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19-1566; Rev 0; 10/99
Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
General Description
The MAX1645 is a high-efficiency battery charger capable of charging batteries of any chemistry type. It uses the Intel System Management Bus (SMBus) to control voltage and current charge outputs. When charging lithium-ion (Li+) batteries, the MAX1645 automatically transitions from regulating current to regulating voltage. The MAX1645 can also limit line input current so as not to exceed a predetermined current drawn from the DC source. A 175sec charge safety timer prevents "runaway charging" should the MAX1645 stop receiving charging voltage/current commands. The MAX1645 employs a next-generation synchronous buck control circuitry that lowers the minimum input-tooutput voltage drop by allowing the duty cycle to exceed 99%. The MAX1645 can easily charge one to four series Li+ cells. o Input Current Limiting o 175sec Charge Safety Timeout o 128mA Wake-Up Charge o Charges Any Chemistry Battery: Li+, NiCd, NiMH, Lead Acid, etc. o Intel SMBus 2-Wire Serial Interface o Compliant with Level 2 Smart Battery Charger Spec. Rev. 1.0 o +8V to +28V Input Voltage Range o Up to 18.4V Battery Voltage o 11-Bit Battery Voltage Setting o 0.8% Output Voltage Accuracy with Internal Reference o 3A max Battery Charge Current o 6-Bit Charge Current Setting o 99.99% max Duty Cycle for Low-Dropout Operation o Load/Source Switchover Drivers o >97% Efficiency
Features
MAX1645
Applications
Notebook Computers Point-of-Sale Terminals Personal Digital Assistants
Pin Configuration
TOP VIEW
DCIN 1 LDO 2 CLS 3 REF 4 CCS 5 CCI 6 CCV 7 GND 8 BATT 9 DAC 10 VDD 11 THM 12 SCL 13 SDA 14 28 CVS 27 PDS 26 CSSP 25 CSSN 24 BST
Ordering Information
PART MAX1645EEI TEMP. RANGE -40C to +85C PIN-PACKAGE 28 QSOP
MAX1645
23 DHI 22 LX 21 DLOV 20 DLO 19 PGND 18 CSIP 17 CSIN 16 PDL 15 INT
Typical Operating Circuit appears at end of data sheet.
QSOP
SMBus is a trademark of Intel Corp.
________________________________________________________________ Maxim Integrated Products
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
ABSOLUTE MAXIMUM RATINGS
DCIN, CVS, CSSP, CSSN, LX to GND....................-0.3V to +30V CSSP to CSSN, CSIP to CSIN ...............................-0.3V to +0.3V PDS, PDL to GND ...................................-0.3V to (VCSSP + 0.3V) BST to LX..................................................................-0.3V to +6V DHI to LX ...................................................-0.3V to (VBST + 0.3V) CSIP, CSIN, BATT to GND .....................................-0.3V to +22V LDO to GND .....................-0.3V to (lower of 6V or VDCIN + 0.3V) DLO to GND ...........................................-0.3V to (VDLOV + 0.3V) REF, DAC, CCV, CCI, CCS, CLS to GND.....-0.3V to (VLDO + 0.3V) VDD, SCL, SDA, INT, DLOV to GND.........................-0.3V to +6V THM to GND ...............................................-0.3V to (VDD + 0.3V) PGND to GND .......................................................-0.3V to +0.3V LDO Continuous Current.....................................................50mA Continuous Power Dissipation (TA = +70C) 28-Pin QSOP (derate 10.8mW/C above +70C).......860mW Operating Temperature Range ...........................-40C to +85C Storage Temperature.........................................-60C to +150C Lead Temperature (soldering, 10sec) .............................+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
(Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER GENERAL SPECIFICATIONS DCIN Typical Operating Range DCIN Supply Current DCIN Supply Current Charging Inhibited DCIN Undervoltage Threshold LDO Output Voltage VDD Input Voltage Range (Note 1) VDD Undervoltage Threshold VDD Quiescent Current REF Output Voltage BATT Undervoltage Threshold (Note 2) PDS Charging Source Switch Turn-Off Threshold PDS Charging Source Switch Threshold Hysteresis PDS Output Low Voltage, PDS Below CSSP PDS Turn-On Current PDS Turn-Off Current PDL Load Switch Turn-Off Threshold VPDL-OFF VPDS-OFF VPDS-HYS IDD VREF VLDO VDCIN IDCIN 8V < VDCIN < 28V 8V < VDCIN < 28V When AC_PRESENT switches DCIN rising DCIN falling 7 5.15 2.8 VDD rising VDD falling 2.1 2.55 2.5 80 4.066 2.4 50 100 8 100 10 -150 100 200 10 150 50 -100 -50 4.096 150 4.126 2.8 150 300 12 300 8 1.7 0.7 7.5 7.4 5.4 5.65 5.65 2.8 28 6 2 7.85 V mA mA V V V V A V V mV mV V A mA mV SYMBOL CONDITIONS MIN TYP MAX UNITS
8V < VDCIN < 28V, 0 < ILDO < 15mA 8V < VDCIN < 28V When the SMB responds to commands
0 < VDCIN < 6V, VDD = 5V, VSCL = 5V, VSDA = 5V 0 < IREF < 200A When ICHARGE drops to 128mA VCVS referred to VBATT, VCVS falling VCVS referred to VBATT IPDS = 0 PDS = CSSP VPDS = VCSSP - 2V, VDCIN = 16V VCVS referred to VBATT, VCVS rising
2
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER PDL Load Switch Threshold Hysteresis PDL Turn-Off Current PDL Turn-On Resistance CVS Input Bias Current SYMBOL VPDL-HYS CONDITIONS VCVS referred to VBATT VCSSN - VPDL = 1V PDL to GND VCVS = 28V ChargingVoltage() = 0x41A0 BATT Full-Charge Voltage V0 ChargingVoltage() = 0x3130 ChargingVoltage() = 0x20D0 Charging Voltage() = 0x1060 ChargingCurrent() = 0x0BC0 BATT Charge Current (Note 3) I0 RCS = 50m ChargingCurrent() = 0x0080 VCLS = 4.096V VCLS = 2.048V 16.666 12.492 8.333 4.150 2.798 61.6 4.714 2.282 20 0 Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V, charge inhibited Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V, VDCIN = 0 VCSSP = VCSSN = VDCIN = 0 to 28V VCSSP = CCSSN = VDCIN = 0 to 28V VCSSP = VCSSN = 28V, VDCIN = 0 From BATT to CCV VCLS = VREF/2 to VREF From BATT to CCV, ChargingVoltage() = 0x41A0, VBATT = 16.8V From CSIP/SCIN to CCI, ChargingCurrent() = 0x0BC0, VCSIP - VCSIN = 150.4mV From CSSP/CSSN to CCS, VCLS = 2.048V, VCSSP - VCSSN = 102.4mV VCCV = VCCI = VCCS = 0.25V to 2V -700 -100 -5 -100 -100 -1 200 -1 0.111 0.5 0.5 150 500 0.05 0.222 1 1 300 1 0.444 2 2 600 540 35 MIN 100 6 50 TYP 200 12 100 6 16.8 12.592 8.4 4.192 3.008 128 5.12 2.56 128 150 20 16.934 12.692 8.467 4.234 3.218 194.4 5.526 2.838 200 20 700 100 5 1000 100 1 A mA A mA V A A A A mA A V/V A A/mV A/mV A/mV mV V MAX 300 UNITS mV mA k A
MAX1645
DCIN Source Current Limit (Note 3) BATT Undervoltage Charge Current BATT/CSIP/CSIN Input Voltage Range Total BATT Input Bias Current Total BATT Quiescent Current Total BATT Standby Current CSSP Input Bias Current CSSN Input Bias Current CSSP/CSSN Quiescent Current Battery Voltage-Error Amp DC Gain CLS Input Bias Current Battery Voltage-Error Amp Transconductance Battery Current-Error Amp Transconductance Input Current-Error Amp Transconductance CCV/CCI/CCS Clamp Voltage (Note 4)
RCSS = 40m
VBATT = 1V, RCSI = 50m
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Minimum Off-Time Maximum On-Time Maximum Duty Cycle LX Input Bias Current LX Input Quiescent Current BST Supply Current DLOV Supply Current Inductor Peak Current Limit DHI Output Resistance DLO Output Resistance VDCIN = 28V, VBATT = VLX = 20V VDCIN = 0, VBATT = VLX = 20V DHI high VDLOV = VLDO, DLO low RCSI = 50m DHI high or low, VBST - VLX = 4.5V DLO high or low, VDLOV = 4.5V VTHM = 4% of VDD to 96% of VDD, VDD = 2.8V to 5.65V VDD = 2.8V to 5.65V, VTHM falling VDD = 2.8V to 5.65V, VTHM falling VDD = 2.8V to 5.65V, VTHM falling VDD = 2.8V to 5.65V, VTHM falling All 4 comparators, VDD = 2.8V to 5.65V 5.0 6 5 6.0 6 6 SYMBOL tOFF tON CONDITIONS MIN 1 5 99 TYP 1.25 10 99.99 200 500 1 15 10 7.0 14 14 MAX 1.5 15 UNITS s ms % A A A A A
DC-TO-DC CONVERTER SPECIFICATIONS
THERMISTOR COMPARATOR SPECIFICATIONS THM Input Bias Current Thermistor Overrange Threshold Thermistor Cold Threshold Thermistor Hot Threshold Thermistor Underrange Threshold Thermistor Comparator Threshold Hysteresis SDA/SCL Input Low Voltage SDA/SCL Input High Voltage SDA/SCL Input Hysteresis SDA/SCL Input Bias Current SDA Output Low Sink Current INT Output High Leakage INT Output Low Voltage SCL High Period SCL Low Period Start Condition Setup Time from SCL Start Condition Hold Time from SCL SDA Setup Time from SCL SDA Hold Time from SCL tHIGH tLOW tSU:STA tHD:STA tSU:DAT tHD:DAT VSDA = 0.4V VINT = 5.65V IINT = 1mA 4 4.7 4.7 4 250 0 25 -1 6 1 200 1.4 220 1 -1 89.5 74 22 6 91 75.5 23.5 7.5 1 1 92.5 77 25 9 A % of VDD % of VDD % of VDD % of VDD % of VDD
SMB INTERFACE LEVEL SPECIFICATIONS (VDD = 2.8V to 5.65V) 0.6 V V mV A mA A mV s s s s ns ns
SMB INTERFACE TIMING SPECIFICATIONS (VDD = 2.8V to 5.65V, Figures 4 and 5)
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SDA Output Data Valid from SCL Maximum Charge Period Without a ChargingVoltage() or Charging Current() Loaded SYMBOL tDV tWDT 140 175 CONDITIONS MIN TYP MAX 1 210 UNITS s sec
MAX1645
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = -40C to +85C, unless otherwise noted. Guaranteed by design.) PARAMETER GENERAL SPECIFICATIONS DCIN Typical Operating Range DCIN Supply Current DCIN Supply Current Charging Inhibited DCIN Undervoltage Threshold LDO Output Voltage VDD Input Voltage Range (Note 1) VDD Undervoltage Threshold VDD Quiescent Current REF Output Voltage BATT Undervoltage Threshold (Note 2) PDS Charging Source Switch Turn-Off Threshold PDS Charging Source Switch Threshold Hysteresis PDS Output Low Voltage, PDS Below CSSP PDS Turn-On Current PDS Turn-Off Current PDL Load Switch Turn-Off Threshold PDL Load Switch Threshold Hysteresis PDL Turn-Off Current VPDL-OFF VPDL-HYS VPDS-OFF VPDS-HYS IDD VREF VLDO VDCIN IDCIN 8V < VDCIN < 28V 8V < VDCIN < 28V When AC_PRESENT switches DCIN rising DCIN falling 7 5.15 2.8 VDD rising VDD falling 2.1 150 4.035 2.4 50 100 8 100 10 -150 100 6 -50 300 4.157 2.8 150 300 12 300 5.65 5.65 2.8 8 28 6 2 7.85 V mA mA V V V V A V V mV mV V A mA mV mV mA SYMBOL CONDITIONS MIN MAX UNITS
8V < VDCIN < 28V, 0 < ILDO < 15mA 8V < VDCIN < 28V When the SMB responds to commands
0 < VDCIN < 6V, VDD = 5V, VSCL = 5V, VSDA = 5V 0 < IREF < 200A When ICHARGE drops to 128mA VCVS referred to VBATT, VCVS falling VCVS referred to VBATT IPDS = 0 PDS = CSSP VPDS = VCSSP - 2V, VDCIN = 16V VCVS referred to VBATT, VCVS rising VCVS referred to VBATT VCSSN - VPDL = 1V
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = -40C to +85C, unless otherwise noted. Guaranteed by design.) PARAMETER PDL Turn-On Resistance CVS Input Bias Current ERROR AMPLIFIER SPECIFICATIONS ChargingVoltage() = 0x41A0 BATT Full-Charge Voltage V0 ChargingVoltage() = 0x3130 ChargingVoltage() = 0x20D0 ChargingVoltage() = 0x1060 ChargingCurrent() = 0x0BC0 BATT Charge Current (Note 3) I0 RCSI = 50m ChargingCurrent() = 0x0080 VCLS = 4.096V VCLS = 2.048V 16.532 12.391 8.266 4.124 2.608 15.2 4.358 2.054 20 0 Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V, charge inhibited Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V, VDCIN = 0 VCSSP = VCSSN = VDCIN = 28V VCSSP = VCSSN = VDCIN = 28V VCSSP = VCSSN = 28V, VDCIN = 0 From BATT to CCV VCLS = VREF/2 to VREF From BATT to CCV, ChargingVoltage() = 0x41A0, VBATT = 16.8V From CSIP/CSIN to CCI, ChargingCurrent() = 0x0BC0, VCSIP -VCSIN = 150.4mV From CSSP/CSSN to CCS, VCLS = 2.048V, VCSSP - VCSSN = 102.4mV VCCV = VCCI = VCCS = 0.25V to 2V -700 -100 -5 -100 -100 -1 200 -1 0.111 0.5 0.5 150 1 0.444 2 2 600 17.068 12.793 8.534 4.260 3.408 240.8 5.882 3.006 200 20 700 100 5 1000 100 1 A mA A mA V A A A A A A V/V A A/mV A/mV A/mV mV V SYMBOL PDL to GND VCVS = 28V CONDITIONS MIN 50 MAX 150 20 UNITS k A
DCIN Source Current Limit (Note 3) BATT Undervoltage Charge Current BATT/CSIP/CSIN Input Voltage Range Total BATT Input Bias Current Total BATT Quiescent Current Total BATT Standby Current CSSP/Input Bias Current CSSN Input Bias Current CSSP/CSSN Quiescent Current Battery Voltage-Error Amp DC Gain CLS Input Bias Current Battery Voltage-Error Amp Transconductance Battery Current-Error Amp Transconductance Input Current-Error Amp Transconductance CCV/CCI/CCS Clamp Voltage (Note 4) DC-TO-DC CONVERTER SPECIFICATIONS Minimum Off-Time Maximum On-Time Maximum Duty Cycle 6 tOFF tON
RCSS = 40m
VBATT = 1V, RCSI = 50m
1 5 99
1.5 15
s ms %
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = -40C to +85C, unless otherwise noted. Guaranteed by design.) PARAMETER LX Input Bias Current LX Input Quiescent Current BST Supply Current DLOV Supply Current Inductor Peak Current Limit DHI Output Resistance DLO Output Resistance SYMBOL CONDITIONS VDCIN = 28V, VBATT = VLX = 20V VDCIN = 0, VBATT = VLX = 20V DHI high VDLOV = VLDO, DLO low RCSI = 50m DHI high or low, VBST - VLX = 4.5V DLO high or low, VDLOV = 4.5V VTHM = 4% of VDD to 96% of VDD, VDD = 2.8V to 5.65V VDD = 2.8V to 5.65V, VTHM falling VDD = 2.8V to 5.65V, VTHM falling VDD = 2.8V to 5.65V, VTHM falling VDD = 2.8V to 5.65V, VTHM falling 5.0 MIN MAX 500 1 15 10 7.0 14 14 UNITS A A A A A
MAX1645
THERMISTOR COMPARATOR SPECIFICATIONS THM Input Bias Current Thermistor Overrange Threshold Thermistor Cold Threshold Thermistor Hot Threshold Thermistor Underrange Threshold SDA/SCL Input Low Voltage SDA/SCL Input High Voltage SDA/SCL Input Bias Current SDA Output Low Sink Current INT Output High Leakage INT Output Low Voltage SCL High Period SCL Low Period Start Condition Setup Time from SCL Start Condition Hold Time from SCL SDA Setup Time from SCL SDA Hold Time from SCL tHIGH tLOW tSU:STA tHD:STA tSU:DAT tHD:DAT VSDA = 0.4V VINT = 5.65V IINT = 1mA 4 4.7 4.7 4 250 0 1.4 -1 6 1 200 1 -1 89.5 74 22 6 1 92.5 77 25 9 A % of VDD % of VDD % of VDD % of VDD
SMB INTERFACE LEVEL SPECIFICATIONS (VDD = 2.8V to 5.65V) 0.6 V V A mA A mV s s s s ns ns
SMB INTERFACE TIMING SPECIFICATIONS (VDD = 2.8V to 5.65V, Figures 4 and 5)
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = -40C to +85C, unless otherwise noted. Guaranteed by design.) PARAMETER SDA Output Data Valid from SCL Maximum Charge Period Without a ChargingVoltage() or Charging Current() loaded Note 1: Note 2: Note 3: Note 4: SYMBOL tDV CONDITIONS MIN MAX 1 UNITS s
tWDT
140
210
sec
Guaranteed by meeting the SMB timing specs. The charger reverts to a trickle-charge mode of ICHARGE = 128mA below this threshold. Does not include current-sense resistor tolerance. Voltage difference between CCV, and CCI or CCS when one of these three pins is held low and the others try to pull high.
Typical Operating Characteristics
(Circuit of Figure 1, VDCIN = 20V, TA = +25C, unless otherwise noted.)
LOAD-TRANSIENT RESPONSE (BATTERY REMOVAL AND REINSERTION)
MAX1645 toc01
LOAD-TRANSIENT RESPONSE (STEP IN LOAD CURRENT)
16V VBATT 14V 12V
MAX1645 toc02
LDO LINE REGULATION
ILOAD = 0 2A 0 5.55 5.50 VLDO (V) 5.45 5.40 5.35 1V 5.30 5.25 0
MAX1645 toc03
4A
5.60
VBATT
IBATT
1A 0 CCV CCI CCI CCV CCV CCI 0.5V 1.5V 1V IBATT
CCS
CCI CCI
2A CCI
VCCV/VCCI
VCCV/VCCI
CCS
CCS
BATTERY REMOVED 2ms/div BATTERY INSERTED ChargingVoltage() = 15000mV ChargingCurrent() = 1000mA
1ms/div ChargingCurrent() = 3008mA VBATT = 16V LOAD STEP: 0A TO 2A ISOURCE LIMIT = 2.5A
5.20 5 10 15 20 25 30 VDCIN (V)
LDO LOAD REGULATION
MAX1645 toc04
REFERENCE VOLTAGE LOAD REGULATION
MAX1645 toc05
REFERENCE VOLTAGE vs. TEMPERATURE
MAX1645 toc06
5.60 5.55 5.50 VLDO (V)
4.100
4.110 4.105 4.100
4.098
VREF (V)
VREF (V)
5.45 5.40 5.35 5.30 5.25 5.20 0 2 4 6 8 10 12 14 16 18 20 LOAD CURRENT (mA)
4.096
4.095 4.090
4.094
4.092
4.085 4.080 -40
4.090 0 50 100 150 200 250 300 LOAD CURRENT (A)
-20
0
20
40
60
80
100
TEMPERATURE (C)
8
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VDCIN = 20V, TA = +25C, unless otherwise noted.)
EFFICIENCY vs. BATTERY CURRENT (VOLTAGE-CONTROL LOOP)
MAX1645 toc07
EFFICIENCY vs. BATTERY CURRENT (CURRENT-CONTROL LOOP)
MAX1645 toc08
OUTPUT VI CHARACTERISTICS
DROP IN BATT OUTPUT VOLTAGE (%)
MAX1645 toc09
100 95 90 EFFICIENCY (%) 85 80 75 70 65 60 55 50 0 A: VDCIN = 20V, ChargingVoltage() = 16.8V B: VDCIN = 16V, ChargingVoltage() = 8.4V 500 1000 1500 2000 2500
A B
100 95 90 EFFICIENCY (%) 85 80 75 70 65 60 55 50 A: VDCIN = 20V, VBATT = 16.8V B: VDCIN = 16V, VBATT = 8.4V 0 500 1000 1500 2000 2500 A B
0.001
0.01
0.1
1.0 ChargingVoltage() = 16,800mV ChargingCurrent() = 3008mA 10 0 500 1000 1500 2000 2500 3000 3500 LOAD CURRENT (mA)
3000
3000
BATTERY CURRENT (mA)
ChargingCurrent() (CODE)
BATT VOLTAGE ERROR vs. ChargingVoltage() CODE
MAX1645 toc10
CURRENT-SETTING ERROR vs. ChargingCurrent() CODE
4 BATT CURRENT ERROR (%) 3 2 1 0 -1 -2 -3 VBATT = 12.6V MEASURED AT AVAILABLE CODES 0 500 1000 1500 2000 2500 3000
MAX1645 toc11
0.3 0.2 0.1 0 -0.1 -0.2 -0.3 0000 4000 8000 12000 16000
5
BATT VOLTAGE ERROR (%)
IBATT = 0 MEASURED AT AVAILABLE CODES 20000
-4 -5
ChargingVoltage() (CODE)
ChargingCurrent() (CODE)
SOURCE/BATT CURRENT vs. LOAD CURRENT WITH SOURCE CURRENT LIMIT
MAX1645 toc12
SOURCE/BATT CURRENT vs. VBATT WITH SOURCE CURRENT LIMIT
MAX1645 toc13
3.5 3.0 SOURCE/BATT CURRENT (A) IIN 2.5 2.0 1.5 1.0 0.5 0 0 0.5 1.0 1.5 2.0
3.5 3.0 SOURCE/BATT CURRENT (A) IIN 2.5 2.0 1.5 1.0 0.5 0 ILOAD = 2A VCLS = 2V RCSS = 40m ChargingVoltage() = 18,432mV ChargingCurrent() = 3008mA SOURCE CURRENT LIMIT = 2.5A 0 2 4 6 8
VCLS = 2V RCSS = 40m VBATT = 16.8V SOURCE CURRENT LIMIT = 2.5A ChargingCurrent() = 3008mA ChargingVoltage() = 18,432mV
IBATT
IBATT
2.5
10 12 14 16 18 20
LOAD CURRENT (A)
VBATT (V)
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Pin Description
PIN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 NAME DCIN LDO CLS REF CCS CCI CCV GND BATT DAC VDD THM SCL SDA INT PDL CSIN CSIP PGND DLO DLOV LX DHI BST CSSN CSSP PDS CVS DC Supply Voltage Input 5.4V Linear-Regulator Voltage Output. Bypass with a 1F capacitor to GND. Source Current Limit Input 4.096V Reference Voltage Output Charging Source Compensation Capacitor Connection. Connect a 0.01F capacitor from CCS to GND. Battery Current-Loop Compensation Capacitor Connection. Connect a 0.01F capacitor from CCI to GND. Battery Voltage-Loop Compensation Capacitor Connection. Connect a 10k resistor in series with a 0.01F capacitor to GND. Ground Battery Voltage Output DAC Voltage Output Logic Circuitry Supply Voltage Input (2.8V to 5.65V) Thermistor Voltage Input SMB Clock Input SMB Data Input/Output. Open-drain output. Needs external pull-up. Interrupt Output. Open-drain output. Needs external pull-up. PMOS Load Switch Driver Output Battery Current-Sense Negative Input Battery Current-Sense Positive Input Power Ground Low-Side NMOS Driver Output Low-Side NMOS Driver Supply Voltage. Bypass with 0.1F capacitor to GND. Inductor Voltage Sense Input High-Side NMOS Driver Output High-Side Driver Bootstrap Voltage Input. Bypass with 0.1F capacitor to LX. Charging Source Current-Sense Negative Input Charging Source Current-Sense Positive Input Charging Source PMOS Switch Driver Output Charging Source Voltage Input FUNCTION
10
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Detailed Description
The MAX1645 consists of current-sense amplifiers, an SMBus interface, transconductance amplifiers, reference circuitry, and a DC-DC converter (Figure 2). The DC-DC converter generates the control signals for the external MOSFETs to maintain the voltage and the current set by the SMBus interface. The MAX1645 features a voltage-regulation loop and two current-regulation loops. The loops operate independently of each other. The voltage-regulation loop monitors BATT to ensure that its voltage never exceeds the voltage set point (V0). The battery current-regulation loop monitors current delivered to BATT to ensure that it never exceeds the current-limit set point (I0). The battery current-regulation loop is in control as long as BATT voltage is below V0. When BATT voltage reaches V0, the current loop no longer regulates. A third loop reduces the battery-charging current when the sum of the system (the main load) and the battery charger input current exceeds the charging source current limit. loaded down. An internal amplifier compares the voltage between CSSP and CSSN to the voltage at CLS/20. V CLS is set by a resistor divider between REF and GND. The input source current is the sum of the device current, the charge input current, and the load current. The device current is minimal (6mA max) in comparison to the charge and load currents. The charger input current is generated by the DC-DC converter; therefore, the actual source current required is determined as follows: ISOURCE = ILOAD + [(ICHARGE * VBATT) / (VIN * )] where is the efficiency of the DC-DC converter (typically 85% to 95%). VCLS determines the threshold voltage of the CSS comparator. R3 and R4 (Figure 1) set the voltage at CLS. Sense resistor R1 sets the maximum allowable source current. Calculate the maximum current as follows: IMAX = VCLS / (20 * R1) (Limit V CSSP - V CSSN to between 102.4mV and 204.8mV.) The configuration in Figure 1 provides an input current limit of: IMAX = (2.048V / 20) / 0.04 = 2.56A
Setting Output Voltage
The MAX1645's voltage DAC has a 16mV LSB and an 18.432V full scale. The SMBus specification allows for a 16-bit ChargingVoltage() command that translates to a 1mV LSB and a 65.535V full-scale voltage; therefore, the ChargingVoltage() value corresponds to the output voltage in millivolts. The MAX1645 ignores the first four LSBs and uses the next 11 LSBs to control the voltage DAC. All codes greater than or equal to 0b0100 1000 0000 0000 (18432mV) result in a voltage overrange, limiting the charger voltage to 18.432V. All codes below 0b0000 0100 0000 0000 (1024mV) terminate charging.
LDO Regulator
The LDO provides a +5.4V supply derived from DCIN and can deliver up to 15mA of current. The LDO sets the gate-drive level of the NMOS switches in the DC-DC converter. The drivers are actually powered by DLOV and BST, which must be connected to LDO through a lowpass filter and a diode as shown in Figure 1. See also the MOSFET Drivers section. The LDO also supplies the 4.096V reference and most of the control circuitry. Bypass LDO with a 1F capacitor.
Setting Output Current
The MAX1645's current DAC has a 64mA LSB and a 3.008A full scale. The SMBus specification allows for a 16-bit ChargingCurrent() command that translates to a 1mA LSB and a 65.535A full-scale current; the ChargingCurrent() value corresponds to the charging voltage in milliamps. The MAX1645 drops the first six LSBs and uses the next six LSBs to control the current DAC. All codes above 0b00 1011 1100 0000 (3008mA) result in a current overrange, limiting the charger current to 3.008A. All codes below 0b0000 0000 1000 0000 (128mA) turn the charging current off. A 50m sense resistor (R2 in Figure 1) is required to achieve the correct CODE/current scaling.
VDD Supply This input provides power to the SMBus interface and the thermistor comparators. Typically connect VDD to LDO or, to keep the SMBus interface of the MAX1645 active while the supply to DCIN is removed, connect an external supply to VDD.
Input Current Limiting
The MAX1645 limits the current drawn by the charger when the load current becomes high. The device limits the charging current so the AC adapter voltage is not
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
ADAPTER IN D4 1N4148 C5 1F R13 1k PDS CVS DCIN C23 0.1F CSSP C20, 1F R1 0.04 R15 4.7 C6 1F LOAD D3 1N4148 R12 33 R14 4.7 P1 FDS6675
D1 1N5821
C1 22F
C2 22F
REF C7 1F R3 100k CLS R4 100k GND DAC C8 0.1F CCV R5 10k C9 0.01F C10 0.01F CCS C11 0.01F
MAX1645
CSSN LDO
C19, 1F
BST DLOV C16 0.1F DHI N1 FDS6680 C14 0.1F
CCI LX
DLO
N2 FDS6612A
D2 1N5821
L1 22H
PGND R11 1 CSIP C18 0.1F C24 0.1F CSIN PDL R16 1
R2 0.05
P2 FDS6675
C4 22F
C3 22F
BATT R7 10k THM VDD C12 1F R10 10k SCL SDA INT R8 R9 10k 10k C13 1.5nF HOST R6 10k BATTERY
Figure 1. Typical Application Circuit 12 ______________________________________________________________________________________
Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
BST
MAX1645
CSSP CSS CSSN GMS LVC CLS DLO CSI CSIN BATT CCS CCI CCV GMV CVS BATT GMI DC-DC DLOV DLO PGND LX DHI DHI
CSIP
PDL
PDS
PDS
PDL
VDD SCL SDA INT DACI SMB REF DACV VL
DCIN LDO
REF GND
THM
TEMP
DAC
Figure 2. Functional Diagram
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Operating Conditions
The MAX1645 changes its operation depending on the voltages at DCIN, BATT, VDD, and THM. Several important operating states follow: * AC Present. When DCIN is > 7.5V, the battery is considered to be in an AC Present state. In this condition, both the LDO and REF will function properly and battery charging is allowed. When AC is present, the AC_PRESENT bit (bit 15) in the ChargerStatus() register is set to "1." * Power Fail. When DCIN is < BATT + 0.3V, the MAX1645 is in the Power Fail state, since the charger doesn't have enough input voltage to charge the battery. In Power Fail, the PDS input PMOS switch is turned off and the POWER_FAIL bit (bit 13) in the ChargerStatus() register is set to "1." * Battery Present. When THM is < 91% of VDD, the battery is considered to be present. The MAX1645 uses the THM pin to detect when a battery is connected to the charger. When the battery is present, the BATTERY_PRESENT bit (bit 14) in the ChargerStatus() register is set to "1" and charging can proceed. When the battery is not present, all of the MAX1645 registers are reset. With no battery present, the charger will still try to regulate the BATT pin voltage at 18.432V with 128mA of current compliance. * Battery Undervoltage. When BATT < 2.5V, the battery is in an undervoltage state. This causes the charger to reduce its current compliance to 128mA. The content of the ChargingCurrent() register is unaffected and, when the BATT voltage exceeds 2.7V, normal charging resumes. ChargingVoltage() is unaffected and can be set as low as 1.024V. * VDD Undervoltage. When VDD < 2.5V, the VDD supply is in an undervoltage state, and the SMBus interface will not respond to commands. Coming out of the undervoltage condition, MAX1645 will be in its Power-On Reset state. No charging will occur when VDD is under voltage. device and does not initiate communication on the bus. It receives commands and responds to queries for status information. Figure 3 shows examples of the SMBus Write-Word and Read-Word protocols, and Figures 4 and 5 show the SMBus serial-interface timing. Each communication with the MAX1645 begins with the MASTER issuing a START condition that is defined as a falling edge on SDA with SCL high and ends with a STOP condition defined as a rising edge on SDA with SCL high. Between the START and STOP conditions, the device address, the command byte, and the data bytes are sent. The MAX1645 device address is 0x12 and supports the charger commands as described in Tables 1-6.
Battery Charger Commands
ChargerSpecInfo() The ChargerSpecInfo() command uses the Read-Word protocol (Figure 3b). The command code for ChargerSpecInfo() is 0x11 (0b00010001). Table 1 lists the functions of the data bits (D0-D15). Bit 0 refers to the D0 bit in the Read-Word protocol. The MAX1645 is version 1.0; therefore, the ChargerSpecInfo() command returns 0x01. ChargerMode() The ChargerMode() command uses the Write-Word protocol (Figure 3a). The command code for ChargerMode() is 0x12 (0b00010010). Table 2 lists the functions of the data bits (D0-D15). Bit 0 refers to the D0 bit in the Write-Word protocol. To charge a battery that has a thermistor impedance in the HOT range (i.e., THERMISTOR_HOT = 1 and THERMISTOR_UR = 0), the host must use the Charger Mode() command to clear HOT_STOP after the battery is inserted. The HOT_STOP bit returns to its default power-up condition ("1") whenever the battery is removed. ChargerStatus() The ChargerStatus() command uses the Read-Word protocol (Figure 3b). The command code for Charger Status() is 0x13 (0b00010011). Table 3 describes the functions of the data bits (D0-D15). Bit 0 refers to the D0 bit in the Read-Word protocol. The ChargerStatus() command returns information about thermistor impedance and the MAX1645's internal state. The latched bits, THERMISTOR_HOT and ALARM_INHIBITED, are cleared whenever BATTERY_ PRESENT = 0 or ChargerMode() is written with POR_RESET = 1. The ALARM_INHIBITED status bit can also be cleared by writing a new charging current OR charging voltage.
SMBus Interface
The MAX1645 receives control inputs from the SMBus interface. The serial interface complies with the SMBus specification (refer to the System Management Bus Specification from Intel Corporation). Charger functionality complies with the Intel/Duracell Smart Charger Specification for a Level 2 charger. The MAX1645 uses the SMBus Read-Word and WriteWord protocols to communicate with the battery being charged, as well as with any host system that monitors the battery-to-charger communications as a Level 2 SMBus charger. The MAX1645 is an SMBus slave
14
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
a) Write-Word Format
S SLAVE ADDRESS 7 bits MSB LSB Preset to 0b0001001 W 1b 0 ACK 1b 0 COMMAND BYTE 8 bits MSB LSB ChargerMode() = 0x12 ChargingCurrent() = 0x14 ChargerVoltage() = 0x15 AlarmWarning() = 0x16 ACK 1b 0 LOW DATA BYTE 8 bits MSB LSB D7 D0 ACK 1b 0 HIGH DATA BYTE 8 bits MSB LSB D15 D8 ACK 1b 0 P
b) Read-Word Format
S SLAVE W ACK ADDRESS 7 bits MSB LSB Preset to 0b0001001 1b 0 1b 0 COMMAND BYTE 8 bits MSB LSB ChargerSpecInfo() = 0x11 ChargerStatus() = 0x13 ACK S 1b 0 SLAVE ADDRESS 7 bits MSB LSB Preset to 0b0001001 R ACK 1b 1 1b 0 LOW DATA BYTE 8 bits MSB LSB D7 D0 ACK 1b 0 HIGH DATA BYTE 8 bits MSB LSB D15 D8 NACK P 1b 1
Legend: S = Start Condition or Repeated Start Condition ACK = Acknowledge (logic low) W = Write Bit (logic low) MASTER TO SLAVE SLAVE TO MASTER
P = Stop Condition NACK = NOT Acknowledge (logic high) R = Read Bit (logic high)
Figure 3. SMBus a) Write-Word and b) Read-Word Protocols
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
START CONDITION MOST SIGNIFICANT ADDRESS BIT (A6) CLOCKED INTO SLAVE A5 CLOCKED INTO SLAVE A4 CLOCKED INTO SLAVE A3 CLOCKED INTO SLAVE
SCL
tHD:STA
tLOW
tHIGH
SDA
tSU:STA
tSU:DAT
tHD:DAT
tSU:DAT
tHD:DAT
Figure 4. SMBus Serial Interface Timing--Address
R/W BIT CLOCKED INTO SLAVE
ACKNOWLEDGE BIT CLOCKED INTO MASTER
MOST SIGNIFICANT BIT OF DATA CLOCKED INTO MASTER
SCL
SDA
SLAVE PULLING SDA LOW tDV tDV
Figure 5. SMBus Serial Interface Timing--Acknowledgment
16
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Table 1. ChargerSpecInfo()
BIT 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Command: 0x11 NAME CHARGER_SPEC CHARGER_SPEC CHARGER_SPEC CHARGER_SPEC SELECTOR_SUPPORT Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Returns a "1" for Version 1.0 Returns a "0" for Version 1.0 Returns a "0" for Version 1.0 Returns a "0" for Version 1.0 Returns a "0," indicating no smart battery selector functionality Returns a "0" Returns a "0" Returns a "0" Returns a "0" Returns a "0" Returns a "0" Returns a "0" Returns a "0" Returns a "0" Returns a "0" Returns a "0" DESCRIPTION
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Table 2. ChargerMode()
BIT 0 1 NAME INHIBIT_CHARGE ENABLE_POLLING DESCRIPTION 0* = Allow normal operation; clear the CHG_INHIBITED flip-flop. 1 = Turn off the charger; set the CHG_INHIBITED flip-flop. The CHG_INHIBITED flip-flop is not affected by any other commands. Not implemented 0 = No change. 1 = Change the ChargingVoltage() to 0xFFFF and the ChargingCurrent() to 0x00C0; clear the THERMISTOR_HOT and ALARM_INHIBITED flipflops. Not implemented 0* = Interrupt on either edge of the AC_PRESENT status bit. 1 = Do not interrupt because of an AC_PRESENT bit change. 0* = Interrupt on either edge of the BATTERY_PRESENT status bit. 1 = Do not interrupt because of a BATTERY_PRESENT bit change. 0* = Interrupt on either edge of the POWER_FAIL status bit. 1 = Do not interrupt because of a POWER_FAIL bit change. Not implemented Not implemented Not implemented 0 = The THERMISTOR_HOT status bit does not turn off the charger. 1* = The THERMISTOR_HOT status bit does turn off the charger. THERMISTOR_HOT is reset by either POR_RESET or BATTERY_PRESENT = 0 status bit. Not implemented Not implemented Not implemented Not implemented Not implemented
2
POR_RESET
3 4 5 6 7 8 9
RESET_TO_ZERO AC_PRESENT_MASK BATTERY_PRESENT_ MASK POWER_FAIL_MASK
10
HOT_STOP
11 12 13 14 15 Command: 0x12 *State at chip initial power-on (i.e., VDD from 0 to +3.3V)
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
Table 3. ChargerStatus()
BIT 0 1 2 3 4 5 6 NAME CHARGE_INHIBITED MASTER_MODE VOLTAGE_NOT_REG CURRENT_NOT_REG LEVEL_2 LEVEL_3 CURRENT_OR FUNCTION 0* = Ready to charge Smart Battery. 1 = Charger is inhibited, I(chg) = 0mA. This status bit returns the value of the CHG_INHIBITED flip-flop. Always returns "0" 0 = Battery voltage is limited at the set point. 1 = Battery voltage is less than the set point. 0 = Battery current is limited at the set point. 1 = Battery current is less than the set point. Always returns a "1" Always returns a "0" 0* = The ChargingCurrent() value is valid for the MAX1645. 1 = The ChargingCurrent() value exceeds the MAX1645 output range, i.e., programmed ChargingCurrent() exceeds 3008mA. 0 = The ChargingVoltage() value is valid for the MAX1645. 1* = The ChargingVoltage() value exceeds the MAX1645 output range, i.e., programmed ChargingVoltage() exceeds 1843mV. 0 = THM is < 91% of the reference voltage. 1 = THM is > 91% of the reference voltage. 0 = THM is < 75.5% of the reference voltage. 1 = THM is > 75.5% of the reference voltage. 0 = THM has not dropped to < 23.5% of the reference voltage. 1 = THM has dropped to < 23.5% of the reference voltage. THERMISTOR_HOT flip-flop cleared by BATTERY_PRESENT = 0 or writing a "1" into the POR_RESET bit in the ChargerMode() command. 0 = THM is > 7.5% of the reference voltage. 1 = THM is < 7.5% of the reference voltage. Returns the state of the ALARM_INHIBITED flip-flop. This flip-flop is set by either a watchdog timeout or by writing an AlarmWarning() command with bits 11, 12, 13, 14, or 15 set. This flip-flop is cleared by BATTERY_PRESENT = 0, writing a "1" into the POR_RESET bit in the ChargerMode() command, or by receiving successive ChargingVoltage() and ChargingCurrent() commands. POR: 0. 0 = The charging source voltage CVS is above the BATT voltage. 1 = The charging source voltage CVS is below the BATT voltage. 0 = No battery is present (based on THM input). 1 = Battery is present (based on THM input). 0 = DCIN is below the 7.5V undervoltage threshold. 1 = DCIN is above the 7.5V undervoltage threshold.
MAX1645
7
VOLTAGE_OR
8 9
THERMISTOR_OR THERMISTOR_COLD
10
THERMISTOR_HOT
11
THERMISTOR_UR
12
ALARM_INHIBITED
13 14 15 Command: 0x13
POWER_FAIL BATTERY_PRESENT AC_PRESENT
*State at chip initial power-on.
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Table 4. ChargerCurrent()
BIT 0 1 2 3 4 5 6 7 8 9 10 11 12-15 Command: 0x14 Charge Current, DACI 0 Charge Current, DACI 1 Charge Current, DACI 2 Charge Current, DACI 3 Charge Current, DACI 4 Charge Current, DACI 5 NAME Not used. Normally a 1mA weight. Not used. Normally a 2mA weight. Not used. Normally a 4mA weight. Not used. Normally an 8mA weight. Not used. Normally a 16mA weight. Not used. Normally a 32mA weight. 0 = Adds 0mA of charger-current compliance. 1 = Adds 64mA of charger-current compliance, 128mA min. 0 = Adds 0mA of charger-current compliance. 1 = Adds 128mA of charger-current compliance. 0 = Adds 0mA of charger-current compliance. 1 = Adds 256mA of charger-current compliance. 0 = Adds 0mA of charger-current compliance. 1 = Adds 512mA of charger-current compliance. 0 = Adds 0mA of charger-current compliance. 1 = Adds 1024mA of charger-current compliance. 0 = Adds 0mA of charger-current compliance. 1 = Adds 2048mA of charger-current compliance, 3008mA max. 0 = Adds 0mA of charger current compliance. 1 = Sets charger compliance into overrange, 3008mA. FUNCTION
20
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
Table 5. ChargingVoltage()
PIN 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Charge Voltage, DACV 0 Charge Voltage, DACV 1 Charge Voltage, DACV 2 Charge Voltage, DACV 3 Charge Voltage, DACV 4 Charge Voltage, DACV 5 Charge Voltage, DACV 6 Charge Voltage, DACV 7 Charge Voltage, DACV 8 Charge Voltage, DACV 9 Charge Voltage, DACV 10 Charge Voltage, Overrange BIT NAME Not used. Normally a 1mV weight. Not used. Normally a 2mV weight. Not used. Normally a 4mV weight. Not used. Normally an 8mV weight. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 16mV of charger-voltage compliance, 1.024V min. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 32mV of charger-voltage compliance, 1.024V min. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 64mV of charger-voltage compliance, 1.024V min. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 128mV of charger-voltage compliance, 1.024V min. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 256mV of charger-voltage compliance, 1.024V min. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 512mV of charger-voltage compliance, 1.024V min. 0 = Adds 0mA of charger-voltage compliance. 1 = Adds 1024mV of charger-voltage compliance. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 2048mV of charger-voltage compliance. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 4096mV of charger-voltage compliance. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 8192mV of charger-voltage compliance. 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 16384mV of charger-voltage compliance, 18432mV max. 0 = Adds 0mV of charger-voltage compliance. 1 = Sets charger compliance into overrange, 18432mV. FUNCTION
MAX1645
Command: 0x15
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Table 6. AlarmWarning()
BIT 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Command: 0x16 BIT NAME Error Code Error Code Error Code Error Code FULLY_DISCHARGED FULLY_CHARGED DISCHARGING INITIALIZING REMAINING_TIME_ ALARM REMAINING_CAPACITY_ ALARM Reserved TERMINATE_ DISCHARGE_ALARM OVER_TEMP_ALARM OTHER_ALARM TERMINATE_CHARGE_ ALARM OVER_CHARGE_ALARM Not used Not used Not used Not used Not used Not used Not used Not used Not used Not used Not used 0 = Charge normally 1 = Terminate charging 0 = Charge normally 1 = Terminate charging 0 = Charge normally 1 = Terminate charging 0 = Charge normally 1 = Terminate charging 0 = Charge normally 1 = Terminate charging DESCRIPTION
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
ChargingCurrent() (POR: 0x0080) The ChargingCurrent() command uses the Write-Word protocol (Figure 3a). The command code for ChargingCurrent() is 0x14 (0b00010100). The 16-bit binary number formed by D15-D0 represents the current-limit set point (I0) in milliamps. However, since the MAX1645 has 64mA resolution in setting I0, the D0-D5 bits are ignored as shown in Table 4. Figure 6 shows the mapping between I0 (the current-regulation-loop set point) and the ChargingCurrent() code. All codes above 0b00 1011 1100 0000 (3008mA) result in a current overrange, limiting the charger current to 3.008A. All codes below 0b0000 0000 1000 0000 (128mA) turn the charging current off. A 50m sense resistor (R2 in Figure 1) is required to achieve the correct CODE/current scaling. The power-on reset value for the ChargingCurrent() register is 0x0080; thus, the first time a MAX1645 is powered on, the BATT current regulates to 128mA. Any time the battery is removed, the ChargingCurrent() register returns to its power-on reset state. ChargingVoltage() (POR: 0x4800) The ChargingVoltage() command uses the Write-Word protocol (Figure 3a). The command code for ChargingVoltage() is 0x15 (0b00010101). The 16-bit binary number formed by D15-D0 represents the voltage set point (V0) in millivolts; however, since the MAX1645 has 16mV resolution in setting V0, the D0, D1, D2, and D3 bits are ignored as shown in Table 5. The ChargingVoltage command is used to set the battery charging voltage compliance from 1.024V to 18.432V. All codes greater than or equal to 0b0100 1000 0000 0000 (18432mV) result in a voltage overrange, limiting the charger voltage to 18.432V. All codes below 0b0000 0100 0000 0000 (1024mV) terminate charge. Figure 7 shows the mapping between V0 (the voltage-regulation-loop set point) and the ChargingVoltage() code. The power-on reset value for the ChargingVoltage() register is 0x4880; thus, the first time a MAX1645 is powered on, the BATT voltage regulates to 18.432V. Any time the battery is removed, the ChargingVoltage() register returns to its power-on reset state. The voltage at DAC corresponds to the set compliance voltage divided by 4.5. AlarmWarning() (POR: Not Alarm) The AlarmWarning() command uses the Write-Word protocol (Figure 3a). The command code for AlarmWarning() is 0x16 (0b00010110). AlarmWarning() sets the ALARM_INHIBITED status bit in the MAX1645 if D15, D14, D13, D12, or D11 of the Write-Word protocol data equals 1. Table 6 summarizes the AlarmWarning() command's function. The ALARM_INHIBITED status bit remains set until the battery is removed, a ChargerMode() command is written with the POR_RESET bit set, or new ChargingCurrent() AND ChargingVoltage() values are written. As long as ALARM_INHIBITED = 1, the MAX1645 switching regulator remains off.
MAX1645
Interrupts and Alert Response Address
The MAX1645 requests an interrupt by pulling the INT pin low. An interrupt is normally requested when there is a change in the state of the ChargerStatus() bits POWER_FAIL (bit 13), BATTERY_PRESENT (bit 14), or AC_PRESENT (bit 15). Therefore, the INT pin will pull low whenever the AC adapter is connected or disconnected, the battery is inserted or removed, or the charger goes in or out of dropout. The interrupts from each of the ChargerStatus() bits can be masked by an associated ChargerMode() bit POWER_FAIL_MASK (bit 6), BATTERY_PRESENT_MASK (bit 5), or AC_PRESENT_MASK (bit 4). All interrupts are cleared by sending any command to the MAX1645, or by sending a command to the AlertResponse() address, 0x19, using a modified Receive Byte protocol. In this protocol, all devices that set an interrupt will try to respond by transmitting their address, and the device with the highest priority, or most leading 0's, will be recognized and cleared. The process will be repeated until all devices requesting interrupts are addressed and cleared. The MAX1645 responds to the AlertResponse() address with 0x13, which is its address and a trailing "1."
150.4
AVERAGE (CSIP-CSIN) VOLTAGE IN CURRENT REGULATION (mV)
102.4
51.2
6.4
0x0080 128
0x0400 1024
0x0800 2048
0x0BC0 3008
0XFFFF 65535
Figure 6. Average Voltage Between CSIP and CSIN vs. Charging Current() Code 23
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
18.432V
16.800V
VREF = 4.096V VDCIN > 20V
12.592V
VOLTAGE SET POINT (V0)
8.400V
4.192V
1.024V
0 0 0x0400 0x106x 0x20Dx 0x313x 0x41A0 0x4800 0xFFFF
ChargingVoltage() D15-D0 DATA
Figure 7. ChargingVoltage() Code to Voltage Mapping
Charger Timeout
The MAX1645 includes a timer that terminates charge if the charger has not received a ChargingVoltage() or ChargingCurrent() command in 175sec. During charging, the timer is reset each time a ChargingVoltage() or ChargingCurrent() command is received; this ensures that the charging cycle is not terminated. If timeout occurs, charging will terminate and both ChargingVoltage() and ChargingCurrent() commands are required to restart charging. A power-on reset will also restart charging at 128mA.
DC-DC Controller The control scheme is a constant off-time, variable frequency, cycle-by-cycle current mode. The off-time is constant for a given BATT voltage; it varies with VBATT to keep the ripple current constant. During low-dropout operation, a maximum on-time of 10ms allows the controller to achieve >99% duty cycle with continuous conduction. Figure 8 shows the controller functional diagram. MOSFET Drivers The low-side driver output DLO swings from 0V to DLOV. DLOV is usually connected through a filter to LDO. The high-side driver output DHI is bootstrapped off LX and swings from VLX to VBST. When the low-side
DC-to-DC Converter
The MAX1645 employs a buck regulator with a bootstrapped NMOS high-side switch and a low-side NMOS synchronous rectifier.
24
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
10ms S BST IMAX 4.0V R Q CSSP CSS CSSN BST R CCMP CHG Q DHI DHI LX CBST R1 ADAPTER IN LDO
RESET
MAX1645
IMIN 0.25V
S
Q DLO 1s DLO L1
ZCMP 0.1V CSI
CSIP R2 CSIN LVC GMS BATT COUT GMI RFC 70k GMV DACV DACI CLS ON RFI 20k BATTERY
CONTROL
CCS
CCI
CCV
Figure 8. DC-to-DC Converter Functional Diagram
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25
Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
driver turns on, BST rises to one diode voltage below DLOV. Filter DLOV with an RC circuit whose cutoff frequency is about 50kHz. The configuration in Figure 1 introduces a cutoff frequency of around 48kHz. f = 1 / 2RC = 1 / (2 * * 33 * 0.1F) = 48kHz removing the battery or sending a POR with the ChargerMode() command. The charger is stopped unless the HOT_STOP bit is cleared in the ChargerMode() command. * THERMISTOR_UR bit is set when the thermistor value is <500 (i.e., THM is grounded). Multiple bits may be set depending on the value of the thermistor (e.g., a thermistor that is 450 will cause both the THERMISTOR_HOT and the THERMISTOR_UR bits to be set). The thermistor may be replaced by fixed-value resistors in battery packs that do not require the thermistor as a secondary fail-safe indicator. In this case, it is the responsibility of the battery pack to manipulate the resistance to obtain correct charger behavior.
Thermistor Comparators
Four thermistor comparators evaluate the voltage at the THM input to determine the battery temperature. This input is meant to be used with the internal thermistor connected to ground inside the battery pack. Connect the output of the battery thermistor to THM. Connect a resistor from THM to VDD. The resistor-divider sets the voltage at THM. When the charger is not powered up, the battery temperature can still be determined if VDD is powered from an external voltage source.
Load and Source Switch Drivers
The MAX1645 can drive two P-channel MOSFETs to eliminate voltage drops across the Schottky diodes, which are normally used to switch the load current from the battery to the main DC source: * The source switch P1 is controlled by PDS. This Pchannel MOSFET is turned on when CVS rises to 300mV above BATT and turns off when CVS falls to 100mV above BATT. The same signal that controls the PDS also sets the POWER_FAIL bit in the Charger Status() register. See Operating Conditions. * The load switch P2 is controlled by PDL. This Pchannel MOSFET is turned off when the CVS rises to 100mV below BATT and turns on when CVS falls to 300mV below BATT.
Thermistor Bits
Figure 9 shows the expected electrical behavior of a 103ETB-type thermistor (nominally 10k at +25C 5% or better) to be used with the MAX1645: * THERMISTOR_OR bit is set when the thermistor value is >100k. This indicates that the thermistor is open or a battery is not present. The charger is set to POR, and the BATTERY_PRESENT bit is cleared. * THERMISTOR_COLD bit is set when the thermistor value is >30k. The thermistor indicates a cold battery. This bit does not affect the charge. * THERMISTOR_HOT bit is set when the thermistor value is <3k. This is a latched bit and is cleared by
Dropout Operation
The MAX1645 has a 99.99% duty-cycle capability with a 10ms maximum on-time and 1s off-time. This allows the charger to achieve dropout performance limited only by resistive losses in the DC-DC converter components (P1, R1, N1, R2; see Figure 1). The actual dropout voltage is limited to 300mV between CVS and BATT by the power-fail comparator (see Operating Conditions).
1000
RESISTANCE (k)
100
10
1
0.1 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 TEMPERATURE (C)
Figure 9. Typical Thermistor Characteristics
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
VCC +12V, -12V
SYSTEM POWER SUPPLY
DC (UNREGULATED) / VBATTERY
SYSTEM POWER CONTROL AC
VBATTERY
DC (UNREGULATED)
AC-DC CONVERTER (UNREGULATED)
SYSTEM HOST (SMBus HOST)
SMART BATTERY
SAFETY SIGNAL
MAX1645 SMART BATTERY CHARGER
CRITICAL EVENTS BATTERY DATA/STATUS REQUESTS
CHARGING VOLTAGE/CURRENT REQUESTS CRITICAL EVENTS
SMBus
Figure 10. Typical Single Smart Battery System
Applications Information
Smart Battery Charging System/Background Information
A smart battery charging system, at a minimum, consists of a smart battery and smart battery charger compatible with the Smart Battery System Specifications using the SMBus. A system may use one or more smart batteries. Figure 10 shows a single-battery system. This configuration is typically found in notebook computers, video cameras, cellular phones, or other portable electronic equipment. Another configuration uses two or more smart batteries (Figure 11). The smart battery selector is used either to connect batteries to the smart battery charger or the system, or to disconnect them, as appropriate. For each battery, three connections must be made: power (the battery's positive and negative terminals), the
SMBus (clock and data), and the safety signal (resistance, typically temperature dependent). Additionally, the system host must be able to query any battery so it can display the state of all batteries present in the system. Figure 11 shows a two-battery system where battery 2 is being charged while battery 1 is powering the system. This configuration may be used to "condition" battery 1, allowing it to be fully discharged prior to recharge.
Smart Battery Charger Types
Two types of smart battery chargers are defined: Level 2 and Level 3. All smart battery chargers communicate with the smart battery using the SMBus; the two types differ in their SMBus communication mode and whether they modify the charging algorithm of the smart battery (Table 7). Level 3 smart battery chargers are supersets of Level 2 chargers and, as such, support all Level 2 charger commands.
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
VCC +12V, -12V AC SYSTEM POWER SUPPLY DC (UNREGULATED) / VBATTERY NOTE: SB 1 POWERING SYSTEM SB 2 CHARGING AC-DC CONVERTER (UNREGULATED)
SMART BATTERY 1
SMART BATTERY 2
SMBus
SAFETY
SAFETY
SIGNAL
SIGNAL
SMBus
VBATT
VBATT
SMBus SYSTEM HOST (SMBus HOST) SMART BATTERY SELECTOR SAFETY SIGNAL VCHARGE MAX1645 SMART BATTERY CHARGER
CRITICAL EVENTS BATTERY DATA/STATUS REQUESTS SMBus
Figure 11. Typical System Using Multiple Smart Batteries
Table 7. Smart Battery Charger Type by SMBus Mode and Charge Algorithm Source
CHARGE ALGORITHM SOURCE SMBus MODE Slave only Slave/Master BATTERY Level 2 Level 3 MODIFIED FROM BATTERY Level 3 Level 3
Level 2 Smart Battery Charger
The Level 2 or smart battery-controlled smart battery charger interprets the smart battery's critical warning messages and operates as an SMBus slave device to respond to the smart battery's ChargingVoltage() and ChargingCurrent() messages. The charger is obliged to adjust its output characteristics in direct response to the ChargingVoltage() and ChargingCurrent() messages it receives from the battery. In Level 2 charging, the smart battery is completely responsible for initiating the communication and providing the charging algorithm to the charger. The smart battery is in the best position to tell the smart battery charger how it needs to be charged. The charging algorithm in the battery may request a static charge condition or may choose to periodically adjust the smart battery charger's output to meet its present needs. A Level 2 smart battery charger is truly chem-
Note: Level 1 smart battery chargers were defined in the version 0.95a specification. While they can correctly interpret smart battery end-of-charge messages, minimizing overcharge, they do not provide truly chemistry-independent charging. They are no longer defined by the Smart Battery Charger Specification and are explicitly not compliant with this and subsequent Smart Battery Charger Specifications.
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
istry independent and, since it is defined as an SMBus slave device only, the smart battery charger is relatively inexpensive and easy to implement. The low-side switch N2 should also have a current rating of at least 3A, have an RDS(ON) of 100m or less, and a total gate charge less than 10nC. N2 is used to provide the starting charge to the BST capacitor C14. During normal operation, the current is carried by Schottky diode D2. Choose a 3A or higher Schottky diode. D3 is a signal-level diode, such as the 1N4148. This diode provides the supply current to the high-side MOSFET driver. The P-channel MOSFET P2 delivers the current to the load when the AC adapter is removed. Select a MOSFET with an RDS(ON) of 50m or less to minimize power loss and voltage drop.
Selecting External Components
Table 9 lists the recommended components and refers to the circuit of Figure 1; Table 8 lists the suppliers' contacts. The following sections describe how to select these components.
MOSFETs and Schottky Diodes
Schottky diode D1 provides power to the load when the AC adapter is inserted. Choose a 3A Schottky diode 3A or higher. This diode may not be necessary if P1 is used. The P-channel MOSFET P1 turns on when VCVS > VBATT. This eliminates the voltage drop and power consumption of the Schottky diode. To minimize power loss, select a MOSFET with an RDS(ON) of 50m or less. This MOSFET must be able to deliver the maximum current as set by R1. D1 and P1 provide protection from reversed voltage at the adapter input. The N-channel MOSFETs N1 and N2 are the switching devices for the buck controller. High-side switch N1 should have a current rating of at least 6A and have an RDS(ON) of 50m or less. The driver for N1 is powered by BST; its current should be less than 10mA. Select a MOSFET with a low total gate charge and determine the required drive current by IGATE = QGATE * f (where f is the DC-DC converter maximum switching frequency of 400kHz).
Inductor Selection
Inductor L1 provides power to the battery while it is being charged. It must have a saturation current of at least 3A plus 1/2 of the current ripple (IL). ISAT = 3A + 1/2 IL The controller determines the constant off-time period, which is dependent on BATT voltage. This makes the ripple current independent of input and battery voltage and should be kept to less than 1A. Calculate the IL with the following equation: IL = 16Vs / L Higher inductor values decrease the ripple current. Smaller inductor values require higher saturation current capabilities and degrade efficiency. Typically, a 22H inductor is ideal for all operating conditions.
Table 8. Components Suppliers
COMPONENT MANUFACTURER Sumida Inductor Coilcraft Coiltronics Internal Rectifier MOSFET Fairchild Vishay-Siliconix Sense Resistor Dale IRC AVX Sprague Motorola Diode Nihon Central Semiconductor PART CDRH127 series D03316P series UP2 series IRF7309 FDS series Si4435/6 WSL series LR2010-01 series TPS series, TAJ series 595D series 1N5817-1N5822 NSQ03A04 CMSH series
Other Components
CCV, CCI, and CCS are the compensation points for the three regulation loops. Bypass CCV with a 10k resistor in series with a 0.01F capacitor to GND. Bypass CCI and CCS with 0.01F capacitors to GND. R7 and R13 serve as protection resistors to THM and CVS, respectively. To achieve acceptable accuracy, R6 should be 10k and 1% to match the internal battery thermistor.
Current-Sense Input Filtering
In normal circuit operation with typical components, the current-sense signals can have high-frequency transients that exceed 0.5V due to large current changes and parasitic component inductance. To achieve proper battery and input current compliance, the currentsense input signals should be filtered to remove large common-mode transients. The input current limit sensing circuitry is the most sensitive case due to large current steps in the input filter capacitors (C1 and C2) in
29
Capacitor
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Table 9. Component Selection
DESIGNATION C1, C2 Input Capacitors C3, C4 Output Capacitors C5, C19, C20 C6, C7, C12 C8, C14, C16 C9, C10, C11 Compensation Capacitors C13 C18, C24 C23 D1, D2 D3, D4 L1 N1 High-Side MOSFET DESCRIPTION 22F, 35V low-ESR tantalum capacitors AVX TPSE226M035R0300 22F, 25V low-ESR tantalum capacitors AVX TPSD226M025R0200 1F, >30V ceramic capacitors 1F ceramic capacitors 0.1F ceramic capacitors 0.01F ceramic capacitors 1500pF ceramic capacitor 0.1F, >20V ceramic capacitors 0.1F, >30V ceramic capacitor 40V, 2A schottky diodes Central Semiconductor CMSH2-40 Small-signal diodes Central Semiconductor CMPSH-3 22H, 3.6A buck inductor Sumida CDRH127-220 30V, 11.5A, high-side N-channel MOSFET (SO-8) Fairchild FDS6680 30V, 8.4A, low-side N-channel MOSFET Fairchild FDS6612A or 30V, signal level N-channel MOSFET 2N7002 30V, 11A P-Channel MOSFET load and source switches Fairchild FDS6675 40m 1%, 0.5W battery current-sense resistor Dale WSL-2010/40m/1% 50m 1%, 0.5W source current-sense resistor Dale WSL-2010/50m/1% R3 + R4 >100k input current-limit setting resistors 10k 5% resistors 10k 1% temperature sensor network resistor 1 5% resistors 33 5% resistor 1k 5% resistor 4.7 5% resistors
N2 Low-Side MOSFET
P1, P2 R1 R2 R3, R4 R5, R7, R8, R9, R10 R6 R11, R16 R12 R13 R14, R15
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting
Figure 1. Use 1F ceramic capacitors from CSSP and CSSN to GND. Smaller 0.1F ceramic capacitors can be used on the CSIP and CSIN inputs to GND since the current into the battery is continuous. Place these capacitors next to the single-point ground directly under the MAX1645. The resulting top-layer subground plane is connected to the normal inner-layer ground plane at the output ground terminals, which ensures that the IC's analog ground is sensing at the supply's output terminals without interference from IR drops and ground noise. Other highcurrent paths should also be minimized, but focusing primarily on short ground and currentsense connections eliminates about 90% of all PC board layout problems. 2) Place the IC and signal components. Keep the main switching nodes (LX nodes) away from sensitive analog components (current-sense traces and REF capacitor). Important: The IC must be no further than 10mm from the current-sense resistors. Keep the gate drive traces (DHI, DLO, and BST) shorter than 20mm and route them away from the current-sense lines and REF. Place ceramic bypass capacitors close to the IC. The bulk capacitors can be placed further away. Place the current-sense input filter capacitors under the part, connected directly to the GND pin. 3) Use a single-point star ground placed directly below the part. Connect the input ground trace, power ground (subground plane), and normal ground to this node.
MAX1645
Layout and Bypassing
Bypass DCIN with a 1F to GND (Figure 1). D4 protects the device when the DC power source input is reversed. A signal diode for D4 is adequate as DCIN only powers the LDO and the internal reference. Bypass LDO, BST, DLOV, and other pins as shown in Figure 1. Good PC board layout is required to achieve specified noise, efficiency, and stable performance. The PC board layout artist must be given explicit instructions, preferably a pencil sketch showing the placement of power-switching components and high-current routing. Refer to the PC board layout in the MAX1645 evaluation kit manual for examples. A ground plane is essential for optimum performance. In most applications, the circuit will be located on a multilayer board, and full use of the four or more copper layers is recommended. Use the top layer for high-current connections, the bottom layer for quiet connections (REF, CCV, CCI, CCS, DAC, DCIN, VDD, and GND), and the inner layers for an uninterrupted ground plane. Use the following step-by-step guide: 1) Place the high-power connections first, with their grounds adjacent: * Minimize current-sense resistor trace lengths and ensure accurate current sensing with Kelvin connections. * Minimize ground trace lengths in the high-current paths. * Minimize other trace lengths in the high-current paths: * Use > 5mm-wide traces * Connect C1 and C2 to high-side MOSFET (10mm max length) * Connect rectifier diode cathode to low-side. MOSFET (5mm max length) * LX node (MOSFETs, rectifier cathode, inductor: 15mm max length). Ideally, surface-mount power components are flush against one another with their ground terminals almost touching. These high-current grounds are then connected to each other with a wide, filled zone of toplayer copper so they do not go through vias.
Chip Information
TRANSISTOR COUNT: 6996
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Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645
Typical Operating Circuit
ADAPTER IN
CVS DCIN
DDS CSSP MAX1645
REF
CSSN LDO LOAD
CLS BST DLOV DAC CCV DHI CCI LX
AGND
CCS DLO PGND
CSIP
CSIN PDL BATT BATTERY THM VDD HOST
SCL SDA INT
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.
32 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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