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19-3169; Rev 0; 1/04
Power-Source Selector for Dual-Battery Systems
General Description
The MAX1538 selector provides power-source control for dual-battery systems. The device selects between an AC adapter and dual batteries based on the presence of the three power sources and the state of charge of each battery. The MAX1538 includes analog comparators to detect AC/airline-adapter presence and determine battery undervoltage. Fast analog circuitry allows the device to switch between power sources to implement a break-before-make time, which allows hot swapping of battery packs. The MAX1538 independently performs power-source monitoring and selection, freeing the system power-management P for other tasks. This simplifies the development of P power-management firmware and allows the P to enter standby, reducing system power consumption. The MAX1538 supports "relearn mode," which allows the system to measure and fully utilize battery capacity. In this state, the part allows the selected battery to be discharged even when an AC adapter is present. The MAX1538 can also be used to power the system in an aircraft. On detecting an airline adapter, the MAX1538 automatically disables charging or discharging of battery packs and only allows the system to be powered from the adapter. The MAX1538 is available in a space-saving 28-pin thin QFN package with a maximum footprint of 5mm x 5mm.
SYSTEM LOAD
Features
Automatically Detects and Responds to Low-Battery Voltage Condition Battery Insertion and Removal AC-Adapter Presence Airline-Adapter Presence Step-Down and Step-Up Charger Compatibility Fast Break-Before-Make Selection Allows Hot Swapping of Power Sources No External Schottky Diodes Needed 50A Maximum Battery Quiescent Current Implements Battery Capacity Relearning Allows Usage of Aircraft Supply Direct Drive of P-Channel MOSFETs Simplifies Power-Management P Firmware 4.75V to 28V AC-Adapter Input Voltage Range Small 28-Pin Thin QFN Package (5mm x 5mm)
MAX1538
Ordering Information
PART MAX1538ETI TEMP RANGE -40C to +85C PIN-PACKAGE 28 Thin QFN
Typical Operating Circuit
ADAPTER
Applications
Notebook and Subnotebook Computers Internet Tablets Dual-Battery Portable Equipment
ACDET AIRDET ADPIN REVBLK EXTLD BATTERY CHARGER CHG_OUT CHGIN CHRG BATSEL RELRN OUT2 OUT1 OUT0
MAX1538
ADPBLK
VDD
Pin Configuration appears at end of data sheet.
MINVA CHGA CHGB DISB GND DISA BATB BATA BATTERY B BATTERY A BATSUP MINVB
________________________________________________________________ Maxim Integrated Products
1
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Power-Source Selector for Dual-Battery Systems MAX1538
ABSOLUTE MAXIMUM RATINGS
VEXTLD, VBATSUP, VADPIN, VBATA, VBATB, VCHGIN to GND .................................................-0.3V to +30V VADPPWR to GND...................................-0.3V to (VADPIN + 0.3V) VREVBLK, VADPBLK to GND ...................-0.3V to (VEXTLD + 0.3V) VCHGA, VCHGB, VDISBAT to GND ..........-0.3V to (VCHGIN + 0.3V) VDISA to GND..........................................-0.3V to (VBATA + 0.3V) VDISB to GND..........................................-0.3V to (VBATB + 0.3V) VDD, VCHRG, VBATSEL, VRELRN, VOUT0, VOUT1, VOUT2, VMINVA, VMINVB, VAIRDET, VACDET to GND..........-0.3V to +6V Continuous Power Dissipation (TA = +70C) 28-Pin Thin QFN 5mm x 5mm (derate 20.8mW/C above +70C) ..........................1666.7mW Operating Temperature Range MAX1538ETI ....................................................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C 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
(VBATA = VBATB = VCHGIN = 16.8V, CVDD= 1F, VMINVA = VMINVB = 0.93V, VEXTLD = VADPIN = 28V, VCHRG = VBATSEL = VRELRN = 0, CADPPWR = CREVBLK = CADPBLK = CDISBAT = CDISA = CDISB = CCHGA = CCHGB = 4.7nF, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER ADPIN, EXTLD Supply Voltage Range CHGIN, BATA, BATB and BATSUP Supply Voltage Range VADPIN = highest, VADPPWR = high VADPIN = highest, VADPPWR = low VBATA = highest, VDISA = high VBATA = highest, VDISA = low VBATB = highest, VDISB = high VBATB = highest, VDISB = low VBATSUP = highest ADPIN Quiescent Current (ADPIN Current When Not the Highest Voltage) BATA Quiescent Current (BATA Current When Not the Highest Voltage) BATB Quiescent Current (BATB Current When Not the Highest Voltage) EXTLD Quiescent Current VADPIN = 4.75V to 18V, no external load at VDD VBATA = 4.75V to 19V, no external load at VDD VBATB = 4.75V to 19V, no external load at VDD VADPPWR = high VADPPWR = low VDISA = high VDISA = low VDISB = high VDISB = low CONDITIONS MIN 4.75 4.75 21 23 21 24 21 24 18 0.01 2.6 3.9 7.0 3.9 7.0 3.0 0.02 0.03 3.1 6.1 TYP MAX 28.00 19.00 50 54 42 50 42 50 40 0.5 A 6 6.0 A 12 6.0 A 12 6.1 1.0 1.5 6.2 12.1 A A UNITS V V
ADPIN, BATA, BATB, BATSUP Quiescent Current (Current from the Highest Voltage Supply)
VBATA = 4.75V to 19V, VBATB = 4.75V to 19V, VBATSUP = 4.75V to 19V, VADPIN = 4.75V to 28V, no external load at VDD
A
Adapter selected (REVBLK or ADPBLK pins low) Adapter not selected (REVBLK and ADPBLK pins high) AC or airline state (CHGA, CHGB, and DISBAT pins high) Charge state (CHGA or CHGB pin low, DISBAT pin high) Discharge or relearn state (CHGA or CHGB pin low, DISBAT pin low)
CHGIN Quiescent Current
2
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Power-Source Selector for Dual-Battery Systems
ELECTRICAL CHARACTERISTICS (continued)
(VBATA = VBATB = VCHGIN = 16.8V, CVDD= 1F, VMINVA = VMINVB = 0.93V, VEXTLD = VADPIN = 28V, VCHRG = VBATSEL = VRELRN = 0, CADPPWR = CREVBLK = CADPBLK = CDISBAT = CDISA = CDISB = CCHGA = CCHGB = 4.7nF, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER LINEAR REGULATOR VDD Output Voltage VDD Power-Supply Rejection Ratio VDD Undervoltage Lockout COMPARATORS ACDET, AIRDET Input Voltage Range ACDET, AIRDET Input Bias Current ACDET, AIRDET Trip Threshold ACDET, AIRDET Hysteresis MINV_ Operating Voltage Range MINV_ Input Bias Current BAT_ Minimum Voltage Trip Threshold BAT_ Minimum Voltage Hysteresis BAT_ Pack Removal Detection Threshold BAT_ Pack Removal Hysteresis GATE DRIVERS (Note 1) ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Source Current (PMOS Turn-Off) ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Sink Current (PMOS Turn-On) ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Turn-On Clamp Voltage (VPIN to VSOURCE) VSOURCE = 15V, VPIN = 7.5V VSOURCE = 15V, VPIN = 13V VSOURCE = 15V, VPIN = 15V VSOURCE = 15V, VPIN = 9.5V VSOURCE = 8V to 19V (ADPPWR, REVBLK, and AOPBLK, VSOURCE = 8V to 28V) VSOURCE = 4.75V to 8V 18 3 20 10 -11.0 -8.00 60 mA 15 70 mA 55 -9.0 -7.0 V -3.65 VBAT_ falling 1.90 VMINV_ = 0.93V to 2.6V VMINV_ = 0.93V VBAT_ falling VMINV_ = 1.5V VMINV_ = 2.6V 0.93 -50 4.605 7.455 12.93 4.65 7.5 13 125 2.0 85 2.10 VAIRDET = VACDET = 3V Input falling 1.97 0 0.1 2.0 20 2.60 +50 4.695 7.545 13.07 mV V mV V 5.5 1 2.03 V A V mV V nA IVDD = 0 to 100A VBATA or VBATB = 5V to 19V, VADPIN = 5V VBATA = VBATB = 5V, VADPIN = 5V to 28V VBATA, VBATB, or VADPIN = 5V to 19V, sawtooth at 10V/s, other supplies = 12V Rising edge, relative to regulation point -55 1 -10 mV 3.270 3.3 3.330 1.0 1.0 mV / V V CONDITIONS MIN TYP MAX UNITS
MAX1538
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Power-Source Selector for Dual-Battery Systems MAX1538
ELECTRICAL CHARACTERISTICS (continued)
(VBATA = VBATB = VCHGIN = 16.8V, CVDD= 1F, VMINVA = VMINVB = 0.93V, VEXTLD = VADPIN = 28V, VCHRG = VBATSEL = VRELRN = 0, CADPPWR = CREVBLK = CADPBLK = CDISBAT = CDISA = CDISB = CCHGA = CCHGB = 4.7nF, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Turn-On Time ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Turn-Off Time STATE SELECTION INPUTS CHRG, BATSEL, RELRN Input Low Voltage CHRG, BATSEL, RELRN Input High Voltage CHRG, BATSEL, RELRN Input Leakage Current STATE OUTPUTS OUT0, OUT1, OUT2 Sink Current OUT0, OUT1, OUT2 Leakage Current TRANSITION TIMES MINV_ Comparator Delay AIRDET and ACDET Comparator Delay BAT_ Removal Comparator Delay Battery-Insertion Blanking Time State-Machine Delay MOSFET Turn-On Delay tTRANS 5 tBBLANK tMINV tADP VBAT_ = 5.5V to VBAT_ = 4.45V Falling edge with -20mV overdrive Falling edge with -20mV overdrive 13 5.5 2.7 10 21 50 7.5 10 31 11 6.0 s s s ms ns s VOUT_ = 5.5V VOUT_ = 0.4V VOUT_ = 5.5V 1 25 0.1 1 mA A VCHRG = VBATSEL = VRELRN = 5.5V 2.1 0.1 1 0.8 V V A SYMBOL CONDITIONS VSOURCE = 15V, VPIN = 13V to VPIN = 9V MIN TYP 0.3 MAX 0.88 UNITS s
VSOURCE = 15V, VPIN = 9V to VPIN = 13V
0.3
0.88
s
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Power-Source Selector for Dual-Battery Systems
ELECTRICAL CHARACTERISTICS
(VBATA = VBATB = VCHGIN = 16.8V, CVDD = 1F, VMINVA = VMINVB = 0.93V, VEXTLD = VADPIN = 28V, VCHRG = VBATSEL = VRELRN = 0, CADPPWR = CREVBLK = CADPBLK = CDISBAT = CDISA = CDISB = CCHGA = CCHGB = 4.7nF, TA = -40C to +85C, unless otherwise noted.) (Note 2)
PARAMETER ADPIN, EXTLD Supply Voltage Range CHGIN, BATA, BATB, and BATSUP Supply Voltage Range VADPIN = highest, VADPPWR = high VBATA = 4.75V to 19V, VBATB = 4.75V to 19V, VBATSUP = 4.75V to 19V, VADPIN = 4.75V to 28V, no external load at VDD VADPIN = highest, VADPPWR = low VBATA = highest, VDISA = high VBATA = highest, VDISA = low VBATB = highest, VDISB = high VBATB = highest, VDISB = low VBATSUP = highest ADPIN Quiescent Current (ADPIN Current When Not the Highest Voltage) BATA Quiescent Current (BATA Current When Not the Highest Voltage) BATB Quiescent Current (BATB Current When Not the Highest Voltage) EXTLD Quiescent Current VADPIN = 4.75V to 18V, no external load at VDD VBATA = 4.75V to 19V, no external load at VDD VBATB = 4.75V to 19V, no external load at VDD VADPPWR = high VADPPWR = low VDISA = high VDISA = low VDISB = high VDISB = low CONDITIONS MIN 4.75 4.75 MAX 28.00 19.00 50 54 42 50 42 50 40 1 A 9 7.5 A 16 7.5 A 16 9.5 1.0 1.5 10 18.5 A A A UNITS V V
MAX1538
ADPIN, BATA, BATB, BATSUP Quiescent Current (Current from the Highest Voltage Supply)
Adapter selected (REVBLK or ADPBLK pins low) Adapter not selected (REVBLK and ADPBLK pins high) AC or airline state (CHGA, CHGB, and DISBAT pins high) Charge state (CHGA or CHGB pin low, DISBAT pin high) Discharge or relearn state (CHGA or CHGB pin low, DISBAT pin low)
CHGIN Quiescent Current
LINEAR REGULATOR VDD Output Voltage VDD Undervoltage Lockout COMPARATORS ACDET, AIRDET Input Voltage Range ACDET, AIRDET Trip Threshold MINV_ Operating Voltage Range BAT_ Minimum Voltage Trip Threshold VMINV_ = 0.93V VBAT_ falling VMINV_ = 1.5V VMINV_ = 2.6V Input falling 0 1.94 0.93 4.59 7.4 12.86 5.5 2.06 2.60 4.72 7.6 13.14 V V V V IVDD = 0 to 100A Rising edge, relative to regulation point 3.270 -60 3.330 -10 V mV
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Power-Source Selector for Dual-Battery Systems MAX1538
ELECTRICAL CHARACTERISTICS (continued)
(VBATA = VBATB = VCHGIN = 16.8V, CVDD = 1F, VMINVA = VMINVB = 0.93V, VEXTLD = VADPIN = 28V, VCHRG = VBATSEL = VRELRN = 0, CADPPWR = CREVBLK = CADPBLK = CDISBAT = CDISA = CDISB = CCHGA = CCHGB = 4.7nF, TA = -40C to +85C, unless otherwise noted.) (Note 2)
PARAMETER BAT_ Pack Removal Detection Threshold GATE DRIVERS (Note 1) ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Source Current (PMOS Turn-Off) ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Sink Current (PMOS Turn-On) ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Turn-On Clamp Voltage (VPIN to VSOURCE) ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Turn-On Time ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, CHGB Turn-Off Time STATE SELECTION INPUTS CHRG, BATSEL, RELRN Input Low Voltage CHRG, BATSEL, RELRN Input High Voltage STATE OUTPUTS OUT0, OUT1, OUT2 Sink Current TRANSITION TIMES MINV_ Comparator Delay AIRDET and ACDET Comparator Delay Battery-Insertion Blanking Time MOSFET Turn-On Delay tMINV tADP tBBLANK tTRANS VBAT_ = 5.5V to VBAT_ = 4.45V Falling edge with -20mV overdrive 12 5 11 6 31 10 s s ms s VOUT_ = 0.4V VOUT_ = 5.5V 1 25 mA 2.1 0.8 V V VSOURCE = 15V, VPIN = 7.5V VSOURCE = 15V, VPIN = 13V VSOURCE = 15V, VPIN = 15V VSOURCE = 15V, VPIN = 9.5V VSOURCE = 8V to 19V (ADPPWR, REVBLK, and ADPBLK, VSOURCE = 8V to 28V) VSOURCE = 4.75V to 8V 18 mA 3 20 mA 10 -11.7 -8.00 -6.5 V -3.50 SYMBOL VBAT_ falling CONDITIONS MIN 1.88 MAX 2.12 UNITS V
VSOURCE = 15V, VPIN = 13V to VPIN = 9V
0.88
s
VSOURCE = 15V, VPIN = 9V to VPIN = 13V
0.88
s
Note 1: VPIN refers to the voltage of the driver output. VSOURCE refers to the power source for the driver. ADPPWR, REVBLK, ADPBLK, DISBAT, DISA, DISB, CHGA, and CHGB gate drivers correspond to sources at ADPIN, EXTLD, EXTLD, CHGIN, BATA, BATB, CHGIN, and CHGIN, respectively. Note 2: Guaranteed by design. Not production tested.
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Power-Source Selector for Dual-Battery Systems MAX1538
Typical Operating Characteristics
(Circuit of Figure 1. TA = +25C, unless otherwise noted.)
VDD LOAD REGULATION
MAX1538 toc01
VDD vs. TEMPERATURE
MAX1538 toc02
IBAT_ vs. VBAT_
30 25 20 15 10 5 BAT_ HIGHEST SUPPLY
MAX1538 toc03
3.299 3.298 3.297 3.296 VDD (V) 3.295 3.294 3.293 3.292 3.291 3.290 0 0.05 0.10 0.15
3.310
35 BATTERY INPUT CURRENT (A)
3.305
VDD (V)
3.300
3.295
3.290
3.285 0.20 -40 -20 0 20 40 60 80 VDD LOAD CURRENT (mA) TEMPERATURE (C)
0 4 6 8 10 12 14 16 BATTERY VOLTAGE (V)
IBAT_ vs. VBAT_
MAX1538 toc04
ADAPTER INSERTION
MAX1538 toc05
4.0 BAT_ NOT HIGHEST SUPPLY 3.5 BATTERY INPUT CURRENT (A) 3.0 2.5 2.0 1.5 1.0 0.5 0 0 5 10 15
VADPIN 20V VADPIN AND 10V VEXTLD VEXTLD VREVBLK 0V 20V V tADP 10V VREVBLK 0V VADPBLK 5V VOUT1 0V
ADPBLK
20
10.0s/div
BATTERY VOLTAGE (V)
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Power-Source Selector for Dual-Battery Systems MAX1538
Typical Operating Characteristics (continued)
(Circuit of Figure 1. TA = +25C, unless otherwise noted.)
BATTERY INSERTION
MAX1538 toc06
BATTERY REMOVAL
MAX1538 toc07
A 10V B SYSTEM LOAD = 3A 0V 0V VBATA VOUT0 (10V/div)
CONTACT BOUNCE 10V 0V 0V VBATA VOUT0 (10V/div)
10V VDISB (10V/div) 10V VDISA 0V 20V VBATB = 16.8V VBATA = 10V 10V VEXTLD 5.00ms/div 5.00ms/div A: CONTACT BOUNCE B: BATTERY INSERTION BLANKING TIME = 22ms VBATA = 10V
10V VDISB (10V/div) 10V VDISA 0V VBATB = 16.8V 20V VEXTLD 10V
BATTERY REMOVAL TIMING
MAX1538 toc08
SOURCE SELECTION CHANGE
10.2V 10V 9.8V 9.6V 10V 0V 10V INDUCTIVE KICK VDISA 0V 0V VOUT0 (10V/div) SYSTEM LOAD = 3A 2.00s/div CBATB = 1F VBATB AC-COUPLED (5V/div) VDISB VEXTLD
MAX1538 toc09
10V 0V 5V 0V VBATSEL VOUT0
5 x MINV tMINV (tADP FOR t TRANS ADAPTER REMOVAL TIMING)
VBATA = 16.8V BATTERY B REMOVED
10V VDISB (10V/div) 20V tTRANS VDISA 10V (10V/div)
SYSTEM LOAD = 3A
4.00s/div
SOURCE SELECTION CHANGE
MAX1538 toc10
10V 0V 5V 0V VBATSEL VOUT0
VDISB 10V (10V/div) 20V tTRANS INDUCTIVE KICK NO CAPACITOR AT BATB VBATB AC-COUPLED (5V/div) 2.00s/div VDISA 10V (10V/div)
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Power-Source Selector for Dual-Battery Systems
Typical Operating Characteristics (continued)
(Circuit of Figure 1. TA = +25C, unless otherwise noted.)
BREAK-BEFORE-MAKE TIMING
MAX1538 toc11
MAX1538
FIRST SOURCE INSERTION
MAX1538 toc12
5V OUT1 0V OUT2, OUT0
tTRANS 16V MOSFET TURN-OFF TIME 14V 12V MOSFET DRIVERS 10V 8V POWER-UP TIME
20V VADPIN 10V VREVBLK 0V 20V 10V 0V 200s/div VEXTLD
MOSFET TURN-ON TIME MOSFET FOR INITIAL DISCHARGE PATH MOSFET FOR FINAL DISCHARGE PATH 1.00s/div
Pin Description
PIN 1 2 3 4 5 6 7 8 9 10 11 NAME MINVA MINVB BATSEL RELRN CHRG OUT0 OUT1 OUT2 ACDET AIRDET ADPIN AC-Adapter Detection Input. When VACDET is greater than the ACDET trip threshold (2V typ), adapter presence is detected. Airline-Adapter Detection Input. When VAIRDET > 2V and VACDET < 2V, the airline-adapter presence is detected. Charging is disabled when an airline adapter is detected. Adapter Input. When VADPIN > VBATSUP, the MAX1538 is powered by ADPIN. ADPIN is the supply rail for the ADPPWR MOSFET driver. Adapter-Power P-Channel MOSFET Driver. Connect ADPPWR to the gate of P1 (Figure 1). P1 disconnects the adapter from the system during relearn mode. Exclude P1 and leave ADPPWR disconnected if relearn is not used. ADPPWR is driven relative to ADPIN. ADPPWR and REVBLK are driven with the same control signal. Gate Drive for the Reverse-Blocking P-Channel MOSFET. Connect REVBLK to the gate of P2 (Figure 1). P2 enables and disables the AC adapter's power path. REVBLK is driven relative to EXTLD. REVBLK and ADPPWR are driven with the same control signal. Selector-State Output. This open-drain output indicates the state of the MAX1538. See Table 1 for information on decoding. FUNCTION Minimum Battery A Voltage Set Point. Battery A discharge is prevented if VBATA has fallen below 5 x VMINVA. Minimum Battery B Voltage Set Point. Battery B discharge is prevented if VBATB has fallen below 5 x VMINVB. Battery-Selection Input. Drive to logic low to charge battery A or give discharge preference to battery A. Drive to logic high to charge battery B or give discharge preference to battery B. Battery-Relearn Logic-Level Input. Drive RELRN high to enable battery-relearn mode. Charge-Enable Logic-Level Input. Drive CHRG high to enable the charging path from the charger to the battery selected by BATSEL.
12
ADPPWR
13
REVBLK
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9
Power-Source Selector for Dual-Battery Systems MAX1538
Pin Description (continued)
PIN 14 15, 21 16 17 NAME ADPBLK N.C. EXTLD CHGIN FUNCTION Gate Drive for the Adapter-Blocking P-Channel MOSFET. Connect ADPBLK to the gate of P3 (Figure 1). P3 enables and disables the battery discharge path. ADPBLK is driven relative to EXTLD. ADPBLK and DISBAT are driven with the same control signal. Not Internally Connected External Load. EXTLD is the supply rail for REVBLK and ADPBLK. Charger Node Input. CHGIN is the supply rail for DISBAT, CHGA, and CHGB. Gate Drive for the Battery-Discharge P-Channel MOSFET. Connect DISBAT to the gate of P4 (Figure 2). P4 disconnects the battery from the system load when charging from a step-up converter. Exclude P4 and leave DISBAT disconnected if using a step-down charger. DISBAT is driven relative to CHGIN. DISBAT and ADPBLK are driven by the same control signal. Gate Drive for the Charge Battery A P-Channel MOSFET. Connect CHGA to the gate of P6 (Figure 1). P6 enables and disables the charge path into battery A. CHGA is driven relative to CHGIN. CHGA and DISA are driven by the same control signal. Gate Drive for the Charge Battery B P-Channel MOSFET. Connect CHGB to the gate of P7 (Figure 1). P7 enables and disables the charge path into battery B. CHGB is driven relative to CHGIN. CHGB and DISB are driven by the same control signal. Battery B Voltage Input. Battery undervoltage and absence is determined by measuring BATB. BATB is the supply rail for DISB. Gate Drive for the Discharge from Battery B P-Channel MOSFET. Connect DISB to the gate of P8 (Figure 1). P8 enables and disables the discharge path from battery B. DISB is driven relative to BATB. DISB and CHGB are driven by the same control signal. Gate Drive for the Discharge from Battery A P-Channel MOSFET. Connect DISA to the gate of P5 (Figure 1). P5 enables and disables the discharge path from battery A. DISA is driven relative to BATA. DISA and CHGA are driven by the same control signal. Battery A Voltage Input. Battery undervoltage and absence is determined by measuring BATA. BATA is the supply rail for DISA. BATSUP powers the MAX1538. Diode OR BATA and BATB to BATSUP externally. ADPIN is diode connected to BATSUP internally. Bypass with a 0.1F capacitor from BATSUP to GND. Ground Linear-Regulator Output. Bypass with a 1F capacitor from VDD to GND.
18
DISBAT
19
CHGA
20
CHGB
22
BATB
23
DISB
24
DISA
25 26 27 28
BATA BATSUP GND VDD
10
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Power-Source Selector for Dual-Battery Systems MAX1538
ADAPTER
R1 CADAPTER ACDET AIRDET FOR RELEARN P1 MODE ONLY ADPIN ADPPWR CHRG BATSEL RELRN R2 R3
STEP-DOWN CHARGER P2 SYSTEM LOAD CSYS CHARGER INPUT CHARGER OUTPUT CCHG OUT CHGIN P7 P6 CHGA CHGB DISB P8 P5 DISA BATB CBATB D1 D2 BATA BATSUP RSNS C2 P3 ADPBLK IN REVBLK EXTLD
MAX1538
LOGIC SUPPLY
OUT2 OUT1 OUT0 VDD R10 MINVA R11 GND MINVB R12
C1 0.1F
CBATA
C3 0.1F R13
BATTERY B
BATTERY A
Figure 1. Step-Down Typical Application Circuit
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11
Power-Source Selector for Dual-Battery Systems MAX1538
ADAPTER
R1 CADAPTER ACDET AIRDET FOR RELEARN P1 MODE ONLY ADPIN ADPPWR CHRG BATSEL RELRN LOGIC SUPPLY STEP-UP CHARGER R2 + R3 EXTERNAL AC/AIRDETECTION CIRCUIT OUT
MAX1538
IN OUT2 P2 REVBLK OUT1 OUT0 OUT EXTLD CSYS P3 ADPBLK VDD R10 MINVA R11 CHGIN R12 P7 P6 CHGA CHGB DISB GND P8 P5 DISA BATB MINVB R13 C1 1F
CHARGER INPUT CHARGER OUTPUT CCHG SYSTEM LOAD C2
P4
DISBAT
CBATB
D1
BATA
BATSUP C3 0.1F
CBATA
D2
BATTERY B
BATTERY A
Figure 2. Typical Application Circuit for Step-Up/Step-Down Charger
12
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Power-Source Selector for Dual-Battery Systems MAX1538
4R BATB R 0.4V
BATTERY B UNDERVOLTAGE LATCH Q S
ADPIN ADPPWR
R MINVB 4R BATA R 0.4V
Q EXTLD REVBLK
BATTERY A UNDERVOLTAGE LATCH Q S
ADPBLK
R MINVA
Q
CHGIN DISBAT
ACDET
CHGA 2V STATE MACHINE
CHGB AIRDET CHRG BATSEL RELRN BATSUP VDD REF GND LDO DISB ADPIN BATB BATA
DISA
OUT0 OUT1 OUT2
MAX1538
N N N
Figure 3. Functional Diagram ______________________________________________________________________________________ 13
Power-Source Selector for Dual-Battery Systems MAX1538
Detailed Description
The MAX1538 performs power path selection between an adapter input and two batteries, relieving the host system from the burden of real-time response to powersource changes. The integrated selector implements a fixed break-before-make timer to ensure that power sources are not connected together and yet the load is not left unserviced. The MAX1538 monitors battery and adapter state and presence to determine which source to select and whether to charge the battery. Logic inputs CHRG, BATSEL, and RELRN allow the host to enable/disable charging, select which battery to use, and impose battery discharge even with adapter presence. The MAX1538 automatically detects airline adapters and prevents charging when an airline adapter is detected. Open-drain logic outputs OUT2, OUT1, and OUT0 indicate the state of the selector so the host can properly respond. The MAX1538 can be configured for use with a stepdown battery charger, as shown in Figure 1, or with a step-up/step-down battery charger, as shown in Figure 2. The minimum MAX1538 system requires only six MOSFETs. The MAX1538 provides relearn-mode support with the addition of P1. Relearn mode allows the system to relearn the battery's capacity without user intervention. Table 1 summarizes the possible states and configurations of the MAX1538.
Table 1. MAX1538 State Table
SOURCE STATE Battery Adapter A X X N X B X X X N CHG LOGIC INPUTS BATSEL RELRN MOSFET STATE (See Figure 4) OUT2 OUT1 System (ADPPWR and REVBLK) On On Off Off On X X X X X X X 0 X 1 X X On Off Off Off Battery (ADPBLK and DISBAT) Off Off On On Off Off On On Off BATT A (CHGA and DISA) On Off On Off Off Off On Off Off BATT B (CHGB and DISB) Off On Off On Off Off Off On Off OUT0 0 1 0 1 0 1 0 1 0 STATE
AC AC AC AC AC AIR Absent Absent Absent Absent Absent Legend AC AIR Absent
1 1 X X Otherwise
0 0 1 1
0 1 0 1
1 1 1 1 0 0 0 0 0
1 1 0 0 1 1 0 0 0
Charge A Charge B Relearn A Relearn B AC adapter Airline Discharge A Discharge B Idle
X N N X U U
X X U N N U
X X X X X X
AC adapter is present. VACDET and VAIRDET are both above 2V. Airline adapter is present. VACDET is below 2V and VAIRDET is above 2V. External adapter is absent. VACDET and VAIRDET are both below 2V. N N indicates the battery is normal. The battery is normal when it has not tripped the undervoltage latch (5 x VMINV_). See the Battery Presence and Undervoltage Detection section. U indicates the battery has tripped the undervoltage comparator. An undervoltage battery is detected when VBAT_ goes below 5 x VMINV_. See the Battery Presence and Undervoltage Detection section. Otherwise X X X X X Otherwise covers all cases not explicitly shown elsewhere in the table. X indicates don't care. The output does not depend on any inputs labeled X.
U
14
______________________________________________________________________________________
Power-Source Selector for Dual-Battery Systems
ADAPTER ADAPTER ADAPTER
ADAPTER SWITCH SYSTEM BATTERY SWITCH CHARGER
ADAPTER SWITCH SYSTEM BATTERY SWITCH CHARGER
ADAPTER SWITCH SYSTEM BATTERY SWITCH CHARGER
not allowed until the battery is removed or the charge path to the battery is selected. Battery removal is detected when VBAT_ falls below 2V. For correct detection of battery removal, ensure that the leakage current into BAT_ is lower than the leakage current out of BAT_ so that BAT_ falls below 2V when the battery is removed. The contributors to leakage current into BAT_ are D1, D2, P6, and P7.
MAX1538
Battery Relearn Mode
The MAX1538 implements a battery relearn mode, which allows for host-device manufacturers to implement a mode for coulomb-counting fuel gauges (such as the MAX1781) to measure battery capacity without user intervention. In battery relearn mode, the AC adapter is switched off and battery discharge is selected. In this implementation, the host system could prompt users when their battery capacity becomes inaccurate, use the host system as a load to discharge the battery, and then recharge the battery fully. Coulomb-counting fuel-gauge accuracy is increased after a relearning cycle. Battery relearn mode requires the addition of MOSFET P1, which blocks current from the adapter to the system. To enable relearn mode, drive RELRN high and drive BATSEL low to relearn battery A or high to relearn battery B. Relearn mode overrides the functionality of the CHG pin. Battery relearn mode does not occur when the selected battery's undervoltage latch has been set, or when the selector is in airline mode (see the Airline Mode and AC Adapter section.) The RELRN pin only applies when an AC adapter is present. If the AC adapter is absent and RELRN is ignored, OUT[2:1] = 10 when the MAX1538 is in battery relearn mode. If CHG = 0, only OUT2 is needed to indicate that the MAX1538 was properly placed in relearn mode. If the selected battery trips the undervoltage latch when in relearn mode, the AC adapter is switched in without causing a crash to the system. OUT2 can indicate that the relearn cycle is terminated due to battery undervoltage. Typically, after the host system performs a battery relearn cycle, it either charges the discharged battery or begins a relearn cycle on the other battery. To switch to charge mode, drive RELRN low and CHG high. Since RELRN overrides CHG, in many applications it is best to permanently keep CHG high and reduce the IO needed to control the selector. When the AC adapter is available, it is used as the power source for EXTLD unless the RELRN pin is high. In this state, the charger can be enabled and a battery charged.
"A" SWITCH
"B" "A" SWITCH SWITCH
"B" "A" SWITCH SWITCH
"B" SWITCH
CHARGE
Figure 4. MAX1538 Selection States
The MAX1538 determines battery absence and undervoltage and does not allow discharge from an undervoltage battery. A battery is considered undervoltage when VBAT_ < 5 x VMINV_, and remains classified as undervoltage until VBAT_ falls below 2V and again rises above 5 x V MINV . The undervoltage latch is also cleared when the charge path is enabled. Set the battery undervoltage threshold using resistive voltagedividers R10, R11, R12, and R13, as shown in Figure 1. The corresponding undervoltage threshold is: VBATA _ Undervoltage = 5 x VDD x R11 R10 + R11 R13 R12 + R13
VBATB _ Undervoltage = 5 x VDD x
To minimize error, use 1% or better accuracy divider resistors, and ensure that the impedance of the divider results in a current about 100 times the MINV_ input bias current at the MINV_ threshold voltage. To optimize error due to 50nA input bias current at MINV_ and minimize current consumption, typically choose resistors (R10 + R11) or (R12 + R13) smaller than 600k. Since batteries often exhibit large changes in their terminal voltage when a load current is removed, further discharge after the undervoltage latch has been set is
BATTERY A
BATTERY B
DISCHARGE/ RELEARN
______________________________________________________________________________________
BATTERY A
Battery Presence and Undervoltage Detection
BATTERY B
AC/AIR
BATTERY A
BATTERY B
15
Power-Source Selector for Dual-Battery Systems MAX1538
Airline Mode and AC Adapter
The MAX1538 provides compatibility with airline adapters. For airplane safety, the use of an airline adapter requires that the battery charger or charge path is disabled. The MAX1538 disables the charge path when an airline adapter is detected. In airline mode, ADPPWR and REVBLK drive P1 and P2 on, and all other MOSFETs are off, regardless of the state of RELRN, CHG, BATSEL, or the batteries. If the AC threshold is above the airline threshold, select a resistive voltage-divider (as shown in Figure 1) according to the following equations: VAC _ Threshold = VACDET _ Threshold x R1+ R2 + R3 R3 R1+ R2 + R3 R2 + R3 the adapter voltage is between V AC_Threshold and VAIR_Threshold. To minimize error, use 1% accuracy or better divider resistors, and ensure that the impedance of the divider results in a current about 100 times the ACDET and AIRDET input bias current. To optimize error due to 1A input bias current at ACDET/AIRDET and minimize current consumption, typically choose R3 less than 20k. See the Adapter Removal Debouncing section for more information regarding R1, R2, and R3. Short R2 to disable airline-adapter mode. Optionally, an external circuit can be implemented to determine the presence of an AC/airline adapter. The circuit in Figure 5 provides fast detection of an airline adapter, yet allows external circuitry to discriminate between airline and AC adapters. If VAC_Threshold < V AIR_Threshold, this circuit must be used for airlineadapter detection. Other permutations that directly drive AIRDET instead do not work properly on the MAX1538 because adapter removal is not detected fast enough, causing the system load to crash. OUT[2:0] = 011 if the MAX1538 is in airline-adapter mode. If RELRN = 0 and CHG = 0, only OUT[1:0] are necessary to indicate airline-adapter mode.
ADAPTER INSERTION
VAir _ Threshold = VAIRDET _ Threshold x
where VACDET_Threshold and VAIRDET_Threshold are typically 2.0V (see the Electrical Characteristics). An AC adapter is detected when the adapter voltage is above VAC_Threshold, and an airline adapter is detected when
ADAPTER
R1 R2 + R3
EXTERNAL AC/AIRLINE DETECTION CIRCUIT OUT ACDET MUST WAIT ADPIN
ACDET AIRDET ADPIN ADPPWR
FOR AC ADAPTER FOR AIRLINE ADAPTER ACDET
P1
MAX1538
P2 REVBLK EXTLD
ADAPTER REMOVAL
ACDET MAY OCCUR BEFORE OR AFTER ADPIN FOR AC ADAPTER FOR AIRLINE ADAPTER
ADPIN
ACDET
Figure 5. Using an External Adapter Detection Circuit 16 ______________________________________________________________________________________
Power-Source Selector for Dual-Battery Systems
CHG Control
Toggle CHG to enable the charge path to the battery. Charge control is overridden by RELRN (see the Battery Relearn Mode section) or airline mode (see the Airline Mode and AC Adapter section). When CHG is enabled, the MAX1538 connects the selected battery (BATSEL = 0 for battery A and BATSEL = 1 for battery B) to the charger. OUT[2:1] = 11 if the MAX1538 is in charge mode. When the charge path is enabled, the corresponding battery undervoltage latch is cleared. This allows charging of protected battery packs. In typical applications, connect CHRG to VDD to reduce the system I/O. case the system holdup capacitor is not large enough to sustain the system load. Battery insertion is automatically debounced using the battery-insertion blanking time (tBBLANK). A battery is not discharged unless the battery has been above the 5 x VMINV threshold for 21ms (typ). After tBBLANK is expired, VBAT_ must exceed 5 x VMINV_ or the battery is detected as undervoltage.
MAX1538
Applications Information
MOSFET Selection
Select P-channel MOSFETs P1-P8 according to their power dissipation, R DSON , and gate charge. Each MOSFET must be rated for the full system load current. Additionally, the battery discharge MOSFETs (P3, P5, P6, P7, and P8) should be selected with low on-resistance for high discharge efficiency. Since for any given switch configuration at least half of the MOSFETs are off, dual MOSFETs can be used without reducing the effective MOSFET power dissipation. When using dual
ADAPTER
Single Transition Break-Before-Make Selection
The MAX1538 guarantees that no supplies are connected to each other during any transition by implementing a fixed delay time (tTRANS, the break-before-make transition timer). This is necessary as the batteries have very low impedances, and momentarily shorting batteries together can cause hundreds of amps to flow. For example, when adapter removal is detected, ADPPWR and REVBLK begin to turn off less than 10s before ADPBLK and DISBAT begin to turn on, connecting the appropriate battery. For example, upon switching from one battery to another, DISA and CHGA begin turning off less than 10s before DISB and CHGB begin to turn on. To guarantee a break-before-make time, ensure that the turn-off time of the MOSFETs is smaller than tTRANS (see the MOSFET Selection section). The MAX1538 also guarantees that any change does not cause unnecessary power-source transitions. When switching from battery to battery; battery to adapter; or adapter to battery because of adapter or battery insertion or removal, or due to a change at BATSEL, a single set of MOSFETs are turned off followed by another set of MOSFETs turned on. No additional transitions are necessary. The only exception occurs when RELRN is high and the adapter is inserted because it is first detected as an airline adapter and later detected as an AC adapter. This results in a transition from discharge mode to AC mode, followed by a transition from AC mode to relearn mode. Although this extra transition is generally harmless, it can be avoided by disabling relearn mode when the adapter is absent.
ADPIN FOR RELEARN MODE ONLY P1 ADPPWR
MAX1538
STEP-DOWN BATTERY CHARGER SYSTEM LOAD IN P2 REVBLK EXTLD P3 OUT DUAL FDS4935A CHGIN DUAL FDS4935A P7 P6 ADPBLK
CHGA CHGB DISB
DUAL FDS4935A
P8
P5
DISA BATB BATA
Blanking
The MAX1538 implements sophisticated blanking at the adapter and the batteries to correctly determine battery/adapter insertion and removal. Logic inputs CHRG, RELRN, and BATSEL should be debounced to ensure that fast repetitive transitions do not occur, in which
BATTERY B
BATTERY A
Figure 6. Optimal Use of Power Dissipation Using Dual MOSFETs ______________________________________________________________________________________ 17
Power-Source Selector for Dual-Battery Systems
MOSFETs, they should be paired as shown in Figure 6 for optimal power dissipation. The MAX1538 provides asymmetric MOSFET gate drive, typically turning MOSFETs on faster than they are turned off. The tTRANS timer ensures that the MOSFETs that are turning on begin to turn on 10s after those MOSFETs that are turning off begin to turn off. Choose MOSFETs with low enough gate charge that all off-transitioning MOSFETs turn off before any on-transitioning MOSFET turns on. Use the following equations to estimate the worst-case turn-on and turn-off times: t ON = QG V1 V2 QG + = x 0.93k I VG OFF1 IOFF2 VG 5V QG QG x = x 0.25k VG ION VG
MAX1538
slows down as the MOSFET approaches off. See the Typical Operating Characteristics for a scope shot showing MAX1538 turn-on and turn-off times when driving FDS6679 MOSFETs. The MAX1538 typically turns the FDS6679 on in 0.7s and off in 1s.
Combining the MAX1538 with a Charger
To configure the MAX1538 for use with a step-down charger, use the circuit of Figure 7. Connect the charger's power input to EXTLD. Do not connect the charger's power input to ADPIN. This ensures that the charger does not bias ADPIN through its high-side MOSFET.
System Holdup Capacitor
CSYS must be capable of sustaining the maximum system load during the transition time between source selection. Size the capacitor so that: 5 x VMINV - (tMINV + t TRANS + t ON ) x ISYS _ MAX CSYS > VSYS _ MIN
t ON =
where tON is the turn-on time, tOFF is the turn-off time, QG is the MOSFET's total gate charge specified at voltage VG, IOFF1 is the 18mA (min) gate current when driving the gate from 7.5V gate drive to 2V gate drive, V1 is the voltage change during the 18mA gate drive (5.5V), IOFF2 is 3mA gate current when driving the gate from 2V to 0V, V2 is the 2V change, and ION is the turn-on current. The MAX1538's gate-drive current is nonlinear and is a function of gate voltage. For example, the gate driver
where tMINV is the battery undervoltage comparator delay, t TRANS is the fixed time between switching MOSFETs off and switching MOSFETs on, tON is the time to turn a MOSFET on (see the MOSFET Selection section), VMINV is the lower of VMINVA and VMINVB, ISYS_MAX is the maximum system load, VSYS_MIN is the minimum allowable system voltage before system
ADAPTER
CADAPTER 1F
MAX1538
ADPIN
MAX1908 MAX1909 OR MAX1535
SYSTEM LOAD CSYS CSSN C2
DCIN P2 CSSP REVBLK EXTLD P3 BATT ADPBLK
CHGIN
Figure 7. Combining the MAX1538 with a Charger 18 ______________________________________________________________________________________
Power-Source Selector for Dual-Battery Systems MAX1538
OTHER POWER SOURCE 5 x VMINV OR AC/AIR THRESHOLD
EXTLD
MAX1538
VSYS_MIN tMINV OR tADP tOFF ADPBLK/REVBLK tTRANS REVBLK/ADPBLK tON
CSOURCE ISOURCE PARASITIC INDUCTANCE (LSOURCE)
TO BATTERY OR ADAPTER
Figure 8. System Holdup Capacitor Timing
Figure 9. Inductive Kick Upon Source Disconnect
crash, and CSYS is the total system holdup capacitance, which does not need to be near the MAX1538. The timing related to the system holdup capacitance is shown in Figure 8. Charger output capacitance contributes to CSYS for the step-down charger topology (Figure 1), but not for the step-up/step-down charger topology (Figure 2).
Inductive "Kick"
When the adapter or a battery is delivering a significant current to the system and that path is disabled (typically to enable another path), a voltage spike is generated at the source. This is due to a parasitic inductance shown in Figure 9. When the adapter is disconnected, a positive voltage spike occurs at ADPIN. When a discharging battery is disconnected, a positive voltage spike occurs at BAT_. Connect a capacitor from BAT_ or ADPIN to GND to limit this inductive kick. Choose the source capacitance according to the following equation: CSOURCE > LSOURCE x ISYS _ MAX 302 - VSOURCE
2 2
Leakage Current into BAT_
Leakage current into BATA or BATB can interfere with proper battery-removal detection. D1 and D2 must be low leakage to ensure that battery removal is properly detected. Choose MOSFETs P6 and P7 with low offleakage current. Board leakage current can also be a problem. For example, neighbor pins BATA and BATSUP should have greater than 50M impedance between each other. Proper battery-removal detection requires that: IBoard + IDS _ OFF(P6) + IDS _ OFF(P7) + ID1_ leakage + ID2 _ leakage < IBAT _ Sink @ 2V where IBoard is board leakage current, IDS_OFF is the off-leakage current of MOSFETs P6 and P7, ID_Leakage is the reverse leakage current of the diodes, and IBAT_Sink@2V is the BAT_ leakage current at 2V (0.4A; see the Typical Operating Characteristics).
where V SOURCE is the maximum DC voltage of the source in question, ISYS_MAX is the maximum system load, and L SOURCE (parasitic inductance) and CSOURCE are shown in Figure 9. During battery charge, the voltage spike during battery disconnect is negative. To ensure that this negative voltage spike does not go below 0V, choose CBAT_ according to the following equation: LBAT _ x ICHG _ MAX VBAT _ _ MIN
2 2
CBAT _ >
______________________________________________________________________________________
19
Power-Source Selector for Dual-Battery Systems MAX1538
where V BAT__MIN is the minimum battery voltage, ICHG_MAX is the maximum charge current, and LBAT_ is the battery's inductance. CBAT_ values of 0.01F are adequate for typical applications. Adding capacitance at BAT_ pins lengthens the time needed to detect battery removal. See the Battery-Absence-Detection Delay section.
Layout
The MAX1538 selector fits in a very small layout. Ensure that C1 is placed close to V DD and GND. Connect the paddle to GND directly under the IC. A complete layout example is shown in Figure 10. Because BATA and BATB are high-impedance nodes, prevent leakage current between BATA/BATB and other high-voltage sources by carefully routing traces. Note that flux remaining on the board can significantly contribute to leakage current. See the Leakage Current into BAT_ section. Minimize parasitic inductance in the BATA and BATB path to reduce inductive kick during battery disconnect. This reduces the capacitance requirement at BATA and BATB.
Adapter Removal Debouncing
Upon adapter removal the adapter's connector may bounce. To avoid false detection of adapter reinsertion select R1, R2, and R3 according to the following equation:
R1 + R2 + R3 < V_ Threshold x tBounce C ADPIN x VAdapter - V_ Threshold
(
)
where VAdapter is the AC-adapter voltage when removing an AC adapter and airline-adapter voltage when removing an airline adapter, CADPIN is the capacitance at ADPIN, and tBounce is the 5ms debounce time. See the Airline Mode and AC Adapter section for a definition of V_Threshold.
Pin Configuration
BATSUP
Battery-Absence-Detection Delay
When a selected battery is removed, the system load quickly pulls BAT_ below 5 x V MINV_ and another source is selected. The battery is considered present and undervoltage until VBAT_ falls below 2V. Although another power source is quickly switched to the system load, capacitance at BAT_ (see the Inductive "Kick" section) delays the detection of the removed battery. If another battery is inserted before this delay has passed, it is considered undervoltage. Calculate the delay using the following equation: t Absence _ delay = 19V x CBAT _ IBAT
*EXPOSED PADDLE MINVA 1 MINVB 2 BATSEL 3 RELRN 4 CHRG 5 OUT0 6 OUT1 7
28 27 26 25 24 23 22
21 N.C. 20 CHGB 19 CHGA
MAX1538 *
BATB
18 DISBAT 17 CHGIN 16 EXTLD 15 N.C.
BATA
DISA ADPPWR
8 OUT2
9 ACDET
10 11 12 13 14 AIRDET ADPIN REVBLK ADPBLK
THIN QFN (5mm x 5mm)
where IBAT_ is the 3.9A BAT_ quiescent current (due to a 5M internal resistor), and CBAT_ is the capacitance from BAT_ to GND. When CBAT_ = 1F, tAbsence_delay corresponds to a 5s time constant. If this time is unacceptable, use a smaller capacitance or connect a resistor or current sink from BAT_ to GND.
Chip Information
TRANSISTOR COUNT: 5431 PROCESS: BiCMOS
20
______________________________________________________________________________________
DISB
GND
VDD
GND
CBATB
BATTERY B 1 P8 8 5 4
VDD
GND
BATSUP
BATA
DISA
DISB
GND R11 MINVA 1 MINVB 2 BATSEL 3 RELRN 4 CHRG 5 OUT0 6 OUT1 7 15 N.C. * EXPOSED PADDLE 16 EXTLD 17 CHGIN 19 CHGA 20 CHGB 21 N.C. R10
28 27 26 25 24 23 22
MAX1538
18 DISBAT
BATB
OUT2
ACDET
AIRDET
ADPIN
REVBLK
GND
R2 R1
R3
ADPPWR
ADPBLK
Figure 10. MAX1538 Layout Example
2 6 P7 3 7 3 7 2 P5 6 CBATA 4 P6 5 8 1 CHARGER C1
8 7 6 5
CBATSUP
GND
BATTERY A
ADAPTER
8
9
10 11 12 13 14
P3 P2
1
2
3
4
CADAPTER
MAX1538
______________________________________________________________________________________
GND SYSTEM
Power-Source Selector for Dual-Battery Systems
21
Power-Source Selector for Dual-Battery Systems MAX1538
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.)
0.15 C A
D2
C L
D
b D2/2
0.10 M C A B
PIN # 1 I.D.
D/2
0.15 C B
k
PIN # 1 I.D. 0.35x45
E/2 E2/2 E (NE-1) X e
C L
E2
k L
DETAIL A
e (ND-1) X e
C L
C L
L e 0.10 C A 0.08 C e
L
C
A1 A3
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE 16, 20, 28, 32L, QFN THIN, 5x5x0.8 mm
DOCUMENT CONTROL NO. REV.
APPROVAL
21-0140
C
1 2
COMMON DIMENSIONS
EXPOSED PAD VARIATIONS
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. 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. 10. WARPAGE SHALL NOT EXCEED 0.10 mm.
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE 16, 20, 28, 32L, QFN THIN, 5x5x0.8 mm
DOCUMENT CONTROL NO. REV.
APPROVAL
21-0140
C
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.
22 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
QFN THIN.EPS

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