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LTC1479 PowerPath Controller for Dual Battery Systems
FEATURES
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DESCRIPTION
The LTC (R)1479 is the "heart" of a total power management solution for single and dual battery notebook computers and other portable equipment. The LTC1479 directs power from up to two battery packs and a DC power source to the input of the main system switching regulator. It works in concert with related LTC power management products (e.g. LTC1435, LT (R)1511, etc.) to create a total system solution; starting from the batteries and the DC power source, and ending at the input of each of the computer's complex loads. A system-provided power management P monitors and actively directs the LTC1479. The LTC1479 uses low loss N-channel MOSFET switches to direct power from three main sources. An adaptive current limiting scheme reduces capacitor and battery inrush current by controlling the gates of the MOSFET switches during transitions. The LTC1479 interfaces directly to the LT1510, LT1511 and LT1620/LTC1435 battery charging circuits.
, LTC and LT are registered trademarks of Linear Technology Corporation.
PowerPath is a trademark of Linear Technology Corporation.
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Complete Power Path Management for Two Batteries, DC Power Source, Charger and Backup Compatible with Li-Ion, NiCd, NiMH and Lead-Acid Battery Chemistries "3-Diode" Mode Ensures Powers is Available under "Cold Start" Conditions All N-Channel Switching Reduces Power Losses Capacitor and Battery Inrush Current Limited "Seamless" Switching Between Power Sources Independent Charging and Monitoring of Two Battery Packs New, Small Footprint, 36-Lead SSOP Package
APPLICATIONS
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Notebook Computer Power Management Portable Instruments Handheld Terminals Portable Medical Equipment Portable Industrial Control Equipment
TYPICAL APPLICATION
Dual Battery PowerPathTM Controller System Block Diagram
DCIN SW A/B SW C/D SW E/F SW G BAT2 BATTERY CHARGER (LT1510/LT1511/ LT1620/LTC1435) BACKUP REGULATOR (LT1304) POWER MANAGEMENT P SW H HIGH EFFICIENCY DC/DC SWITCHING REGULATOR (LTC1435/LTC1438 ETC.)
AC ADAPTER
RSENSE
BAT1
LTC1479 PowerPath CONTROLLER
STATUS & CONTROL
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CIN
5V
1479 TA01
1
LTC1479
ABSOLUTE MAXIMUM RATINGS
DCIN, BAT1, BAT2 Supply Voltages .......... - 0.3V to 32V SENSE +, SENSE -, VBAT, V + ..................... - 0.3V to 32V GA, GB, GC, GD, GE, GF, GG, GH .............. - 0.3V to 42V SAB, SCD, SEF, SG, SH ............................ - 0.3V to 32V SW, VGG ................................................... - 0.3V to 42V DCDIV, BDIV ............................................ - 0.3V to 5.5V All Logic Inputs (Note 1).......................... - 0.3V to 7.5V All Logic Outputs (Note 1) ....................... - 0.3V to 7.5V VCC Regulator Output Current ................................ 1mA VCCP Regulator Output Current .............................. 1mA V + Output Current .................................................. 1mA VGG Regulator Output Current ............................ 100A Operating Temperature LTC1479CG ............................................. 0C to 70C LTC1479IG ........................................ - 40C to 85C Junction Temperature........................................... 125C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
PACKAGE/ORDER INFORMATION
TOP VIEW DCIN DCDIV LOBAT GA SAB GB GC SCD GD 1 2 3 4 5 6 7 8 9 36 VBKUP 35 BAT1 34 BAT2 33 BDIV 32 VBAT 31 CHGMON 30 BATSEL 29 GG 28 SG 27 GH 26 SH 25 DCINGOOD 24 DCIN/BAT 23 BATDIS 22 3DM 21 CHGSEL 20 VCCP 19 GND
ORDER PART NUMBER LTC1479CG LTC1479IG
GE 10 SEF 11 GF 12 SENSE + 13 SENSE - 14 VCC 15 VGG 16 V+ 17
SW 18
G PACKAGE (209 mils) 36-LEAD PLASTIC SSOP
TJMAX = 100C, JA = 95C/ W
Consult factory for Military grade parts.
DC ELECTRICAL CHARACTERISTICS
VDCIN = 25V, VBAT1 = 16V, VBAT2 = 12V, TA = 25C unless otherwise noted. (Note 2)
SYMBOL VDCIN VBAT1 VBAT2 VBKUP IDCIN IVBAT1 IVBAT2 IVBKUP VCCP VCC VGG VUVLO VUVLOHYS PARAMETER DCIN Operating Range Battery 1 Operating Range Battery 2 Operating Range Backup Operating Range DCIN Operating Current Battery 1 Operating Current Battery 2 Operating Current Backup Operating Current VCCP Regulator Output Voltage VCC Regulator Output Voltage VGG Gate Supply Voltage UV Lockout Threshold UV Lockout Hysteresis CONDITIONS (Mode 1) DCIN Selected (Mode 5) Battery 1 Selected (Mode 6) Battery 2 Selected (Mode 8) Backup Operation (Mode 1) DCIN Selected (Mode 5) Battery 1 Selected (Mode 6) Battery 2 Selected (Mode 8) Backup Operation (VBKUP = 6V) (Modes 1, 5, 6) DCIN, Battery 1 or Battery 2 Selected (Modes 1, 5, 6) DCIN, Battery 1 or Battery 2 Selected (Modes 1, 5, 6) DCIN, Battery 1 or Battery 2 Selected (Mode 9) No Power, VBATX Falling from 12V (Mode 9) No Power, VBATX Rising from 1V
q q q
MIN 6 6 6 6
TYP
MAX 28 28 28 28
UNITS V V V V A A A A V V V V V
Power Supplies
175 150 150 40 4.0 3.3 34.0 4.0 0.2 4.8 3.6 36.3 4.5 0.5
500 500 500 100 6.0 3.9 40.0 5.0 1.0
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LTC1479
DC ELECTRICAL CHARACTERISTICS
VDCIN = 25V, VBAT1 = 16V, VBAT2 = 12V, TA = 25C unless otherwise noted. (Note 2)
SYMBOL VTHDCDIV PARAMETER DCDIV Threshold Voltage CONDITIONS (Mode 1) VDCDIV Rising from 1V to 1.5V (Mode 1) VDCDIV Falling from 1.5V to 1V (Mode 1) VDCDIV = 1.5V (Mode 1) VDCDIV = 1V, IDCINGOOD = 100A (Mode 1) VDCDIV = 1.5V, VDCINGOOD = 0V (Mode 1) VDCDIV = 1.5V, VDCINGOOD = 7V (Modes 5, 6) VBDIV Falling from 1.5V to 1V (Modes 5, 6) VBDIV Rising from 1V to 1.5V (Modes 5, 6) VBDIV = 1.5V (Modes 5, 6) VBDIV = 1V, ILOBAT = 100A (Modes 5, 6) VBDIV = 1.5V, VLOBAT = 7V (Modes 5, 6) Each Switch Tested Independently (Modes 5, 6) Each Switch Tested Independently 5.0 4.5 5 5
q q q
MIN 1.190 10 0 1
TYP 1.215 35 20 0.1 2
MAX 1.240 50 0.4 6 1
UNITS V mV nA V A A V mV nA V A A V V V A A V A A A mA mA
DCIN Good Monitor VHYSDCDIV DCDIV Hysteresis Voltage IBIASDCDIV DCDIV Input Bias Current VLODCGD IPUDCGD ILKGDCGD VTHLOBAT IBIASBDIV VLOLOBAT ILKGLOBAT DCINGOOD Output Low Voltage DCINGOOD Pull-Up Current DCINGOOD Leakage Current Low-Battery Threshold Voltage BDIV Input Bias Current LOBAT Output Low Voltage LOBAT Output Leakage Current
Battery Monitor 1.190 10 0 200 1.215 35 20 0.1 400 0.4 1 800 1 5.5 5.2 0 15 15 0.20 100 100 100 3 3 50 150 250 1
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1.240 50
VHYSLOBAT Low-Battery Hysteresis Voltage
RONBATSW Battery Switch ON Resistance ILKGBATSW Battery Switch OFF Leakage Gate Drivers VGS(ON) VGS(OFF) IBSENSE+ IBSENSE- VSENSE IPDSAB IPDSCD IPDSEF IPDSG IPDSH RONCMON ILKGCMON VHIDIGIN VLODIGIN IHIDIGIN ILODIGIN IPUDIGIN
Gate-to-Source ON Voltage (GA to GF) (Modes 1, 2, 4, 5, 6) IGS = -1A Gate-to-Source ON Voltage (GG, GH) (Modes 2, 4) IGS = -1A Gate-to-Source OFF Voltage SENSE + Input Bias Current SENSE - Input Bias Current Inrush Current Limit Sense Voltage SAB Pull-Down Current SCD Pull-Down Current SEF Pull-Down Current SG Pull-Down Current SH Pull-Down Current CHGMON Switch ON Resistance CHGMON Switch OFF Leakage Input High Voltage Input Low Voltage Input Leakage Current Input Leakage Current Input Pull-Up Current (Modes 1, 2, 4, 5, 6) IGS = 100A (Modes 1, 5, 6) (Modes 1, 5, 6) (Modes 1, 5, 6) (Modes 5, 6) VSAB = 10V (Mode 1) VSCD = 10V (Mode 1) VSEF = 10V (Mode 1) VSG = 10V (Mode 1) VSH = 10V (Modes 5, 6) Each Switch Tested Independently (Modes 5, 6) Each Switch Tested Independently (Mode 1) All Digital Inputs (Mode 1) All Digital Inputs (Mode 1) All Digital Inputs, VDIGINX = 7V (Mode 1) VDIGINX = 0V (Note 3) (Mode 1) VDIGINX = 0V (Note 4)
7.0 7.0 0.4 30 30 0.25 300 300 300
0.15 30 30 30
Charge Monitor A V 0.8 1 1 1 2 6 V A A A
Digital Inputs 2
3
LTC1479
AC ELECTRICAL CHARACTERISTICS
VDCIN = 25V, VBAT1 = 16V, VBAT2 = 12V, TA = 25C unless otherwise noted. (Note 2)
SYMBOL tONGA/GB tONGC/GD tONGE/GF tOFFGA/GB tOFFGC/GD tOFFGE/GF tONGG/GH tOFFGG/GH fOVGG tdLOBAT tdDCINGOOD PARAMETER Gate A/B Turn-On Time Gate C/D Turn-On Time Gate E/F Turn-On Time Gate A/B Turn-Off Time Gate C/D Turn-Off Time Gate E/F Turn-Off Time Gate G/H Turn-On Time Gate G/H Turn-Off Time VGG Reg Operating Frequency LOBAT Delay Times DCINGOOD Delay Times CONDITIONS VGS > 3V (Note 5) VGS > 3V (Note 5) VGS > 3V (Note 5) VGS < 1V (Note 5) VGS < 1V (Note 5) VGS < 1V (Note 5) VGS > 3V (Note 5) VGS < 1V (Note 5) VBDIV = 100mV, RPULLUP = 51k VDCDIV = 100mV, RPULLUP = 51k MIN TYP 30 30 30 3 3 3 300 5 30 5 5 MAX UNITS s s s s s s s s kHz s s
The q denotes specifications which apply over the full operating temperature range. Note 1: The logic inputs are high impedance CMOS gates with ESD protection diodes to ground and therefore should not be forced below ground. These inputs can however be driven above the VCCP or VCC supply rails as there are no clamping diodes connected between the input pins and the supply rails. This facilitates operation in mixed 5V/3V systems. Note 2: The Selected Operating Mode Truth Table, which defines the operating conditions and logical states associated with each "normal" operating mode, should be used in conjunction with the Electrical
Characteristics table to establish test conditions. Actual production test conditions may be more stringent. Note 3: The following inputs are high impedance CMOS inputs: 3DM and DCIN/BAT and have no internal pull-up current. Note 4: The following inputs have built-in 2A pull-up current sources (passed through series diodes): BATSEL, BATDIS and CHGSEL. Note 5: Gate turn-on and turn-off times are measured with no inrush current limiting, i. e., VSENSE = 0V, using Si4936DY MOSFETs in the typical application circuit.
TRUTH TABLE
SELECTED MODES
(Selected Operating Modes)
LOGIC INPUTS SWITCH STATUS SW SW SW C/D E/F G Off Off Off Off Off On Off Off Off On Off Off Off Off Off Off Off Off Off Off OUTPUTS SW H Off Off Off On Off Off Off Off Off Off Off CHGMON Hi-Z BAT1 Hi-Z BAT2 Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z VBAT LOBAT BAT1 H BAT1 H BAT2 BAT2 BAT1 BAT2 BAT1 BAT1 BAT2 BAT1 BAT1 H H H H L L L L L DCINGOOD H H H H L L L L L H H
SW NO. MODE 3DM DCIN/BAT BATSEL BATDIS CHGSEL A/B 1 DC Operation H H H L H On 2 DC Operation and H H H H H On BAT1 Charging 3 DC Operation and H H L L L On Off BAT2 Disconnected 4 DC Operation and H H L H L On Off BAT2 Charging 5 BAT1 Operation H L H H H Off On 6 BAT2 Operation H L L H H Off Off 7 BAT1 Low and H L H L H Off Off Disconnected 8 Backup Operation H L H L H Off Off 9 No Power L L L L L Off Off (No Backup) 10 DC Reconnected L L H L H 3DM* 3DM* 11 DC Connected H H H L H On Off and Reset * 3DM = Three Diode Mode. When this mode is invoked, only the first MOSFET switch in each back-to-back switch pair, i. e., SW A, SW C and SW E is turned on. Current may still pass through the inherent body diode of the idled switches, i.e., SW B, SW D and SW F to help restart
3DM* Off Off Off
the system after abnormal operating conditions have been encountered. See the Timing Diagram and Applications Information sections for further details.
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LTC1479 TYPICAL PERFORMANCE CHARACTERISTICS
DCIN Supply Current
350 300
DCIN SUPPLY CURRENT (A)
BAT1 SUPPLY CURRENT (A)
250 200 150 100 50 0 0 5 20 30 15 25 10 DCIN SUPPLY VOLTAGE (V) 35
250 200 150 100 50 0 0 5 20 30 15 25 10 BAT1 SUPPLY VOLTAGE (V) 35
BAT2 SUPPLY CURRENT (A)
MODE 1, DCDIV = 1.5V NO OTHER POWER TJ = 25C
VBKUP Supply Current
70 60 50 40 30 20 10 0 0 5 20 30 15 25 VBKUP SUPPLY VOLTAGE (V) 10 35 MODE 8 NO OTHER POWER TJ = 25C
VBKUP SUPPLY CURRENT (A)
VGG SUPPLY VOLTAGE (V)
VCC Supply Voltage
4.0 3.9
VCC SUPPLY VOLTAGE (V)
MODE 1 VDCIN = 24V
3.8 3.7 3.6 3.5 3.4 3.3 50 100 25 75 - 50 - 25 0 JUNCTION TEMPERATURE (C)
VCCP SUPPLY VOLTAGE (V)
UW
1479 G01
BAT1 Supply Current
350 300 MODE 5 NO OTHER POWER TJ = 25C 350 300 250 200 150 100 50 0
BAT2 Supply Current
MODE 6 NO OTHER POWER TJ = 25C
0
5
20 30 15 25 10 BAT2 SUPPLY VOLTAGE (V)
35
1479 G02
1479 G03
VGG Supply Voltage
44 42 40 38 36 34 32 30 50 100 25 75 - 50 - 25 0 JUNCTION TEMPERATURE (C) MODE 1 VDCIN = 24V
125
1479 G04
1479 G05
VCCP Supply Voltage
6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 50 100 25 75 - 50 - 25 0 JUNCTION TEMPERATURE (C) MODE 1 VDCIN = 24V
125
125
1479 G06
1479 G07
5
LTC1479
PIN FUNCTIONS
External Power Supply Pins DCIN (Pin 1): Supply Input. A 330 resistor should be put in series with this pin and the external DC power source. A 0.1F bypass capacitor should be connected to this pin as close as possible. DCDIV (Pin 2): Supply Divider Input. This is a high impedance comparator input with a 1.215V threshold (rising edge) and approximately - 35mV hysteresis. BAT1, BAT2 (Pins 35, 34): Supply Input. These two pins are the inputs from the two batteries. A 1F bypass capacitor should be connected to each pin as close as possible if there is no larger battery supply capacitor within 2". VBAT (Pin 32): Battery Voltage Sense. This pin connects the top of the battery resistor ladder to either BAT1 or BAT2. BDIV (Pin 33): Battery Divider Input. A high impedance comparator input with a 1.215V threshold (falling edge) and approximately 35mV hysteresis. VBKUP (Pin 36): Supply Input. This input supplies power to the LTC1479 when in the backup mode of operation. A 1F bypass capacitor should be connected to the VBKUP pin as close as possible if there is no larger backup supply capacitor within 2". Internal Power Supply Pins VCCP (Pin 20): Power Supply Output. Bypass this output with at least a 0.1F capacitor. The VCCP power supply is used primarily to power internal logic circuitry. VCC (Pin 15): Power Supply Output. This is a nominal 3.60V output. Bypass this regulator output with a 2.2F tantalum capacitor. This capacitor is required for stability. V + (Pin 17): Supply. The V + pin is connected via three internal diodes to the DCIN, BAT1 and BAT2 pins and powers the top of the VGG switching regulator inductor. Bypass this pin with a 1F/35V capacitor. VGG (Pin 16): Gate Supply. This high voltage (36.5V) switching regulator is intended only for driving the internal micropower gate drive circuitry. Do not load this pin with any external circuitry. Bypass this pin with a 1F/50V capacitor. SW (Pin 18): Output. This pin drives the "bottom" of the VGG switching regulator inductor which is connected between this pin and the V + pin. GND (Pin 19): Ground. The VGG and V + bypass capacitors should be returned to this ground which is connected directly to the source of the N-channel switch in the VGG regulator. Input Power Switches GA, GB (Pins 4, 6): DCIN Switch Gate Drive. These two pins drive the gates of the back-to-back N-channel switches in series with the DCIN input. SAB (Pin 5): Source Return. The SAB pin is connected to the sources of SW A and SW B. A small pull-down current source returns this node to 0V when the switches are turned off. GC, GD (Pins 7, 9): BAT1 Switch Gate Drive. These two pins drive the gates of the back-to-back N-channel switches in series with the BAT1 input. SCD (Pin 8): Source Return. The SCD pin is connected to the sources of SW C and SW D. A small pull-down current source returns this node to 0V when the switches are turned off. GE, GF (Pins 10, 12): BAT2 Switch Gate Drive. These two pins drive the gates of the back-to-back N-channel switches in series with the BAT2 input. SEF (Pin 11): Source Return. The SEF pin is connected to the sources of SW E and SW F. A small pull-down current source returns this node to 0V potential when the switches are turned off. SENSE + (Pin 13): Inrush Current Input. This pin should be connected directly to the "top" (switch side) of the low valued resistor in series with the three input power selector switch pairs, SW A/B, SW C/D and SW E/F, for detecting and controlling the inrush current into and out of the power supply sources and the output capacitor.
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LTC1479
PIN FUNCTIONS
SENSE - (Pin 14): Inrush Current Input. This pin should be connected directly to the "bottom" (output side) of the low valued resistor in series with the three input power selector switch pairs, SW A/B, SW C/D and SW E/F, for detecting and controlling the inrush current into and out of the power supply sources and the output capacitor. Battery Charging Switches GG, GH (Pins 29, 27): Charger Switch Gate Drive. These two pins drive the gates of the back-to-back N-channel switch pairs, SW G and SW H, between the charger output and the two batteries. SG, SH (Pin 28, 26): Source Returns. These two pins are connected to the sources of SW G and SW H respectively. A small pull-down current source returns these nodes to 0V when the switches are turned off. CHGMON (Pin 31): Battery Selector Output. This pin is the output of an internal switch which is connected to BAT1 and BAT2 and connects the positive terminal of the selected battery to the voltage feedback resistors in the charger circuit. Microprocessor Interface DCINGOOD (Pin 25): Comparator Output. This open-drain output has an internal 2A pull-up current source connected through a diode to the VCCP power supply. An external pull-up resistor can be added if more pull-up current is required. This output is active high when the DC supply rises above the programmed voltage. LOBAT (Pin 3): Comparator Output. This open-drain output does not have an internal pull-up current source and is active low when the selected battery voltage drops below the programmed voltage. DCIN/BAT (Pin 24): Selector Input. This high impedance logic input allows the P to make the ultimate decision on the connection of the DC power source, based upon the DCINGOOD pin information. In some minimized systems, the DCIN/BAT pin may be connected directly to the DCINGOOD pin. BATDIS (Pin 23): Battery Disconnect Input. This highimpedance logic input has a built-in 2A pull-up current source and allows the P to disconnect the battery from the system. 3DM (Pin 22): Three Diode Mode Input. This high impedance logic input has no built-in pull-up current source. Connect a 100k resistor from this pin to ground to ensure three diode mode operation from a "cold start." CHGSEL (Pin 21): Battery Charger Selector Input. This high impedance logic input has a built-in 2A pull-up current source and allows the P to determine which battery is being charged by connecting the selected battery to the charger output via one of the switch pairs, SW G or SW H. (The charger voltage feedback ladder is simultaneously switched to the selected battery.) BATSEL (Pin 30): Battery Selector Input. This high impedance logic input has a built-in 2A pull-up current source and allows the P to select which battery is connected to the system and the battery monitor comparator input. Battery 1 is selected with a logic high on this input and battery 2 is selected with a logic low.
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LTC1479
BLOCK DIAGRAM
DCIN
DCDIV
DCIN MONITOR SW A/B GATE DRIVERS BAT1 BAT2 DCIN SW C/D GATE DRIVERS SW E/F GATE DRIVERS
V+ VCC REGULATOR & BIAS GENERATOR VCCP 2A SWITCH CONTROL LOGIC VGG SWITCHING REGULATOR
VCC VGG
SW
VCCP 2A
VCCP BAT2
BAT1
BATSEL
VBAT
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GA SAB GB GC SCD GD GE SEF GF VSENSE + VSENSE - BAT2 INRUSH SENSE BAT1 INRUSH SENSE DCIN INRUSH SENSE VCCP 2A VCCP 2A VCCP 3DM BATDIS DCIN/BAT DCINGOOD BAT1 BAT2 DCIN VBKUP LOBAT BATTERY MONITOR SW G GATE DRIVER SW H GATE DRIVER GND CHGSEL CHGMON BDIV SG GG SH GH
1479 BD
LTC1479
TI I G DIAGRA S
DC and Battery Operation Timing
MODE 1 DC OPERATION BAT1 DISCONNECTED 25V DCIN 0V 25V OUTPUT 0V DCINGOOD DCIN/BAT BATDIS BATSEL CHGSEL (16V) (12V) MODE 2 DC OPERATION BAT1 CHARGING MODE 3 DC OPERATION BAT2 DISCONNECTED MODE 4 DC OPERATION BAT2 CHARGING
NOTE: FOR MODES 1 TO 6, 3DM = H, BAT1 = 16V, BAT2 = 12V
MODE 7 BAT1 LOW & DISCONNECTED 25V DCIN 0V
25V OUTPUT 0V LOBAT BATDIS DCIN/BAT 3DM
BAT1 DISCHARGING (VBKUP = 6V) (0V)
NOTE: FOR MODES 7 TO 12, BATSEL = H, BAT1 = 16V AND DISCHARGING, BAT2 = 0V
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MODE 5 BAT1 OPERATION
MODE 6 BAT2 OPERATION
1479 TD01
Backup and DC Restoration Timing
MODE 8 BACKUP OPERATION
MODE 9 NO POWER (NO BACKUP)
MODE 10 DC RESTORED (THREE DIODE MODE)
MODE 11 DC RECONNECTED (SW A/B ON)
MODE 12 THREE DIODE MODE
(25V) (24.3V) (24.3V)
1479 TD02
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LTC1479
OPERATION
The LTC1479 is responsible for low-loss switching at the "front end" of the power management system, where up to two battery packs and a DC power source can be indiscriminately connected and disconnected. Smooth switching between input power sources is accomplished with the help of low-loss N-channel switches driven by special gate drive circuitry which limits the inrush current in and out of the battery packs and the system power supply capacitors. All N-Channel Switching The LTC1479 drives external back-to-back N-channel MOSFET switches to direct power from the three main power sources: the external DC power source, the primary battery and the secondary battery connected to the main supply pins--DCIN, BAT1 and BAT2 respectively. (N-channel MOSFET switches are more cost effective and provide lower voltage drops than their P-channel counterparts.) Gate Drive (VGG) Power Supply The gate drive for the low-loss N-channel switches is supplied by a micropower boost regulator which is regulated at approximately 36.5V. The VGG supply provides sufficient headroom above the maximum 28V operating voltage of the three main power sources to ensure that the MOSFET switches are fully enhanced. The power for this inductor based regulator is taken from three internal diodes as shown in Figure 1. The three
DCIN BAT1 BAT2 LTC1479 V+ L1 1mH LTC1479 DCIN
TO GATE DRIVERS
VGG SWITCHING REGULATOR
Figure 1. VGG Switching Regulator
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diodes are connected to each of the three main power sources, DCIN, BAT1 and BAT2. The highest voltage potential is directed to the top of the boost regulator inductor to maximize regulator efficiency. C1 provides filtering at the top of the 1mH switched inductor, L1, which is housed in a small surface mount package. A fourth internal diode directs the current from the 1mH inductor to the VGG output capacitor, C2, further reducing the external parts count. In fact, as demonstrated in Figure 1, only three external components are required by the VGG regulator, L1, C1 and C2. Inrush Current Limiting The LTC1479 uses an adaptive inrush current limiting scheme to reduce current flowing in and out of the three main power sources and the DC/DC converter input capacitor during switch-over transitions. The voltage across a single small-valued resistor, RSENSE, is measured to ascertain the instantaneous current flowing through the three main switch pairs, SW A/B, SW C/D, and SW E/F during the transitions. Figure 2 is a block diagram showing only the DCIN switch pair, SW A/B. (The gate drive circuits for switch pairs SW C/D and SW E/F are identical). A bidirectional current sensing and limiting circuit determines when the voltage drop across RSENSE reaches plus or minus 200mV. The gate-to-source voltage, VGS, of the appropriate switch is limited during the transition period until the inrush current subsides, generally within a few milliseconds, depending upon the value of the DC/DC converter input capacitor.
SW A SW B RSENSE OUTPUT TO DC/DC CONVERTER COUT
+
GA 6V SAB 6V 200mV THRESHOLD GB VSENSE + VSENSE -
(36.5V)
VGG SW
+
C2 1F 50V
+
C1 1F 35V SW A/B GATE DRIVERS
VGG GND
1479 F01
BIDIRECTIONAL INRUSH CURRENT SENSING AND LIMITING
1479 F02
Figure 2. SW A/B Inrush Current Limiting
LTC1479
OPERATION
This scheme allows capacitors and MOSFET switches of differing sizes and current ratings to be used in the same system without circuit modifications. After the transition period has passed, the VGS of both MOSFETs in the selected switch pair rises to approximately 6V. The gate drive is set at 6V to provide ample overdrive for logic level MOSFET switches without exceeding their maximum VGS rating. Internal Power Supplies Two internal supplies provide power for the control logic and power source monitoring functions. The VCCP logic supply is approximately 5V and provides power for the majority of the internal logic circuitry. The VCC supply is approximately 3.60V and provides power for the VGG switching regulator control circuitry and the gate drivers. The VCC supply has an undervoltage lockout circuit which minimizes power consumption in the event of a total loss of system power; i.e., when all available power sources fall below approximately 4.5V. DCIN Voltage Monitoring The DCIN input is continuously monitored via a two resistor ladder connected between the DCIN pin and the DCDIV input. The input threshold is 1.215V (rising edge) with approximately - 35mV hysteresis. The use of a definitive voltage threshold ensures that the DC supply is not only connected but "healthy" before being attached to the DC/DC converter input. Battery Voltage Monitoring The LTC1479 has the ability to independently monitor both battery packs. (Because of this, one battery pack may be discharged as the other is being charged.) A low-battery detector signals when the selected battery pack has dropped to the level where a shutdown sequence should be initiated or the other battery pack engaged. Battery Charging Management Functions The LTC1479 directly interfaces with LT1510/LT1511 battery charger circuits. Two gate drive circuits control the two back-to-back N-channel switch pairs, SW G and SW H, under logic (CHGSEL) control to connect the output of the charger to the selected battery pack. Breakbefore-make action ensures that current does not pass from one battery pack to the other during switch-over of the charger output. The CHGSEL input also simultaneously switches the positive terminal of the selected battery pack to the top of the voltage feedback resistor ladder in the charger system through the CHGMON pin. Backup Supply Interface Power for the LTC1479 is obtained from the backup supply when power is unavailable from the three main sources of power. Interface to Companion Microprocessor A companion P must be used in conjunction with the LTC1479 to provide overall control of the power management system. The LTC1479 communicates with the P by means of five logic inputs and two logic outputs as described in Table 1.
Table 1. LTC1479 P Interface Inputs and Outputs
INPUT DCIN/BAT BATDIS BATSEL CHGSEL 3DM OUTPUT DCINGOOD LOBAT ACTION Logic High Required to Connect a Good DC Supply Logic Low Disconnects the Battery from the System Selects Which Battery is Connected to the System (Logic High Selects BAT1; Logic Low Selects BAT2) Selects Which Battery is Charged and Monitored (Logic High Selects BAT1; Logic Low Selects BAT2) Forces the Main Three Power Path Switches Into "3-Diode Mode." See Applications Information Section ACTION Logic High When a Good DC Supply is Present Logic Low When Selected Battery Voltage is Low
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LTC1479
APPLICATIONS INFORMATION
POWER PATH SWITCHING CONCEPTS Power Source Selection The LTC1479 drives low-loss switches to direct power in the main power path of a dual rechargeable battery system -- the type found in most notebook computers and other portable equipment. Figure 3 is a conceptual block diagram which illustrates the main features of an LTC1479 dual battery power management system, starting with the three main power sources and ending at the system DC/DC regulator. Switches SW A/B, SW C/D and SW E/F direct power from either the AC adapter (DCIN) or one of the two battery packs (BAT1 and BAT2) to the input of the DC/DC switching regulator. Switches SW G and SW H connect the desired battery pack to the battery charger. Each of the five switches is intelligently controlled by the LTC1479 which interfaces directly with a power management system P. Using Tantalum Capacitors The inrush and "outrush" current of the system DC/DC regulator input capacitor is limited by the LTC1479. i.e., the current flowing both in and out of the capacitor during transitions from one input power source to another is limited. In many applications, this inrush current limiting makes it feasible to use lower cost/size tantalum surface mount capacitors in place of more expensive/larger aluminum electrolytics at the input of the DC/DC converter.
SW A/B DCIN SW C/D BAT1 SW E/F BAT2 SW G BATTERY CHARGER LTC1479 PowerPath CONTROLLER POWER MANAGEMENT P SW H CIN RSENSE 12V
Figure 3. LTC1479 PowerPath Conceptual Diagram
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Note: The capacitor manufacturer should be consulted for specific inrush current specifications and limitations and some experimentation may be required to ensure compliance with these limitations under all possible operating conditions.
Back-to-Back Switch Topology The simple SPST switches shown in Figure 3 actually consist of two back-to-back N-channel switches. These low-loss, N-channel switch pairs are housed in 8-pin SO and SSOP packaging and are available from a number of manufacturers. The back-to-back topology eliminates the problems associated with the inherent body diodes in power MOSFET switches and allows each switch pair to block current flow in either direction when the two switches are turned off. The back-to-back topology also allows for independent control of each half of the switch pair which facilitates bidirectional inrush current limiting and the so called "3diode" mode described in the following section. The "3-Diode" Mode Under normal operating conditions, both halves of each switch pair are turned on and off simultaneously. For example, when the input power source is switched from a good DC input (AC adapter) to a good battery pack, BAT1, both gates of switch pair SW A/B are turned off and both gates of switch pair SW C/D are turned on. The back-toback body diodes in switch pair, SW A/B, block current flow in or out of the DC input connector.
+
HIGH EFFICIENCY DC/DC SWITCHING REGULATOR
5V
3.3V
1479 F03
LTC1479
APPLICATIONS INFORMATION
In the "3-diode" mode, only the first half of each power path switch pair, i.e., SW A, SW C and SW E, is turned on; and the second half, i.e., SW B, SW D and SW F, is turned off. These three switch pairs now act simply as three diodes connected to the three main input power sources as illustrated in Figure 4. The power `diode' with the highest input voltage passes current through to the input of the DC/DC converter to ensure that the power management P is powered at start-up or under abnormal operating conditions. (An undervoltage lockout circuit defeats this mode when the V + pin drops below approximately 4.5V). "Cold Start" Initial Condition The LTC1479 is designed to start in the "3- diode" mode when all five logic inputs are low-- when no power is available (including the backup system). A 100k resistor from the 3DM input to ground ensures that this input is low during a "cold start." This will cause the main PowerPath switches to pass the highest voltage available to the input of the DC/DC converter. Normal operation will then resume after a good power source is identified. Recovery from Uncertain Power Conditions The "3-diode" mode can also be asserted (by applying an active low to the 3DM input) when abnormal conditions exist in the system, i.e., when all power sources are deemed not "good" or are depleted, or the management system P is being reset or not functioning properly. (See
SW B SW A DCIN SW D ON BAT1 SW F ON BAT2 ON OFF OFF SW E CIN OFF SW C RSENSE 12V
LTC1479 PowerPath CONTROLLER
Figure 4. LTC1479 PowerPath Switches in "3-Diode" Mode
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the Power Management P Interface section for additional information on when to invoke "3-diode" mode.) COMPONENT SELECTION N-Channel Switches The LTC1479 adaptive inrush limiting circuitry permits the use of a wide range of logic-level N-channel MOSFET switches. A number of dual low RDS(ON) N-channel switches in 8-lead surface mount packages are available that are well suited for LTC1479 applications. The maximum allowable drain source voltage, VDS(MAX), of the three main switch pairs, SW A/B, SW C/D and SW E/F, must be high enough to withstand the maximum DC supply voltage. If the DC supply is in the 20V to 28V range, use 30V MOSFET switches. If the DC supply is in the 10V to 18V range, and is well regulated, then use 20V MOSFET switches. As a general rule, select the switch with the lowest RDS(ON) at the maximum allowable VDS. This will minimize the heat dissipated in the switches while increasing the overall system efficiency. Higher switch resistances can be tolerated in some systems with lower current requirements, but care should be taken to ensure that the power dissipated in the switches is never allowed to rise above the manufacturer's recommended levels. The maximum allowable drain-source voltage, VDS(MAX), of the two charger switch pairs, SW G and SW H, need only
+
HIGH EFFICIENCY DC/DC SWITCHING REGULATOR 5V
3.3V
POWER MANAGEMENT P
1479 F04
13
LTC1479
APPLICATIONS INFORMATION
be high enough to withstand the maximum battery or charger output voltage. In most cases, this will allow the use of 20V MOSFET switches in the charger path, while 30V switches are used in the main power path. Inrush Current Sense Resistor, RSENSE A small valued sense resistor (current shunt) is used by the three main switch pair drivers to measure and limit the inrush current flowing through the conducting switch pair.
DC SUPPLY LTC1479 DCIN RDC2 1% DCDIV RDC1 12.1k 1% 1.215V DCINGOOD TO SW A/B
It should be noted that the inrush limiting circuit is not intended to provide short-circuit protection ; but rather, is designed to limit the large peak currents which flow into or out of the large power supply capacitors and the battery packs during power supply switch-over transitions. The inrush current limit should be set at approximately 2x or 3x the maximum required DC/DC input current.
For example, if the maximum current required by the DC/DC converter is 2A, an inrush current limit of 6A is set by selecting a 0.033 sense resistor, RSENSE, using the following formula: RSENSE = (200mV)/IINRUSH Note that the voltage drop across the resistor in this example is only 66mV under normal operating conditions. Therefore, the power dissipated in the resistor is extremely small (132mW), and a small 1/4W surface mount resistor can be used in this application. A number of small valued, surface mount resistors are available that have been specifically designed for high efficiency current sensing applications. DC Input Monitor Resistor Divider The DCDIV input continuously monitors the DC power supply voltage via a two resistor divider network, RDC1 and RDC2, as shown in Figure 5. The threshold voltage of the DC good comparator is 1.215V when the power supply input voltage is rising. Approximately - 35mV of hysteresis is provided to ensure clean switching of the comparator when the DC supply voltage is falling. To minimize errors due to the input bias current of the DC good comparator, set RDC1 = 12.1k so that approximately 100A flows through the resistor divider when the desired
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+ -
1479 F05
Figure 5. DC Monitor Resistor Divider
BATSEL BAT1 BAT2 VBAT LOBAT SWITCH CONTROL LOGIC
RB2 1% BDIV RB1 121k 1%
1.215V
+ -
LTC1479
1479 F06
Figure 6. Battery Monitor Resistor Divider
threshold is reached. RDC2 is then selected according to the following formula: RDC2 = 12.1k
)
VGOOD -1 1.215V
)
Battery Monitor Resistor Divider A switch controlled by the BATSEL input connects one of the two batteries to the VBAT pin and therefore to the top of the battery resistor divider as shown in Figure 6. The threshold voltage of the low-battery comparator is 1.215V when the battery voltage is falling. Approximately +35mV of hysteresis is provided to ensure clean switching of the comparator when the battery voltage rises again. To minimize errors due to the input bias current of the low battery comparator, assume RB1 = 121k so that approximately 10A flows through the resistor divider when the threshold is reached. RB2 is selected according to the following formula:
LTC1479
APPLICATIONS INFORMATION
V RB2 = 121k LOBAT - 1 1.215V
)
)
VGG Regulator Inductor and Capacitors The VGG regulator provides a power supply voltage significantly higher than any of the three main power source voltages to allow the control of N-channel MOSFET switches. This 36.5V micropower, step-up voltage regulator is powered by the highest potential available from the three main power sources for maximum regulator efficiency. Because the three input supply diodes and regulator output diode are built into the LTC1479, only three external components are required by the VGG regulator: L1, C1 and C2 as shown in Figure 7. L1 is a small, low current 1mH surface mount inductor. C1 provides filtering at the top of the 1mH switched inductor and should be 1F to filter switching transients. The VGG output capacitor, C2, provides storage and filtering for the VGG output and should be 1F and rated for 50V operation. C1 and C2 can be either tantalum or ceramic capacitors. VCC and VCCP Regulator Capacitors The VCCP logic supply is approximately 5V and provides power for the majority of the internal logic circuitry. Bypass this output with a 0.1F capacitor.
DCIN BAT1 BAT2 LTC1479 V+ L1* 1mH
TO GATE DRIVERS
(36.5V)
VGG SW
+
VGG SWITCHING REGULATOR
C2 1F 50V
GND
1479 F07
*COILCRAFT 1812LS-105 XKBC (708) 639-6400 OR EQUIVALENT
Figure 7. VGG Step-Up Switch Regulator
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The VCC supply is approximately 3.60V and provides power for the VGG switching regulator control circuitry and the gate drivers. Bypass this output with a 2.2F tantalum capacitor. This capacitor is required for stability of the VCC regulator output. SYSTEM LEVEL CONSIDERATIONS The Complete Power Management System The LTC1479 is the "heart" of a complete power management system and is responsible for the main power path and charger switching. A companion power management P provides overall control of the power management system in concert with the LTC1479 and the auxiliary power management systems. A typical dual Li-Ion battery power management system is illustrated in Figure 8. If "good" power is available at the DCIN input (from the AC adapter), switch pair SW A/B are turned on--providing a low-loss path for current flow to the input of the LTC1538-AUX DC/DC converter. Switch pairs, SW C/D and SW E/F are turned off to block current from flowing back into the two battery packs from the DC input. In this case, an LT1510 constant-voltage/constant-current (CC/CV) battery charger circuit is used to alternately charge the two Li-Ion battery packs. The P "decides" which battery is in need of recharging by either querying the "smart" battery directly or by more indirect means. After the determination is made, either switch pair, SW G or SW H, is turned on to pass charger output current to one of the batteries. Simultaneously, the selected battery voltage is returned to the voltage feedback input of the LT1510 CV/CC battery charger via the CHGMON output of the LTC1479. After the first battery has been charged, it is disconnected from the charger circuit and the second battery is connected through the other switch pair and the second battery charged. Backup power is provided by the LT1304 circuit which ensures that the DC/DC input voltage does not drop below 6V. Backup System Interface The LTC1479 is designed to work in concert with related power management products including the LT1304 mi-
C1 1F 35V
15
LTC1479
APPLICATIONS INFORMATION
DCIN SW A SW B SW C SW D SW E 330 RDC2 Li-ION BATTERY PACK #1 0.1F BACKUP NiCD GA SAB GB GC SCD GD GE SEF GF SENSE + SENSE - BACKUP REGULATOR SW F RSENSE 0.033 12V AUX LTC1538-AUX TRIPLE, HIGH EFFICIENCY, SWITCHING REGULATOR 5V 3.3V
DCIN DCDIV
RDC1
BAT1 BAT2 Li-ION BATTERY PACK #2 VBAT RB2 BDIV RB1 CHGMON VCC 2.2F 16V VCCP V+
1mH*
+
0.1F
+
1F 50V
+
*COILCRAFT 1812LS-105 XKBC (708) 639-1469
Figure 8. Simplified Dual Li-Ion Battery Power Management System
FROM PowerPath CONTROLLER 5VCC FROM DC/DC
(BOLD LINES INDICATE HIGH CURRENT PATHS) ROHM DTA144E R1 10k NiCD CELL L1* 10H D1 MBR0530
+
C1 0.1F R4 390k 1% 4 SW R5 100k 1%
BACKUP Q1 2N7002 D2 BAS16LT1
2 1
LBO LT1304 LBI ILIM GND 5 6 R3 22k
FB SHDN VIN
8 7 3
R2 470k
5VCC FROM DC/DC C3 0.1F
1479 F09
C2 0.1F
Figure 9. LT1304 Micropower Backup Converter Circuit
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VBKUP
LTC1479
2 POWER MANAGEMENT P
5
SW VGG
GG SG
GH SH DCIN
1F 50V
+
SW H SW G
1479 F08
LT1510 Li-ION BATTERY CHARGER
TO INPUT OF DC/DC CONVERTER
cropower DC/DC converter. As shown in Figure 9, the LT1304 monitors the input supply voltage and activates when it drops below 6V. Power for the DCIN and battery monitors and the logic supply in the LTC1479 is then obtained from the output of the LT1304 step-up regulator. Charger System Interface The LTC1479 is designed to work directly with constantvoltage (CV), constant-current (CC) battery chargers such as the LT1510 and LT1511. LT1510 Battery Charger Interface As illustrated in Figure 10, the LT1510 CV/CC battery charger, takes power from the DC adapter input through Schottky diode D1. The output of the charger is directed to
LTC1479
APPLICATIONS INFORMATION
the charging battery through one of the N-channel switch pairs, SW G or SW H. The charging battery voltage is simultaneously connected through the CHGMON switch in the LTC1479 to the top of the charger voltage resistor divider, R4 and R5, for constant voltage charging. (See the LT1510 data sheet for further detail.)
POWER MANAGEMENT P TO SW C/D CHGMON LTC1479 BAT1 BAT2 GG SG GH SH DCIN 0.1F TO SW E/F TO SW A/B C6 10F CERAMIC D1 MBRS140T VCC SW PROG VC BOOST R2 300 C1 1F R3 1k C2 0.1F GND BAT LT1510 SENSE OVP R5 115k 0.25% C3 0.22F D3 1N4148 L1* 33H R4 649k 0.25% 330 DC INPUT (FROM AC ADAPTOR) D2 MBRS140T
+
BAT1 4 Li-ION BATTERY PACK
+C - +
BAT1
47F
SW G Si9926DY
BAT2 4 Li-ION BATTERY PACK
+ CBAT2 -
47F SW H Si9926DY
*COILTRONICS CTX33-2
CURRENT CONTROL FROM POWER MANAGEMENT P
Figure 10. Interfacing to the LT1510 Constant-Voltage/Constant-Current Battery Charger
POWER MANAGEMENT P
CHGMON LTC1479 BAT1 BAT2 GG SG GH SH DCIN
TO SW C/D TO SW E/F
+
BAT1 4 Li-ION BATTERY PACK
+ - +
CBAT1 47F
SW G Si9926DY
BAT2 4 Li-ION BATTERY PACK
+ -
CBAT2 47F
SW H Si9926DY
CURRENT CONTROL FROM POWER MANAGEMENT P
Figure 11. Interfacing to the LT1511 Constant-Voltage/Constant-Current Battery Charger with Input Current Limiting
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LT1511 Battery Charger Interface The LT1511, 3A CC/CV battery charger with input current limiting, is connected in a slightly different manner than the LT1510 as illustrated in Figure 11.
RPROG 11k 1% Q1 2N7002
R1 100k 1%
(CHARGER OUTPUT)
+
CCHG 22F TANT
1479 F10
330 C4 10F CERAMIC
RS4 0.05
D1 MBRS340T R3 500 R4 5k R5 6.8k
+
0.1F TO SW A/B
C5 10F
C12 1F
DC INPUT (FROM AC ADAPTOR)
CLN VCC CLP UV PROG SW VC R2 1k C2 0.33F COMP1 BOOST C3 200pF LT1511 SPIN GND BAT OVP SENSE RS3 200 1%
D2 MBRS340T C6 0.47F L1 20H D3 MBR0540T
RPROG 4.93k 1% C1 1F
R1 500
R6 649k 0.25% R7 115k 0.25%
1479 F11
Q1 2N7002 (CHARGER OUTPUT)
RS2 200 1%
C7 50pF
RS1 0.033 CCHG 22F TANT
+
17
LTC1479
APPLICATIONS INFORMATION
The LT1511 has a third control loop that regulates the current drawn from the AC adapter. Therefore, the DC input to the LTC1479 and the input to the host system through SW A/B, is obtained from the "output" of the LT1511 adapter sense resistor, RS4, and not directly from the DC input connector as with the LT1510. This allows simultaneous operation of the host system while charging a battery without overloading the AC adapter. Charging current is reduced to keep the adapter current within specified levels. However, as with the LT1510 , the output of the LT1511 is directed to the charging battery through either SW G or SW H, and the charging battery voltage is connected to the top of the voltage resistor divider, R6 and R7, for constant voltage charging. (See the LT1511 data sheet for further detail on battery charging techniques and applications hints.) LT1620/LTC1435 Battery Charger Interface The LTC1479 also interfaces with the LT1620/LTC1435 synchronous high efficiency low dropout battery charger. The circuit shown in Figure 12 is a constant-current/ constant-voltage battery charger specifically designed for lithium-ion applications having thermal, output current, or input voltage headroom constraints which preclude the use of other high performance chargers such as the LT1510 or LT1511. This circuit can charge batteries at up to 4A. The precision current sensing of the LT1620 combined with the high efficiency and low dropout characteristics of the LTC1435 provide a battery charger with over 96% efficiency requiring only 0.5V input-to-output differential at 3A charging current. Charge current programming is achieved by applying a 0A to 100A current from the LT1620 PROG pin to ground, which can be derived from a resistor or DAC output controlled by the power management P. (See the LT1620 data sheet for further details on this circuit.) Capacitive Loading on the CHGMON Output In most applications, there is virtually no capacitive loading on the CHGMON output--just a simple resistor divider. Care should be taken to restrict the amount of capacitance to ground on the CHGMON output to less than 100pF. If more capacitance is required, it may become necessary to "mask" the LOBAT output when the charge monitor is switched between batteries. (Internal resistance between the BAT1 and BAT2 inputs and the charge monitor switch may create a transient voltage drop at the VBAT output during transitions which could be falsely interpreted by the P as a low battery condition.) THE POWER MANAGEMENT MICROPROCESSOR Interfacing to the LTC1479 The LTC1479 can be thought as a "real world" interface to the power management P. It takes logic level commands directly from the P, and makes changes at high current and high voltage levels in the power path. Further, it provides information directly to the P on the status of the AC adapter, the batteries and the charging system. The LTC1479 logic inputs are TTL level compatible and therefore interface directly with standard power management Ps. Further, because of the direct interface via the five logic inputs and the two logic outputs, there is virtually no latency (i.e. time delay) between the P and the LTC1479. In this way, time critical decisions can be made by the P without the inherent delays associated with bus protocols, etc. These delays are acceptable in certain portions of the power management system, but it is vital that the power path switching control be made through a direct connection to the power management P. The remainder of the power management system can be easily interfaced to the P through a serial interface. Selecting a Power Management Microprocessor The power management P provides intelligence for the entire power system, is programmed to accommodate the custom requirements of each individual system and allow performance updates without resorting to costly hardware changes. The power management P must meet the requirements of the total power management system, including the LTC1479 controller, the batteries (and interface), the backup system, the charging system and the host processor. A number of inexpensive processors are available which can easily fulfill these requirements.
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LTC1479
APPLICATIONS INFORMATION
POWER MANAGEMENT P CHGMON LTC1479 BAT1 BAT2 GG SG GH SH DCIN 0.1F TO SW C/D TO SW E/F TO W A/B 330 DC INPUT (FROM AC ADAPTER)
+
BAT1 4 Li-ION BATTERY PACK
+ - +
CBAT1 10F
SW G Si9926DY
BAT2 4 Li-ION BATTERY PACK
+ -
CBAT2 10F
SW H Si9926DY
SHDN
C3 0.1F C4 0.033F
R5 1.5M COSC TG 2 RUN/SS BOOST 3 SW ITH LTC1435 4 VIN SFB 5 INTVCC SGND 6 VOSENSE BG C9, 100pF 7 SENSE - PGND C10 8 VCC SENSE + 100pF C6 0.1F C7 0.33F R3 10k 1% C8 0.1F 1 16 15 14 13 12 11 10 9 C13 D2* CMDSH-3 0.33F
C2 100pF
R5, 1k
1 2
SENSE IOUT
AVG
8
7 PROG LT1620 3 6 GND VCC 4 5 NIN PIN
IPROG
C5 0.01F
*CENTRAL SEMICONDUCTOR CO. (516) 435-1110
Figure 12. Interfacing to an LT1620/LTC1435 High Efficiency Constant-Voltage/Constant-Current Battery Charger
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C1 100pF R2 76.8k 0.1%
R1 1M 0.1%
C11 56pF C12 0.1F
+
Q1 Si4412DY L1 27H D1* CMDSH-3 Q2 Si4412DY
C15 22F 35V x2
R4 0.025
+
C16 22F 35V
C14 4.7F
+
1479 F12
19
LTC1479
APPLICATIONS INFORMATION
Interfacing to the Battery Pack The LTC1479 is designed to work with virtually any battery pack chemistry or cell count, as long as the battery pack operating voltage range is somewhere between 6V and 28V. This permits great flexibility in system design. The low-battery threshold is adjustable and can be set anywhere between 6V and 28V. Conventional Battery Packs Conventional battery packs do not include a "smart" battery interface between the battery pack and the host system. Thus, these battery packs generally have only three terminals to connect the battery and a temperature sensor (thermistor) to the host system. The NTC thermistor typically has a nominal resistance of 10k at room temperature and is used to monitor the battery pack temperature. LOBAT and DCINGOOD Blanking/Filtering It is good practice to include some delay in accepting low battery and DCIN good information during transitional periods, e.g., when switching the charger from one battery to another or when switching from batteries to DC power. This technique will eliminate false triggering at the associated P I/O. (Remember that the "3-diode" mode may be used during periods of uncertainty to eliminate the need for "instantaneous" DCIN and battery status information.) Smart Battery Packs Smart battery packs, compliant with the Smart Battery System specification, have a five-terminal connector. Two of the terminals are the minus and plus connections to the battery. A third terminal is connected to the top of a thermistor in NiCd and NiMH battery packs and to a resistor in Li-Ion battery packs. A fourth and fifth terminal are connected to the Smart Management Bus (SMBus) SMBDATA and SMBCLK lines from an integrated circuit inside the battery pack. Applications Assistance Linear Technology applications engineers have developed a smart battery charger around the LT1511 charger IC. Contact the factory for applications assistance in developing a complete smart battery system with intelligent PowerPath control using the LTC1479.
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LTC1479
TYPICAL APPLICATIONS N
Dual NiMH Battery Power Management System (Using an LT1510, 1A Charger)
Si4936DY SW A SW B 330 Si4936DY SW C SW D Si4936DY SW E SW F RSENSE 0.033
0.1F
RDC2 205k 1% RDC1 12.1k 1%
DCIN DCDIV
GA SAB GB
BAT1 BAT2 VBAT LTC1479 BDIV
RB2 909k 1% RB1 121k 1%
VCCP VCC GND V + SW C1 0.1F VGG L1* 1mH C2 2.2F 16V
+
+
C3 1F 50V
+
BAT1 12-CELL NiMH BATTERY PACK
+
RTH1
CBAT1 10F SW G Si9926DY RPROG 11k 1% Q1 2N7002
BAT2 12-CELL NiMH BATTERY PACK
+
RTH1
CBAT2 10F
SW H Si9926DY (CHARGER OUTPUT)
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(BOLD LINES INDICATE HIGH CURRENT PATHS) ROHM DTA144E R8 10k NiCD CELL D1 L2** 10H MBR0530
TO INPUT OF DC/DC CONVERTER
5VCC FROM DC/DC
+
C5 0.1F R2 390k 1%
GC SCD GD
GE SEF GF
SENSE +
SENSE - VBKUP Q2 2N7002 2 D5 BAS16LT1 4 8 LBO FB LT1304 7 SHDN 1 3 LBI VIN ILIM GND 6 R1 22k 5 C11 0.1F SW
R3 100k 1%
5VCC FROM DC/DC
R7 470k
C10 0.1F
BATSEL CHGSEL DCINGOOD 3DM GG SG GH SH BATDIS DCIN/BAT CHGMON LOBAT RCM2 909k 1% C4 1F 50V 100k
(BACKUP) VCC
POWER MANAGEMENT P
RCM1 100k 1%
SMBUS RTH1 RTH2 DC INPUT (FROM AC ADAPTOR)
D2 MBRS140T C6 10F CERAMIC 8 VCC SW 1 7 PROG 2 6 VC BOOST R6 1k C9 0.1F 3 LT1510 4
+
CDCIN 10F 35V ALUM D4 MBRS140T
C7 0.22F
R4 100k 1%
R5 300 C8 1F
D3 1N4148
L3*** 33H
GND
SENSE BAT 5
*1812LS-105 XKBC, COILCRAFT **CD43, SUMIDA ***CTX33-2, COILTRONICS
+
CCHG 22F TANT
1479 TA02
21
LTC1479
TYPICAL APPLICATIONS N
Dual Li-Ion Battery Power Management System
Si4936DY SW A SW B 330 Si4936DY SW C SW D Si4936DY SW E SW F RSENSE 0.033
0.1F
RDC2 205k 1% RDC1 12.1k 1%
DCIN DCDIV
GA SAB GB
BAT1 BAT2 VBAT LTC1479 BDIV
RB2 909k 1% RB1 121k 1%
VCCP VCC GND V + SW C1 0.1F VGG L1* 1mH C2 2.2F 16V
+
+
C3 1F 50V
+
BAT1 4 Li-ION SMART BATTERY PACK
+
RBAT1
CBAT1 10F SW G Si9926DY RPROG 3.83k 1% Q1 2N7002
BAT2 4 Li-ION SMART BATTERY PACK
+
RBAT2
CBAT2 10F
SW H Si9926DY (CHARGER OUTPUT)
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(BOLD LINES INDICATE HIGH CURRENT PATHS) ROHM DTA144E R8 10k NiCD + CELL D1 L2** 10H MBR0530 C5 0.1F
TO INPUT OF DC/DC CONVERTER
5VCC FROM DC/DC
GC SCD GD
GE SEF GF
SENSE +
SENSE - VBKUP Q2 2N7002 2 D5 BAS16LT1 4 8 LBO FB LT1304 7 SHDN 1 3 LBI VIN ILIM GND 6 R1 22k 5 C11 0.1F SW
R2 390k 1% R3 100k 1%
5VCC FROM DC/DC
R7 470k
C10 0.1F
BATSEL CHGSEL DCINGOOD 3DM GG SG GH SH BATDIS DCIN/BAT CHGMON LOBAT 100k
(BACKUP) VCC
C4 1F 50V RBAT1 RBAT2
POWER MANAGEMENT P
SMBUS
D2 MBRS140T C6 10F CERAMIC 14, 15 VCC SW 2 7 PROG 3 6 VC BOOST R6 1k C9 0.1F 1, 7-10, 16 LT1510 SENSE GND BAT 11 OVP 6 5
+
CDCIN 10F 35V ALUM
DC INPUT (FROM AC ADAPTOR) D4 MBRS140T
C7 0.22F D3 1N4148 L3*** 33H R7 649k 0.25% R8 115k 0.25%
R5 300 C8 1F
+
CCHG 22F TANT
*1812LS-105 XKBC, COILCRAFT **DT1608-223, COILCRAFT ***CTX33-2, COILTRONICS
1479 TA03
LTC1479
TYPICAL APPLICATIONS N
Dual Li-Ion Battery Power Management System (Using an LT1511, 3A Charger)
Si4936DY SW A SW B 330 Si4936DY SW C SW D Si4936DY SW E SW F RSENSE 0.033 (BOLD LINES INDICATE HIGH CURRENT PATHS) ROHM DTA144E R12 10k NiCD CELL D1 L2** 10H MBR0530 TO INPUT OF DC/DC CONVERTER
0.1F
RDC2 205k 1% RDC1 12.1k 1%
DCIN DCDIV
GA SAB GB
BAT1 BAT2 VBAT LTC1479 BDIV
RB2 1.05M 1% RB1 121k 1%
VCCP VCC GND V + SW C1 0.1F VGG L1* 1mH C2 2.2F 16V
+
+
C3 1F 50V
+
BAT1 4 Li-ION SMART BATTERY PACK
+
RBAT1
CBAT1 10F SW G Si9926DY RPROG 4.93k 1% C8 1F
BAT2 4 Li-ION SMART BATTERY PACK
+
RBAT2
CBAT2 10F
SW H Si9926DY
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
5VCC FROM DC/DC
+
C5 0.1F R2 390k 1%
GC SCD GD
GE SEF GF
SENSE +
SENSE - VBKUP Q2 2N7002 2 D5 BAS16LT1 4 SW LBO FB LT1304 7 SHDN 1 3 LBI VIN ILIM GND 6 R1 22k 5 C15 0.1F 8
R3 100k 1%
5VCC FROM DC/DC
R11 470k
C14 0.1F
BATSEL CHGSEL DCINGOOD 3DM GG SG GH SH BATDIS DCIN/BAT CHGMON LOBAT 100k
(BACKUP) VCC
C4 1F 50V RBAT1 RBAT2
POWER MANAGEMENT P
SMBUS
RS4 0.05 C6 10F CERAMIC
D1 MBRS340T R4 500 R10 5k R9 6.8k
+
C7 10F
C12 1F
+
CDCIN 10F 35V ALUM
DC INPUT (FROM AC ADAPTOR)
20 TO 22 10 9 19 CLN VCC CLP 6 UV PROG 18 2 SW VC R6 3 11 COMP1 BOOST 1k R5 C10 500 200pF LT1511 18 C9 SPIN 1, 4, 5, 7, 0.33F 16, 23, 24 8 GND OVP BAT SENSE RS2 200 1% (CHARGER OUTPUT) 14 12 RS1 0.033 CCHG 22F TANT RS3 200 1%
D2 MBRS340T C13 0.47F D3 MBR0540T L3*** 20H R7 649k 0.25% R8 115k 0.25%
Q1 2N7002
C11 50pF
+
*1812LS-105 XKBC, COILCRAFT **DT1608-223, COILCRAFT ***CTX20-4, COILTRONICS
1479 TA04
23
LTC1479
PACKAGE DESCRIPTION
0.205 - 0.212** (5.20 - 5.38)
0.005 - 0.009 (0.13 - 0.22)
0.022 - 0.037 (0.55 - 0.95)
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
RELATED PARTS
PART NUMBER
LT1304 LTC1435 LTC1438 LTC1473 LT1510 LT1511 LTC1538-AUX LT1620 LT1621
DESCRIPTION
Micropower DC/DC Step-Up Converter High Efficiency Synchronous Step-Down Converter Dual High Efficiency Synchronous Step-Down Converter Dual PowerPath Switch Driver Constant-Voltage/Constant-Current Battery Charger Constant-Voltage/Constant-Current 3A Battery Charger Dual, Synchronous Controller with Aux Regulator Battery Charger Current Controller Dual Battery Charger Current Controller
24
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417 q (408) 432-1900 FAX: (408) 434-0507q TELEX: 499-3977 q www.linear-tech.com
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Dimensions in inches (millimeters) unless otherwise noted. G Package 36-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640)
0.499 - 0.509* (12.67 - 12.93) 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19
0.301 - 0.311 (7.65 - 7.90)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 0.068 - 0.078 (1.73 - 1.99)
0 - 8
0.0256 (0.65) BSC
0.010 - 0.015 (0.25 - 0.38)
0.002 - 0.008 (0.05 - 0.21)
G36 SSOP 1196
COMMENTS
5V at 200mA from 2 Cells, IQ = 10A in Shutdown Fixed Frequency, Ultrahigh Efficiency Fixed Frequency, PLL Lockable, Ultrahigh Efficiency Protected Power Management Building Block 1.5A Internal Switch, Precision 0.5% Reference Adapter Current Limit Loop 5V Standby in Shutdown 96% Efficiency When Used with LTC1435 For Dual Loop Applications
1479f LT/TP 0697 7K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1996

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