resistor connected between IINP and ground. ICHG and IINP have a 0 to 3.5V output voltage range. Leave IINP unconnected if not used.
Continuous-Conduction Mode
With sufficient charger loading, the MAX1908/MAX8724/ MAX8765 operate in continuous-conduction mode (inductor current never reaches zero) switching at 400kHz if the BATT voltage is within the following range: 3.1V x (number of cells) < VBATT < (0.88 x VDCIN ) The operation of the DC-DC controller is controlled by the following four comparators as shown in Figure 4: * IMIN--Compares the control point (LVC) against 0.15V (typ). If IMIN output is low, then a new cycle cannot begin. * CCMP--Compares the control point (LVC) against the charging current (CSI). The high-side MOSFET ontime is terminated if the CCMP output is high. * IMAX--Compares the charging current (CSI) to 6A (RS2 = 0.015). The high-side MOSFET on-time is terminated if the IMAX output is high and a new cycle cannot begin until IMAX goes low. * ZCMP--Compares the charging current (CSI) to 333mA (RS2 = 0.015). If ZCMP output is high, then both MOSFETs are turned off.
LDO Regulator
LDO provides a 5.4V supply derived from DCIN and can deliver up to 10mA of load current. The MOSFET drivers are powered by DLOV and BST, which must be connected to LDO as shown in Figure 1. LDO supplies the 4.096V reference (REF) and most of the control circuitry. Bypass LDO with a 1F capacitor to GND.
Shutdown
The MAX1908/MAX8724/MAX8765 feature a low-power shutdown mode. Driving SHDN low shuts down the MAX1908/MAX8724/MAX8765. In shutdown, the DCDC converter is disabled and CCI, CCS, and CCV are pulled to ground. The IINP and ACOK outputs continue to function. SHDN can be driven by a thermistor to allow automatic shutdown of the MAX1908/MAX8724/MAX8765 when the battery pack is hot. The shutdown falling threshold is 23.5% (typ) of VREFIN with 1% VREFIN hysteresis to provide smooth shutdown when driven by a thermistor.
DC-DC Converter
The MAX1908/MAX8724/MAX8765 employ a buck regulator with a bootstrapped nMOS high-side switch and a low-side nMOS synchronous rectifier.
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19
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
DC-DC Functional Diagram
5ms S BST IMAX 1.8V R Q CSSP AC ADAPTER RS1 CSSN BST DHI DHI LX CHG N1a CBST D3 LDO
RESET
MAX1908 MAX8724 MAX8765
R Q
CSS X20
CCMP
IMIN 0.15V
S
Q DLO tOFF GENERATOR DLO N1b L1
ZCMP 0.1V CSI X20 LVC GMS
CSIP RS2 CSIN BATT COUT GMI BATTERY
GMV SETV CONTROL SETI CLS CELLS CELL SELECT LOGIC
CCS
CCI
CCV
Figure 4. DC-DC Functional Diagram 20 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
In normal operation, the controller starts a new cycle by turning on the high-side n-channel MOSFET and turning off the low-side n-channel MOSFET. When the charge current is greater than the control point (LVC), CCMP goes high and the off-time is started. The off-time turns off the high-side n-channel MOSFET and turns on the low-side n-channel MOSFET. The operational frequency is governed by the off-time and is dependent upon VDCIN and VBATT. The off-time is set by the following equations: V - VBATT t OFF = 2.5s x DCIN VDCIN t ON = where: V xt IRIPPLE = BATT OFF L f= 1 t ON + t OFF L x IRIPPLE VCSSN - VBATT
Discontinuous Conduction
The MAX1908/MAX8724/MAX8765 enter discontinuousconduction mode when the output of the LVC control point falls below 0.15V. For RS2 = 0.015, this corresponds to 0.5A: IMIN = 0.15V = 0.5A 20 x RS2
MAX1908/MAX8724/MAX8765 MAX1908/MAX8724
for RS2 = 0.015. In discontinuous mode, a new cycle is not started until the LVC voltage rises above 0.15V. Discontinuousmode operation can occur during conditioning charge of overdischarged battery packs, when the charge current has been reduced sufficiently by the CCS control loop, or when the battery pack is near full charge (constant-voltage-charging mode). MOSFET Drivers The low-side driver output DLO switches between PGND and DLOV. DLOV is usually connected through a filter to LDO. The high-side driver output DHI is bootstrapped off LX and switches between VLX and VBST. When the low-side driver turns on, BST rises to one diode voltage below DLOV. Filter DLOV with a lowpass filter whose cutoff frequency is approximately 5kHz (Figure 1): fC = 1 1 = = 4.8kHz 2RC 2 x 33 x 1F
These equations result in fixed-frequency operation over the most common operating conditions. At the end of the fixed off-time, another cycle begins if the control point (LVC) is greater than 0.15V, IMIN = high, and the peak charge current is less than 6A (RS2 = 0.015), IMAX = high. If the charge current exceeds IMAX, the on-time is terminated by the IMAX comparator. IMAX governs the maximum cycle-by-cycle current limit and is internally set to 6A (RS2 = 0.015). IMAX protects against sudden overcurrent faults. If, during the off-time, the inductor current goes to zero, ZCMP = high, both the high- and low-side MOSFETs are turned off until another cycle is ready to begin. There is a minimum 0.3s off-time when the (VDCIN VBATT) differential becomes too small. If VBATT 0.88 x V DCIN , then the threshold for minimum off-time is reached and the tOFF is fixed at 0.3s. A maximum ontime of 5ms allows the controller to achieve > 99% duty cycle in continuous-conduction mode. The switching frequency in this mode varies according to the equation: 1 f= L x IRIPPLE + 0.3s (VCSSN - VBATT )
Dropout Operation The MAX1908/MAX8724/MAX8765 have 99% duty-cycle capability with a 5ms (max) on-time and 0.3s (min) offtime. This allows the charger to achieve dropout performance limited only by resistive losses in the DC-DC converter components (D1, N1, RS1, and RS2, Figure 1). Replacing diode D1 with a p-channel MOSFET driven by ACOK improves dropout performance (Figure 2). The dropout voltage is set by the difference between DCIN and CSIN. When the dropout voltage falls below 100mV, the charger is disabled; 200mV hysteresis ensures that the charger does not turn back on until the dropout voltage rises to 300mV. Compensation Each of the three regulation loops--input current limit, charging current limit, and charging voltage limit--are compensated separately using CCS, CCI, and CCV, respectively.
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21
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
where RL varies with load according to RL = VBATT / ICHG. Output zero due to output capacitor ESR:
BATT GMOUT
fZ _ ESR =
1 2RESR x COUT
RESR CCV GMV COUT
RL
The loop transfer function is given by: LTF = GMOUT x RL x GMV x ROGMV x
RCV CCV
ROGMV
(1+ sCOUT x RESR )(1+ sCCV x RCV ) (1+ sCCV x ROGMV )(1+ sCOUT x RL )
REF
Assuming the compensation pole is a very low frequency, and the output zero is a much higher frequency, the crossover frequency is given by: fCO _ CV = GMV x RCV x GMOUT 2COUT
Figure 5. CCV Loop Diagram
CCV Loop Definitions
Compensation of the CCV loop depends on the parameters and components shown in Figure 5. CCV and RCV are the CCV loop compensation capacitor and series resistor. RESR is the equivalent series resistance (ESR) of the charger output capacitor (COUT). RL is the equivalent charger output load, where R L = VBATT / ICHG. The equivalent output impedance of the GMV amplifier, R OGMV 10M. The voltage amplifier transconductance, GMV = 0.125A/mV. The DC-DC converter transconductance, GMOUT = 3.33A/V: GMOUT = 1 ACSI x RS2
To calculate RCV and CCV values of the circuit of Figure 2: Cells = 4 COUT = 22F VBATT = 16.8V ICHG = 2.5A GMV = 0.125A/mV GMOUT = 3.33A/V ROGMV = 10M f = 400kHz Choose crossover frequency to be 1/5th the MAX1908's 400kHz switching frequency: fCO _ CV = GMV x RCV x GMOUT = 80kHz 2COUT
where A CSI = 20, and RS2 is the charging currentsense resistor in the Typical Application Circuits. The compensation pole is given by: fP _ CV = 1 2ROGMV x CCV
Solving yields RCV = 26k. Conservatively set RCV = 1k, which sets the crossover frequency at: fCO_CV = 3kHz Choose the output-capacitor ESR so the output-capacitor zero is 10 times the crossover frequency: RESR = 1 2 x 10 x fCO _ CV x COUT = 0.24
The compensation zero is given by: fZ _ CV = 1 2RCV x CCV
The output pole is given by: fP _ OUT = 1 2RL x COUT fZ _ ESR =
1 = 2.412MHz 2RESR x COUT
22
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Low-Cost Multichemistry Battery Chargers
The 22F ceramic capacitor has a typical ESR of 0.003, which sets the output zero at 2.412MHz. The output pole is set at: fP _ OUT = where: RL = VBATT = Battery ESR ICHG 1 = 1.08kHz 2RL x COUT
CCI Loop Definitions
Compensation of the CCI loop depends on the parameters and components shown in Figure 7. CCI is the CCI loop compensation capacitor. ACSI is the internal gain of the current-sense amplifier. RS2 is the charge current-sense resistor, RS2 = 15m. ROGMI is the equivalent output impedance of the GMI amplifier 10M. GMI is the charge-current amplifier transconductance = 1A/mV. GMOUT is the DC-DC converter transconductance = 3.3A/V. The CCI loop is a single-pole system with a dominant pole compensation set by fP_CI: fP _ CI = 1 2ROGMI x CCI
MAX1908/MAX8724/MAX8765 MAX1908/MAX8724
Set the compensation zero (fZ_CV) so it is equivalent to the output pole (fP_OUT = 1.08kHz), effectively producing a pole-zero cancellation and maintaining a singlepole system response: fZ _ CV = 1 2RCV x CCV
The loop transfer function is given by: LTF = GMOUT x A CSI x RS2 x GMI Since: ROGMI 1+ sROGMI x CCI
1 CCV = = 147nF 2RCV x 1.08kHz Choose CCV = 100nF, which sets the compensation zero (fZ_CV) at 1.6kHz. This sets the compensation pole: fP _ CV = 1 2ROGMV x CCV = 0.16Hz
GMOUT =
1 ACSI x RS2
The loop transfer function simplifies to: LTF = GMI x ROGMI 1+ sROGMI x CCI
CCV LOOP GAIN vs. FREQUENCY
80 60 PHASE (DEGREES) 40 GAIN (dB) 20 0 -20 -40 -60 1 10 100 1k 10k 100k 1M FREQUENCY (Hz) -45 -60 -75 -90 -105 -120 -135 1 10
CCV LOOP PHASE vs. FREQUENCY
100
1k
10k
100k
1M
FREQUENCY (Hz)
Figure 6. CCV Loop Gain/Phase vs. Frequency ______________________________________________________________________________________ 23
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
To calculate the CCI loop compensation pole, CCI: GMI = 1A/mV GMOUT = 3.33A/V ROGMI = 10M f = 400kHz Choose crossover frequency f CO_CI to be 1/5th the MAX1908/MAX8724/MAX8765 switching frequency: fCO _ CI = GMI = 80kHz 2CCI
CSIP GMOUT RS2
CSIN
CSI
CCI GMI
CCI
ROGMI
ICTL
Solving for CCI, CCI = 2nF. To be conservative, set CCI = 10nF, which sets the crossover frequency at: fCO _ CI = GMI = 16kHz 210nF
Figure 7. CCI Loop Diagram
The crossover frequency is given by: fCO _ CI = GMI 2CCI
The compensation pole, fP_CI is set at: fP _ CI = GMI = 0.0016Hz 2ROGMI x CCI
The CCI loop dominant compensation pole: fP _ CI = 1 2ROGMI x CCI
CCS Loop Definitions
Compensation of the CCS loop depends on the parameters and components shown in Figure 9. CCS is the CCS loop compensation capacitor. ACSS is the internal gain of the current-sense amplifier. RS1 is the input currentsense resistor, RS1 = 10m. ROGMS is the equivalent output impedance of the GMS amplifier 10M. GMS is
CCI LOOP PHASE vs. FREQUENCY
0 -15 PHASE (DEGREES) -30 -45 -60 -75 -90 -105
where the GMI amplifier output impedance, ROGMI = 10M.
CCI LOOP GAIN vs. FREQUENCY
100 80 60 GAIN (dB) 40 20 0 -20 -40 -60 0.1 1 10 100 1k 10k 100k 1M FREQUENCY (Hz)
0.1
1
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
Figure 8. CCI Loop Gain/Phase vs. Frequency 24 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
the charge-current amplifier transconductance = 1A/mV. GM IN is the DC-DC converter transconductance = 3.3A/V. The CCS loop is a single-pole system with a dominant pole compensation set by fP_CS: fP _ CS = 1 2ROGMS x CCS
MAX1908/MAX8724/MAX8765 MAX1908/MAX8724
CSSP GMIN RS1
CSSN
CSS
The loop transfer function is given by: LTF = GMIN x A CSS x RS1x GMS x Since: 1 GMIN = ACSS x RS1 Then, the loop transfer function simplifies to: LTF = GMS x ROGMS 1+ sROGMS x CCS
Figure 9. CCS Loop Diagram
ROGMS 1 + sROGMS x CCS
CCS GMS
CCS
ROGMS
CLS
The CCS loop dominant compensation pole: fP _ CS = 1 2ROGMS x CCS
The crossover frequency is given by: fCO _ CS = GMS 2CCS
where the GMS amplifier output impedance, ROGMS = 10M. To calculate the CCI loop compensation pole, CCS: GMS = 1A/mV GMIN = 3.33A/V ROGMS = 10M f = 400kHz
CCS LOOP GAIN vs. FREQUENCY
100 80 60 GAIN (dB) 40 20 0 -20 -40 -60 0.1 1 10 100 1k 10k 100k 1M FREQUENCY (Hz) PHASE (DEGREES) 0 -15 -30 -45 -60 -75 -90 -105 0.1 1
CCS LOOP PHASE vs. FREQUENCY
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
Figure 10. CCS Loop Gain/Phase vs. Frequency ______________________________________________________________________________________ 25
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
Choose crossover frequency fCO_CS to be 1/5th the MAX1908/MAX8724/MAX8765 switching frequency: fCO _ CS = GMS = 80kHz 2CCS where: tOFF = 2.5s x (VDCIN - VBATT) / VDCIN VBATT < 0.88 x VDCIN or: tOFF = 0.3s Solving for CCS, CCS = 2nF. To be conservative, set CCS = 10nF, which sets the crossover frequency at: fCO _ CS = GMS = 16kHz 210nF VBATT > 0.88 x VDCIN Figure 11 illustrates the variation of ripple current vs. battery voltage when charging at 3A with a fixed 19V input voltage. Higher inductor values decrease the ripple current. Smaller inductor values require higher saturation current capabilities and degrade efficiency. Designs for ripple current, IRIPPLE = 0.3 x ICHG usually result in a good balance between inductor size and efficiency.
The compensation pole, fP_CS is set at: fP _ CS = 1 = 0.0016Hz 2ROGMS x CCS
Input Capacitor
Input capacitor C1 must be able to handle the input ripple current. At high charging currents, the DC-DC converter operates in continuous conduction. In this case, the ripple current of the input capacitor can be approximated by the following equation: IC1 = ICHG D - D2 where: IC1 = input capacitor ripple current. D = DC-DC converter duty ratio. ICHG = battery-charging current. Input capacitor C1 must be sized to handle the maximum ripple current that occurs during continuous conduction. The maximum input ripple current occurs at 50% duty cycle; thus, the worst-case input ripple current is 0.5 x ICHG. If the input-to-output voltage ratio is such that the DC-DC converter does not operate at a 50% duty cycle, then the worst-case capacitor current occurs where the duty cycle is nearest 50%. The input capacitor ESR times the input ripple current sets the ripple voltage at the input, and should not exceed 0.5V ripple. Choose the ESR of C1 according to: ESRC1 < 0.5V IC1
Component Selection
Table 3 lists the recommended components and refers to the circuit of Figure 2. The following sections describe how to select these components.
Inductor Selection
Inductor L1 provides power to the battery while it is being charged. It must have a saturation current of at least the charge current (ICHG), plus 1/2 the current ripple IRIPPLE: ISAT = ICHG + (1/2) IRIPPLE Ripple current varies according to the equation: IRIPPLE = (VBATT) x tOFF / L
RIPPLE CURRENT vs. BATTERY VOLTAGE
1.5 3 CELLS RIPPLE CURRENT (A) 4 CELLS
1.0
0.5 VDCIN = 19V VCTL = ICTL = LDO 0 8 9 10 11 12 13 14 15 16 17 18 VBATT (V)
The input capacitor size should allow minimal output voltage sag at the highest switching frequency: IC1 dV = C1 dt 2
Figure 11. Ripple Current vs. Battery Voltage 26
______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
where dV is the maximum voltage sag of 0.5V while delivering energy to the inductor during the high-side MOSFET on-time, and dt is the period at highest operating frequency (400kHz): I 2.5s C1 > C1 x 2 0.5V Both tantalum and ceramic capacitors are suitable in most applications. For equivalent size and voltage rating, tantalum capacitors have higher capacitance, but also higher ESR than ceramic capacitors. This makes it more critical to consider ripple current and power-dissipation ratings when using tantalum capacitors. A single ceramic capacitor often can replace two tantalum capacitors in parallel. the MOSFET. Choose N1b with either an internal Schottky diode or body diode capable of carrying the maximum charging current during the dead time. The Schottky diode D3 provides the supply current to the high-side MOSFET driver.
MAX1908/MAX8724/MAX8765 MAX1908/MAX8724
Layout and Bypassing
Bypass DCIN with a 1F capacitor to power ground (Figure 1). D2 protects the MAX1908/MAX8724/ MAX8765 when the DC power source input is reversed. A signal diode for D2 is adequate because DCIN only powers the internal circuitry. Bypass LDO, REF, CCV, CCI, CCS, ICHG, and IINP to analog ground. Bypass DLOV to power ground. Good PC board layout is required to achieve specified noise, efficiency, and stable performance. The PC board layout artist must be given explicit instructions-- preferably, a pencil sketch showing the placement of the power-switching components and high-current routing. Refer to the PC board layout in the MAX1908 evaluation kit for examples. Separate analog and power grounds are essential for optimum performance. Use the following step-by-step guide: 1) Place the high-power connections first, with their grounds adjacent: a) Minimize the current-sense resistor trace lengths, and ensure accurate current sensing with Kelvin connections. b) Minimize ground trace lengths in the high-current paths. c) Minimize other trace lengths in the high-current paths. d) Use > 5mm wide traces. e) Connect C1 to high-side MOSFET (10mm max length). f) LX node (MOSFETs, inductor (15mm max length)). Ideally, surface-mount power components are flush against one another with their ground terminals almost touching. These high-current grounds are then connected to each other with a wide, filled zone of top-layer copper, so they do not go through vias. The resulting top-layer power ground plane is connected to the normal ground plane at the MAX1908/MAX8724/MAX8765s' backside exposed pad. Other high-current paths should also be minimized, but focusing primarily on short ground and current-sense connections eliminates most PC board layout problems.
27
Output Capacitor
The output capacitor absorbs the inductor ripple current. The output capacitor impedance must be significantly less than that of the battery to ensure that it absorbs the ripple current. Both the capacitance and ESR rating of the capacitor are important for its effectiveness as a filter and to ensure stability of the DC-DC converter (see the Compensation section). Either tantalum or ceramic capacitors can be used for the output filter capacitor.
MOSFETs and Diodes
Schottky diode D1 provides power to the load when the AC adapter is inserted. This diode must be able to deliver the maximum current as set by RS1. For reduced power dissipation and improved dropout performance, replace D1 with a p-channel MOSFET (P1) as shown in Figure 2. Take caution not to exceed the maximum VGS of P1. Choose resistors R11 and R12 to limit the VGS. The n-channel MOSFETs (N1a, N1b) are the switching devices for the buck controller. High-side switch N1a should have a current rating of at least the maximum charge current plus one-half the ripple current and have an on-resistance (RDS(ON)) that meets the power dissipation requirements of the MOSFET. The driver for N1a is powered by BST. The gate-drive requirement for N1a should be less than 10mA. Select a MOSFET with a low total gate charge (Q GATE ) and determine the required drive current by IGATE = QGATE x f (where f is the DC-DC converter's maximum switching frequency). The low-side switch (N1b) has the same current rating and power dissipation requirements as N1a, and should have a total gate charge less than 10nC. N2 is used to provide the starting charge to the BST capacitor (C15). During the dead time (50ns, typ) between N1a and N1b, the current is carried by the body diode of
______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers MAX1908/MAX8724/MAX8765
2) Place the IC and signal components. Keep the main switching node (LX node) away from sensitive analog components (current-sense traces and REF capacitor). Important: The IC must be no further than 10mm from the current-sense resistors. Keep the gate-drive traces (DHI, DLO, and BST) shorter than 20mm, and route them away from the current-sense lines and REF. Place ceramic bypass capacitors close to the IC. The bulk capacitors can be placed further away. 3) Use a single-point star ground placed directly below the part at the backside exposed pad of the MAX1908/MAX8724/MAX8765. Connect the power ground and normal ground to this node.
Table 3. Component List for Circuit of Figure 2
DESIGNATION QTY C1 2 DESCRIPTION 10F, 50V 2220-size ceramic capacitors TDK C5750X7R1H106M 22F, 25V 2220-size ceramic capacitor TDK C5750X7R1E226M 1F, 25V X7R ceramic capacitor (1206) Murata GRM31MR71E105K Taiyo Yuden TMK316BJ105KL TDK C3216X7R1E105K 0.01F, 16V ceramic capacitors (0402) Murata GRP155R71E103K Taiyo Yuden EMK105BJ103KV TDK C1005X7R1E103K 0.1F, 25V X7R ceramic capacitors (0603) Murata GRM188R71E104K TDK C1608X7R1E104K 1F, 6.3V X5R ceramic capacitors (0603) Murata GRM188R60J105K Taiyo Yuden JMK107BJ105KA TDK C1608X5R1A105K 10A Schottky diode (D-PAK) Diodes, Inc. MBRD1035CTL ON Semiconductor MBRD1035CTL RS2 D2 1 Schottky diode Central Semiconductor CMPSH1-4 U1 1 1 DESIGNATION QTY D3 1 DESCRIPTION Schottky diode Central Semiconductor CMPSH1-4 10H, 4.4A inductor Sumida CDRH104R-100NC TOKO 919AS-100M Dual, n-channel, 8-pin SO MOSFET Fairchild FDS6990A or FDS6990S Single, p-channel, 8-pin SO MOSFET Fairchild FDS6675 1k 5% resistor (0603) 59k 1% resistor (0603) 19.6k 1% resistor (0603) 12k 5% resistor (0603) 15k 5% resistor (0603) 33 5% resistor (0603) 10.5k 1% resistor (0603) 8.25k 1% resistors (0603) 19.1k 1% resistor (0603) 22k 1% resistor (0603) 10k 1% resistors (0603) 0.01 1%, 0.5W 2010 sense resistor Vishay Dale WSL2010 0.010 1.0% IRC LRC-LR2010-01-R010-F 0.015 1%, 0.5W 2010 sense resistor Vishay Dale WSL2010 0.015 1.0% IRC LRC-LR2010-01-R015-F MAX1908ETI, MAX8724ETI, or MAX8765ETI
L1
1
C4
1
N1 P1 R5 R6 R7 R11 R12 R13 R14 R15, R16 R17 R18 R19, R20 RS1
1 1 1 1 1 1 1 1 1 2 1 1 2 1
C5
1
C9, C10
2
C11, C14, C15, C20
4
C12, C13, C16
3
D1 (optional)
1
Chip Information
TRANSISTOR COUNT: 3772 PROCESS: BiCMOS
28 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
QFN THIN.EPS
MAX1908/MAX8724/MAX8765 MAX1908/MAX8724
D2 D D/2 MARKING k
C L
b D2/2 L
0.10 M C A B
AAAAA
E/2 E2/2 E (NE-1) X e
C L
E2
PIN # 1 I.D.
DETAIL A
e (ND-1) X e
e/2
PIN # 1 I.D. 0.35x45 DETAIL B
e
L1
L
C L
C L
L e 0.10 C A 0.08 C e
L
C
A1 A3
PACKAGE OUTLINE, 16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm
-DRAWING NOT TO SCALE-
21-0140
I
1
2
COMMON DIMENSIONS
PKG. 16L 5x5 20L 5x5 28L 5x5 32L 5x5 40L 5x5 SYMBOL MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX.
EXPOSED PAD VARIATIONS PKG. CODES
D2
MIN. NOM. MAX.
E2
MIN. NOM. MAX.
exceptions
L
A A1 A3 b D E e k L
0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0 0.02 0.05 0 0.02 0.05 0 0.02 0.05 0 0.02 0.05 0 0.02 0.05 0.20 REF. 0.20 REF. 0.20 REF. 0.20 REF. 0.20 REF. 0.25 0.30 0.35 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 0.15 0.20 0.25 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 0.65 BSC. 0.50 BSC. 0.80 BSC. 0.50 BSC. 0.40 BSC.
0.15
DOWN BONDS ALLOWED
- 0.25 - 0.25 - 0.25 0.35 0.45 0.25 - 0.25 0.30 0.40 0.50 0.45 0.55 0.65 0.45 0.55 0.65 0.30 0.40 0.50 0.40 0.50 0.60 L1 0.30 0.40 0.50 16 20 28 32 N 40 ND 10 4 5 7 8 10 4 5 7 8 NE WHHC WHHD-1 WHHD-2 ----WHHB JEDEC
NOTES: 1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. 2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. 3. N IS THE TOTAL NUMBER OF TERMINALS. 4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE. 5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm FROM TERMINAL TIP.
T1655-2 3.00 T1655-3 3.00 T1655N-1 3.00 T2055-3 3.00 3.00 T2055-4 T2055-5 3.15 T2855-3 3.15 T2855-4 2.60 T2855-5 2.60 3.15 T2855-6 T2855-7 2.60 T2855-8 3.15 T2855N-1 3.15 T3255-3 3.00 T3255-4 3.00 T3255-5 3.00 T3255N-1 3.00 T4055-1 3.20
3.10 3.10 3.10 3.10 3.10 3.25 3.25 2.70 2.70 3.25 2.70 3.25 3.25 3.10 3.10 3.10 3.10 3.30
3.20 3.20 3.20 3.20 3.20 3.35 3.35 2.80 2.80 3.35 2.80 3.35 3.35 3.20 3.20 3.20 3.20 3.40
3.00 3.00 3.00 3.00 3.00 3.15 3.15 2.60 2.60 3.15 2.60 3.15 3.15 3 3.00 3 3.00 3.00 3.00 3.20
3.10 3.10 3.10 3.10 3.10 3.25 3.25 2.70 2.70 3.25 2.70 3.25 3.25 3.10 3.10 3.10 3.10 3.30
3.20 3.20 3.20 3.20 3.20 3.35 3.35 2.80 2.80 3.35 2.80 3.35 3.35 .20 .20 3.20 3.20 3.40
** ** ** ** ** 0.40 ** ** ** ** ** 0.40 ** ** ** ** ** **
YES NO NO YES NO YES YES YES NO NO YES YES NO YES NO YES NO YES
** SEE COMMON DIMENSIONS TABLE
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY. 7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION. 8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS. 9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT EXPOSED PAD DIMENSION FOR T2855-3 AND T2855-6. 10. WARPAGE SHALL NOT EXCEED 0.10 mm. 11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY. 12. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY. 13. LEAD CENTERLINES TO BE AT TRUE POSITION AS DEFINED BY BASIC DIMENSION "e", 0.05.
PACKAGE OUTLINE, 16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm
-DRAWING NOT TO SCALE-
21-0140
I
2
2
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 29 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

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