19-2593; Rev 0; 10/02 Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting Features ♦ Input Current Limiting The MAX1645B employs a next-generation synchronous buck control circuitry that lowers the minimum input-to-output voltage drop by allowing the duty cycle to exceed 99%. The MAX1645B can easily charge one to four series Li+ cells. ♦ +8V to +28V Input Voltage Range Applications ♦ 175s Charge Safety Timeout ♦ 128mA Wake-Up Charge ♦ Charges Any Chemistry Battery: Li+, NiCd, NiMH, Lead Acid, etc. ♦ Intel SMBus 2-Wire Serial Interface ♦ Compliant with Level 2 Smart Battery Charger Spec Rev 1.0 ♦ Up to 18.4V Battery Voltage ♦ 11-Bit Battery Voltage Setting ♦ ±0.8% Output Voltage Accuracy with Internal Reference ♦ 3A (max) Battery Charge Current Notebook Computers ♦ 6-Bit Charge-Current Setting Point-of-Sale Terminals ♦ 99.99% (max) Duty Cycle for Low-Dropout Operation Personal Digital Assistants ♦ Load/Source Switchover Drivers ♦ >97% Efficiency Pin Configuration TOP VIEW Ordering Information PART DCIN 1 28 CVS LDO 2 27 PDS CLS 3 26 CSSP REF 4 25 CSSN CCS 5 CCI 6 MAX1645BEEI TEMP RANGE -40°C to +125°C PIN-PACKAGE 28 QSOP 24 BST MAX1645B 23 DHI CCV 7 22 LX GND 8 21 DLOV BATT 9 20 DLO DAC 10 19 PGND VDD 11 18 CSIP THM 12 17 CSIN SCL 13 16 PDL SDA 14 15 INT QSOP Typical Operating Circuit appears at end of data sheet. SMBus is a trademark of Intel Corp. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX1645B General Description The MAX1645B 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 MAX1645B automatically transitions from regulating current to regulating voltage. The MAX1645B can also limit line input current so as not to exceed a predetermined current drawn from the DC source. A 175s charge safety timer prevents “runaway charging” should the MAX1645B stop receiving charging voltage/current commands. MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting ABSOLUTE MAXIMUM RATINGS 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 = +70°C) 28-Pin QSOP (derate 10.8mW/°C above +70°C).........860mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-60°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C 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) 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 = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 28 V GENERAL SPECIFICATIONS DCIN Typical Operating Range VDCIN DCIN Supply Current IDCIN 8 8V < VDCIN < 28V 1.7 6 mA DCIN Supply Current Charging Inhibited 8V < VDCIN < 28V 0.7 2 mA DCIN Undervoltage Threshold When AC_PRESENT switches 7.5 7.85 LDO Output Voltage DCIN falling 7 7.4 5.4 8V < VDCIN < 28V, 0 < ILDO < 15mA 5.15 VDD Input Voltage Range 8V < VDCIN < 28V (Note 1) 2.80 VDD Undervoltage Threshold When the SMB responds to commands VDD Quiescent Current REF Output Voltage VLDO DCIN rising IDD VREF BATT Undervoltage Threshold VDD rising VDD falling 2.55 2.1 0 < VDCIN < 6V, VDD = 5V, VSCL = 5V, VSDA = 5V 0 < IREF < 200µA 4.066 When ICHARGE drops to 128mA (Note 2) 2.4 V 5.65 V 5.65 V 2.8 2.5 V 80 150 µA 4.096 4.126 V 2.8 V PDS Charging Source Switch Turn-Off Threshold VPDS-OFF VCVS referred to VBATT, VCVS falling 50 100 150 mV PDS Charging Source Switch Threshold Hysteresis VPDS-HYS VCVS referred to VBATT 100 200 300 mV 8 10 12 V 300 µA PDS Output Low Voltage, PDS Below CSSP IPDS = 0 PDS Turn-On Current PDS = CSSP 100 150 PDS Turn-Off Current VPDS = VCSSP - 2V, VDCIN = 16V 10 50 -150 -100 PDL Load Switch Turn-Off Threshold 2 VPDL-OFF VCVS referred to VBATT, VCVS rising _______________________________________________________________________________________ mA -50 mV Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting (Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER PDL Load Switch Threshold Hysteresis SYMBOL VPDL-HYS CONDITIONS VCVS referred to VBATT MIN TYP MAX UNITS 100 200 300 mV PDL Turn-Off Current VCSSN - VPDL = 1V 6 12 PDL Turn-On Resistance PDL to GND 50 100 150 kΩ CVS Input Bias Current VCVS = 28V 6 20 µA BATT Full-Charge Voltage BATT Charge Current-Sense Voltage V0 ChargingVoltage() = 0x41A0 16.666 16.8 16.934 ChargingVoltage() = 0x3130 12.492 12.592 12.692 ChargingVoltage() = 0x20D0 8.333 8.4 8.467 ChargingVoltage() = 0x1060 4.150 4.192 4.234 139.9 150.4 160.9 ChargingCurrent() = 0x0BC0 I0 mA VCSIP - VCSIN DCIN Source Current-Limit Sense Voltage VCSSP - VCSSN BATT Undervoltage Charge Current-Sense Voltage VCSIP - VCSIN Inductor Peak Current Limit VCSIP - VCSIN V mV ChargingCurrent() = 0x0080 3.08 VCLS = 4.096V 188.6 204.8 221.0 VCLS = 2.048V 91.3 102.4 113.5 VBATT = 1V 3.08 6.4 9.72 mV 250 300 350 mV 0 20 V BATT/CSIP/CSIN Input Voltage Range 6.4 9.72 mV Total BATT Input Bias Current Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V -700 +700 µA Total BATT Quiescent Current Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V, charge inhibited -100 +100 µA Total BATT Standby Current Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V, VDCIN = 0 -5 +5 µA CSSP Input Bias Current VCSSP = VCSSN = VDCIN = 0 to 28V -100 540 +1000 µA CSSN Input Bias Current VCSSP = CCSSN = VDCIN = 0 to 28V -100 35 +100 µA CSSP/CSSN Quiescent Current VCSSP = VCSSN = 28V, VDCIN = 0 +1 µA Battery Voltage-Error Amp DC Gain From BATT to CCV CLS Input Bias Current VCLS = VREF/2 to VREF Battery Voltage-Error Amp Transconductance From BATT to CCV, ChargingVoltage() = 0x41A0, VBATT = 16.8V Battery Current-Error Amp Transconductance -1 200 500 V/V -1 +0.05 +1 µA 0.111 0.222 0.444 µA/mV From CSIP/CSIN to CCI, ChargingCurrent() = 0x0BC0, VCSIP - VCSIN = 150.4mV 0.5 1 2.0 µA/mV Input Current-Error Amp Transconductance From CSSP/CSSN to CCS, VCLS = 2.048V, VCSSP - VCSSN = 102.4mV 0.5 1 2.0 µA/mV CCV/CCI/CCS Clamp Voltage VCCV = VCCI = VCCS = 0.25V to 2V (Note 3) 150 300 600 mV _______________________________________________________________________________________ 3 MAX1645B ELECTRICAL CHARACTERISTICS (continued) MAX1645B 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 = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC-TO-DC CONVERTER SPECIFICATIONS Minimum Off-Time tOFF 1.0 1.25 1.5 µs Maximum On-Time tON 5 10 15 ms 99 99.99 500 µA 1 µA Maximum Duty Cycle LX Input Bias Current VDCIN = 28V, VBATT = VLX = 20V LX Input Quiescent Current VDCIN = 0, VBATT = VLX = 20V 200 % BST Supply Current DHI high 6 15 µA DLOV Supply Current VDLOV = VLDO, DLO low 5 10 µA DHI Output Resistance DHI high or low, VBST - VLX = 4.5V 6 14 Ω DLO Output Resistance DLO high or low, VDLOV = 4.5V 6 14 Ω +1 µA THERMISTOR COMPARATOR SPECIFICATIONS THM Input Bias Current VTHM = 4% of VDD to 96% of VDD, VDD = 2.8V to 5.65V Thermistor Overrange Threshold VDD = 2.8V to 5.65V, VTHM falling 89.5 91 92.5 % of VDD Thermistor Cold Threshold VDD = 2.8V to 5.65V, VTHM falling 74 75.5 77 % of VDD Thermistor Hot Threshold VDD = 2.8V to 5.65V, VTHM falling 22 23.5 25 % of VDD Thermistor Underrange Threshold VDD = 2.8V to 5.65V, VTHM falling 6 7.5 9 % of VDD Thermistor Comparator Threshold Hysteresis All four comparators, VDD = 2.8V to 5.65V -1 1 % of VDD SMB INTERFACE LEVEL SPECIFICATIONS (VDD = 2.8V to 5.65V) SDA/SCL Input Low Voltage 0.6 SDA/SCL Input High Voltage 1.4 SDA/SCL Input Hysteresis V 220 SDA/SCL Input Bias Current -1 SDA Output Low Sink Current VSDA = 0.4V INT Output High Leakage V I NT = 5.65V INT Output Low Voltage I I NT = 1mA V mV +1 6 µA mA 25 1 µA 200 mV SMB INTERFACE TIMING SPECIFICATIONS (VDD = 2.8V to 5.65V, Figures 4 and 5) SCL High Period tHIGH 4 µs SCL Low Period tLOW 4.7 µs Start Condition Setup Time from SCL tSU:STA 4.7 µs Start Condition Hold Time from SCL tHD:STA 4 µs SDA Setup Time from SCL tSU:DAT 250 ns SDA Hold Time from SCL tHD:DAT 0 ns 4 _______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting (Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL SDA Output Data Valid from SCL tDV Maximum Charge Period Without a ChargingVoltage() or Charging Current() Loaded tWDT CONDITIONS MIN 140 TYP 175 MAX UNITS 1 µs 210 s ELECTRICAL CHARACTERISTICS (Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = -40°C to +85°C, unless otherwise noted. Guaranteed by design.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 28 V GENERAL SPECIFICATIONS DCIN Typical Operating Range VDCIN DCIN Supply Current IDCIN 8 8V < VDCIN < 28V 6 mA DCIN Supply Current Charging Inhibited 8V < VDCIN < 28V 2 mA DCIN Undervoltage Threshold When AC_PRESENT switches LDO Output Voltage VLDO DCIN rising DCIN falling 7.85 7 V 8V < VDCIN < 28V, 0 < ILDO < 15mA 5.15 5.65 V VDD Input Voltage Range 8V < VDCIN < 28V (Note 1) 2.80 5.65 V VDD Undervoltage Threshold When the SMB responds to commands VDD Quiescent Current REF Output Voltage IDD VREF BATT Undervoltage Threshold VDD rising VDD falling 2.8 2.1 0 < VDCIN < 6V, VDD = 5V, VSCL = 5V, VSDA = 5V 0 < IREF < 200µA V 150 µA 4.035 4.157 V When ICHARGE drops to 128mA (Note 2) 2.4 2.8 V PDS Charging Source Switch Turn-Off Threshold VPDS-OFF VCVS referred to VBATT, VCVS falling 50 150 mV PDS Charging Source Switch Threshold Hysteresis VPDS-HYS VCVS referred to VBATT 100 300 mV 8 12 V 300 PDS Output Low Voltage, PDS Below CSSP IPDS = 0 PDS Turn-On Current PDS = CSSP 100 PDS Turn-Off Current VPDS = VCSSP - 2V, VDCIN = 16V 10 µA mA PDL Load Switch Turn-Off Threshold VPDL-OFF VCVS referred to VBATT, VCVS rising -150 -50 mV PDL Load Switch Threshold Hysteresis VPDL-HYS VCVS referred to VBATT 100 300 mV PDL Turn-Off Current VCSSN - VPDL = 1V 6 mA _______________________________________________________________________________________ 5 MAX1645B ELECTRICAL CHARACTERISTICS (continued) MAX1645B 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 = -40°C to +85°C, unless otherwise noted. Guaranteed by design.) PARAMETER SYMBOL CONDITIONS PDL Turn-On Resistance PDL to GND CVS Input Bias Current VCVS = 28V MIN TYP 50 MAX UNITS 150 kΩ 20 µA ERROR AMPLIFIER SPECIFICATIONS BATT Full-Charge Voltage BATT Charge Current-Sense Voltage V0 I0 ChargingVoltage() = 0x41A0 16.532 17.068 ChargingVoltage() = 0x3130 12.391 12.793 ChargingVoltage() = 0x20D0 8.266 8.534 ChargingVoltage() = 0x1060 4.124 4.260 ChargingCurrent() = 0x0BC0 130.4 170.4 ChargingCurrent() = 0x0080 0.76 12.04 VCLS = 4.096V 174.3 235.3 VCLS = 2.048V 82.2 120.2 1 10 mV 250 350 mV 0 20 V VCSIP - VCSIN V mV DCIN Source Current-Limit Sense Voltage VCSSP - VCSSN BATT Undervoltage Charge Current-Sense Voltage VBATT = 1V, VCSIP - VCSIN Inductor Peak Current Limit VCSIP - VCSIN BATT/CSIP/CSIN Input Voltage Range mV Total BATT Input Bias Current Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V -700 +700 µA Total BATT Quiescent Current Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V, charge inhibited -100 +100 µA Total BATT Standby Current Total of IBATT, ICSIP, and ICSIN; VBATT = 0 to 20V, VDCIN = 0 -5 +5 µA CSSP/Input Bias Current VCSSP = VCSSN = VDCIN = 0 to 28V -100 +1000 µA CSSN Input Bias Current VCSSP = CCSSN = VDCIN = 0 to 28V -100 +100 mA CSSP/CSSN Quiescent Current VCSSP = VCSSN = 28V, VDCIN = 0 -1 +1 µA Battery Voltage-Error Amp DC Gain From BATT to CCV CLS Input Bias Current VCLS = VREF/2 to VREF Battery Voltage-Error Amp Transconductance From BATT to CCV, ChargingVoltage() = 0x41A0, VBATT = 16.8V Battery Current-Error Amp Transconductance 200 V/V -1 +1 µA 0.111 0.444 µA/mV From CSIP/CSIN to CCI, ChargingCurrent() = 0x0BC0, VCSIP - VCSIN = 150.4mV 0.5 2.0 µA/mV Input Current-Error Amp Transconductance From CSSP/CSSN to CCS, VCLS = 2.048V, VCSSP - VCSSN = 102.4mV 0.5 2.0 µA/mV CCV/CCI/CCS Clamp Voltage VCCV = VCCI = VCCS = 0.25V to 2V (Note 3) 150 600 mV 6 _______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting (Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = -40°C to +85°C, unless otherwise noted. Guaranteed by design.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC-TO-DC CONVERTER SPECIFICATIONS Minimum Off-Time tOFF 1.0 1.5 µs Maximum On-Time tON 5 15 ms Maximum Duty Cycle 99 % LX Input Bias Current VDCIN = 28V, VBATT = VLX = 20V 500 µA LX Input Quiescent Current VDCIN = 0, VBATT = VLX = 20V 1 µA BST Supply Current DHI high 15 µA DLOV Supply Current VDLOV = VLDO, DLO low 10 µA DHI Output Resistance DHI high or low, VBST - VLX = 4.5V 14 Ω DLO Output Resistance DLO high or low, VDLOV = 4.5V 14 Ω THERMISTOR COMPARATOR SPECIFICATIONS THM Input Bias Current VTHM = 4% of VDD to 96% of VDD, VDD = 2.8V to 5.65V -1 +1 µA Thermistor Overrange Threshold VDD = 2.8V to 5.65V, VTHM falling 89.5 92.5 % of VDD Thermistor Cold Threshold VDD = 2.8V to 5.65V, VTHM falling 74 77 % of VDD Thermistor Hot Threshold VDD = 2.8V to 5.65V, VTHM falling 22 25 % of VDD Thermistor Underrange Threshold VDD = 2.8V to 5.65V, VTHM falling 6 9 % of VDD 0.6 V +1 µA SMB INTERFACE LEVEL SPECIFICATIONS (VDD = 2.8V to 5.65V) SDA/SCL Input Low Voltage SDA/SCL Input High Voltage 1.4 SDA/SCL Input Bias Current -1 SDA Output Low Sink Current VSDA = 0.4V INT Output High Leakage V I NT = 5.65V INT Output Low Voltage I I NT = 1mA V 6 mA 1 µA 200 mV SMB INTERFACE TIMING SPECIFICATIONS (VDD = 2.8V to 5.65V, Figures 4 and 5) SCL High Period tHIGH 4 µs SCL Low Period tLOW 4.7 µs Start Condition Setup Time from SCL tSU:STA 4.7 µs Start Condition Hold Time from SCL tHD:STA 4 µs SDA Setup Time from SCL tSU:DAT 250 ns SDA Hold Time from SCL tHD:DAT 0 ns _______________________________________________________________________________________ 7 MAX1645B ELECTRICAL CHARACTERISTICS (continued) ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDD = +3.3V, VBATT = +16.8V, VDCIN = +18V, TA = -40°C to +85°C, unless otherwise noted. Guaranteed by design.) PARAMETER SYMBOL SDA Output Data Valid from SCL tDV Maximum Charge Period Without a ChargingVoltage() or Charging Current() Loaded tWDT CONDITIONS MIN TYP 140 MAX UNITS 1 µs 210 s Note 1: Guaranteed by meeting the SMB timing specs. Note 2: The charger reverts to a trickle-charge mode of ICHARGE = 128mA below this threshold. Note 3: 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 = +25°C, unless otherwise noted.) LOAD-TRANSIENT RESPONSE (STEP-IN LOAD CURRENT) 15V 1.25V VCCV/VCCI CCI CCI 0 CCI CCV 0.75V CCS CCI CCI 5.55 15.0V 5.50 2.75V 5.45 2.25V 5.30 CCS 0.75V 5.25 BATTERY INSERTED 5.20 400µs/div ChargingCurrent() = 3.0A 0 TO 2A LOAD STEP, VBATT = 20V ISOURCE LIMIT = 2.5A 2ms/div ChargingVoltage() = 16000mV ChargingCurrent() = 1000mA 10 15 20 25 30 VDCIN (V) REFERENCE VOLTAGE vs. TEMPERATURE 4.110 MAX1645B toc05 4.100 MAX1645B toc04 5.55 5 REFERENCE VOLTAGE LOAD REGULATION LDO LOAD REGULATION 5.60 5.40 5.35 1.75V CCI 0.25V BATTERY REMOVED 15.5V ILOAD = 0 4.098 MAX1645B toc06 CCV VCCS/VCCI IBATT 1A CCS 5.60 VLDO (V) VBATT VBATT 16V CCV LDO LINE REGULATION MAX1645B toc02 MAX1645B toc01 MAX1645B toc03 BATTERY REMOVAL AND REINSERTION TRANSIENT RESPONSE 4.105 5.50 4.100 5.40 4.096 VREF (V) 5.45 VREF (V) VLDO (V) MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting 5.35 4.090 5.30 4.092 4.085 5.25 4.090 5.20 0 2 4 6 8 10 12 14 16 18 20 LOAD CURRENT (mA) 8 4.095 4.094 0 50 100 150 200 LOAD CURRENT (µA) 250 300 4.080 -40 -20 0 20 40 60 TEMPERATURE (°C) _______________________________________________________________________________________ 80 100 Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting 80 75 70 85 80 75 70 65 60 60 A: VDCIN = 20V, ChargingVoltage() = 16.8V B: VDCIN = 16V, ChargingVoltage() = 8.4V 500 1000 1500 2000 2500 50 3000 0 BATTERY CURRENT (mA) 500 1000 1500 1.0 ChargingVoltage() = 16800mV ChargingCurrent() = 3008mA 10 2000 2500 0 3000 500 1000 1500 2000 2500 3000 3500 LOAD CURRENT (mA) ChargingCurrent() (CODE) BATT VOLTAGE ERROR vs. ChargingVoltage() CODE CURRENT-SETTING ERROR vs. ChargingCurrent() CODE 0.1 0 -0.1 MAX1645B toc11 0.2 5 4 BATT CURRENT ERROR (%) MAX1645B toc10 0.3 BATT VOLTAGE ERROR (%) 0.1 3 2 1 0 -1 -2 -3 -0.2 IBATT = 0 MEASURED AT AVAILABLE CODES VBATT = 12.6V MEASURED AT AVAILABLE CODES -4 -0.3 -5 0 4000 8000 12,000 16,000 20,000 0 500 1000 1500 2000 2500 ChargingVoltage() (CODE) ChargingCurrent() (CODE) SOURCE/BATT CURRENT vs. LOAD CURRENT WITH SOURCE CURRENT LIMIT SOURCE/BATT CURRENT vs. VBATT WITH SOURCE CURRENT LIMIT 3.0 IIN 2.5 2.0 1.5 VCLS = 2V RCSS = 40mΩ VBATT = 16.8V SOURCE CURRENT LIMIT = 2.5A ChargingCurrent() = 3008mA ChargingVoltage() = 18432mV 1.0 0.5 IBATT 3.5 3.0 SOURCE/BATT CURRENT (A) 3.5 IIN 2.5 2.0 1.5 ILOAD = 2A VCLS = 2V RCSS = 40mΩ ChargingVoltage() = 18432mV ChargingCurrent() = 3008mA SOURCE CURRENT LIMIT = 2.5A 1.0 0.5 0 3000 MAX1645B toc13 0 MAX1645B toc12 50 0.01 A: VDCIN = 20V, VBATT = 16.8V B: VDCIN = 16V, VBATT = 8.4V 55 MAX1645B toc09 90 65 55 A B 95 EFFICIENCY (%) 85 SOURCE/BATT CURRENT (A) EFFICIENCY (%) 90 0.001 MAX1645B toc08 A B 95 OUTPUT VI CHARACTERISTICS 100 MAX1645B toc07 100 EFFICIENCY vs. BATTERY CURRENT (CURRENT-CONTROL LOOP) DROP IN BATT OUTPUT VOLTAGE (%) EFFICIENCY vs. BATTERY CURRENT (VOLTAGE-CONTROL LOOP) IBATT 0 0 0.5 1.0 1.5 LOAD CURRENT (A) 2.0 2.5 0 2 4 6 8 10 12 14 16 18 20 VBATT (V) _______________________________________________________________________________________ 9 MAX1645B Typical Operating Characteristics (continued) (Circuit of Figure 1, VDCIN = 20V, TA = +25°C, unless otherwise noted.) Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645B Pin Description 10 PIN NAME 1 DCIN FUNCTION 2 LDO 5.4V Linear-Regulator Voltage Output. Bypass with a 1µF capacitor to GND. 3 CLS Source Current-Limit Input 4 REF 4.096V Reference Voltage Output 5 CCS Charging Source Compensation Capacitor Connection. Connect a 0.01µF capacitor from CCS to GND. 6 CCI Battery Current-Loop Compensation Capacitor Connection. Connect a 0.01µF capacitor from CCI to GND. 7 CCV Battery Voltage-Loop Compensation Capacitor Connection. Connect a 10kΩ resistor in series with a 0.01µF capacitor to GND. 8 GND Ground 9 BATT Battery Voltage Output 10 DAC DAC Voltage Output 11 VDD Logic Circuitry Supply Voltage Input (2.8V to 5.65V) 12 THM Thermistor Voltage Input 13 SCL SMB Clock Input 14 SDA SMB Data Input/Output. Open-drain output. Needs external pullup. 15 INT Interrupt Output. Open-drain output. Needs external pullup. DC Supply Voltage Input 16 PDL PMOS Load Switch Driver Output 17 CSIN Battery Current-Sense Negative Input 18 CSIP Battery Current-Sense Positive Input 19 PGND Power Ground 20 DLO 21 DLOV Low-Side NMOS Driver Output 22 LX Inductor Voltage Sense Input 23 DHI High-Side NMOS Driver Output 24 BST High-Side Driver Bootstrap Voltage Input. Bypass with 0.1µF capacitor to LX. 25 CSSN 26 CSSP Charging Source Current-Sense Positive Input 27 PDS Charging Source PMOS Switch Driver Output 28 CVS Charging Source Voltage Input Low-Side NMOS Driver Supply Voltage. Bypass with 0.1µF capacitor to GND. Charging Source Current-Sense Negative Input ______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting The MAX1645B 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 MAX1645B features a voltageregulation loop and two current-regulation loops. The loops operate independently of each other. The voltageregulation 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. Setting Output Voltage The MAX1645B 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 MAX1645B ignores the first 4 LSBs and uses the next 11 LSBs to control the voltage DAC. All codes greater than or equal to 0x4800 (18432mV) result in a voltage overrange, limiting the charger voltage to 18.432V. All codes below 0x0400 (1024mV) terminate charging. Setting the Charge Current The MAX1645B charge-current DAC has a 3.2mV to 150.4mV range. The SMBus specification allows for a 16-bit ChargingCurrent() command that translates to a 0.05mV LSB and a 3.376V full-scale current-sense voltage. The MAX1645B drops the first 6 LSBs and uses the remaining 6 MSBs to control the charge-current DAC. All codes above 0x0BC0 result in an overrange condition, limiting the charge current-sense voltage to 150.4mV. All codes below 0x0080 turn off the charging current. Therefore, the charging current (ICHARGE) is determined by: ICHARGE = VDACI / RCSI where V DACI is the current-sense voltage set by ChargingCurrent(), and R CSI is the battery currentsense resistor (R2 in Figure 1). When using a 50mΩ current-sense resistor, the ChargingCurrent() value corresponds directly to the charging current in milliamps (0x0400 = 1024mA = 52.2mV/50mΩ). Input Current Limiting The MAX1645B 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 loaded down. An internal amplifier, CSS, compares the voltage between CSSP and CSSN to the voltage at CLS/20. VCLS 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 ✕ η)] where η 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) / 0.04Ω = 2.56A LDO Regulator An integrated LDO regulator provides a +5.4V supply derived from DCIN, which 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. Also see the MOSFET Drivers section. The LDO also supplies the 4.096V reference and most of the control circuitry. Bypass LDO with a 1µF capacitor. 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 MAX1645B active while the supply to DCIN is removed, connect an external supply to VDD. ______________________________________________________________________________________ 11 MAX1645B Detailed Description MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting ADAPTER IN R13 1kΩ D4 1N4148 P1 FDS6675 PDS CVS DCIN C23 0.1µF C5 1µF CSSP C20, 1µF REF R3 100kΩ C7 1µF D1 1N5821 R14 4.7Ω C19, 1µF MAX1645B CSSN LDO R15 4.7Ω LOAD C6 1µF CLS R4 100kΩ GND C2 22µF C1 22µF R1 0.04Ω D3 CMPSH3 R12 33Ω BST DLOV DAC C8 0.1µF C16 0.22µF CCV R17 10kΩ R5 10kΩ C9 0.01µF DHI CCI N1 FDS6680 C14 0.1µF LX C10 1nF R18 10kΩ CCS C11 1nF DLO N2 FDS6612A L1 22µH D2 1N5821 PGND R11 1Ω CSIP C18 0.1µF C24 0.1µF R2 0.05Ω R16 1Ω CSIN PDL P2 FDS6675 C4 22µF BATT R7 10kΩ THM R6 10kΩ BATTERY C13 1.5nF HOST VDD C12 1µF R10 10kΩ R8 R9 10kΩ 10kΩ SCL SDA INT Figure 1. Typical Application Circuit 12 ______________________________________________________________________________________ C3 22µF Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645B BST MAX1645B CSSP DHI DHI CSS LX GMS CSSN DC-DC LVC CLS DLOV DLO CSIP CSI PGND GMI CSIN DLO BATT CCS CCI CCV GMV CVS BATT PDL PDS PDS PDL DCIN VDD SCL VL LDO REF REF SDA DACI INT SMB DACV GND TEMP THM DAC Figure 2. Functional Diagram ______________________________________________________________________________________ 13 MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting Operating Conditions The MAX1645B 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 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 part is in the power-fail state, since the charger does not 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 MAX1645B 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 registers are reset. With no battery present, the charger performs a “float” charge to minimize contact arcing on battery connection. The “float” charge still tries to regulate the BATT pin voltage at 18.32V 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 does not respond to commands. Coming out of the undervoltage condition, the part is in its PowerOn Reset state. No charging occurs when VDD is under voltage. SMBus Interface The MAX1645B 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. 14 The MAX1645B 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 MAX1645B is an SMBus slave 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 this part 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 MAX1645B’s 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 MAX1645B complies with Level 2 Smart Battery Charger Specification Revision 1.0; therefore, the ChargerSpecInfo() command returns 0x09. 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 ChargerMode() 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 ChargerStatus() 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. ______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting 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. a) Write-Word Format S SLAVE ADDRESS W ACK COMMAND BYTE ACK LOW DATA BYTE ACK HIGH DATA BYTE ACK 7 bits 1b 1b 8 bits 1b 8 bits 1b 8 bits 1b MSB LSB 0 0 MSB LSB 0 MSB LSB 0 MSB LSB 0 ChargerMode() = 0x12 ChargingCurrent() = 0x14 ChargerVoltage() = 0x15 AlarmWarning() = 0x16 Preset to 0b0001001 D7 D0 D15 P D8 b) Read-Word Format S SLAVE W ACK ADDRESS 7 bits 1b 1b MSB LSB 0 0 Preset to 0b0001001 COMMAND BYTE ACK S SLAVE ADDRESS R ACK LOW DATA BYTE ACK HIGH DATA BYTE 1b 8 bits 0 MSB LSB 8 bits 1b 7 bits 1b 1b 8 bits MSB LSB 0 MSB LSB 1 0 MSB LSB ChargerSpecInfo() = 0x11 ChargerStatus() = 0x13 Legend: S = Start Condition or Repeated Start Condition ACK = Acknowledge (logic low) W = Write Bit (logic low) Preset to 0b0001001 D7 D0 D15 NACK P 1b 1 D8 P = Stop Condition NACK = NOT Acknowledge (logic high) R = Read Bit (logic high) MASTER TO SLAVE SLAVE TO MASTER Figure 3. SMBus Write-Word and Read-Word Protocols ______________________________________________________________________________________ 15 MAX1645B The ChargerStatus() command returns information about thermistor impedance and the MAX1645B’s internal state. The latched bits, THERMISTOR_HOT and ALARM_INHIBITED, are cleared whenever BATTERY_ MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting START CONDITION MOST SIGNIFICANT ADDRESS BIT (A6) CLOCKED INTO SLAVE A5 CLOCKED INTO SLAVE A4 CLOCKED INTO SLAVE A3 CLOCKED INTO SLAVE SCL tHIGH tLOW tHD:STA SDA tSU:STA tSU:DAT tHD:DAT tSU:DAT tHD:DAT Figure 4. SMBus Serial Interface Timing—Address MOST SIGNIFICANT BIT OF DATA CLOCKED INTO MASTER ACKNOWLEDGE BIT CLOCKED INTO MASTER R/W BIT CLOCKED INTO SLAVE SCL SLAVE PULLING SDA LOW SDA tDV tDV Figure 5. SMBus Serial Interface Timing—Acknowledgment 16 ______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645B Table 1. ChargerSpecInfo()* BIT NAME 0 CHARGER_SPEC Returns a 1 for version 1.0 DESCRIPTION 1 CHARGER_SPEC Returns a zero for version 1.0 2 CHARGER_SPEC Returns a zero for version 1.0 3 CHARGER_SPEC Returns a 1 for version 1.0 4 SELECTOR_SUPPORT 5 Reserved Returns a zero 6 Reserved Returns a zero 7 Reserved Returns a zero 8 Reserved Returns a zero Returns a zero, indicating no smart battery selector functionality 9 Reserved Returns a zero 10 Reserved Returns a zero 11 Reserved Returns a zero 12 Reserved Returns a zero 13 Reserved Returns a zero 14 Reserved Returns a zero 15 Reserved Returns a zero *Command: 0x11 ______________________________________________________________________________________ 17 MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting Table 2. ChargerMode()* BIT NAME FUNCTION 0 INHIBIT_CHARGE 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. 1 ENABLE_POLLING Not implemented. 2 POR_RESET 3 RESET_TO_ZERO 0 = No change. 1 = Change the ChargingVoltage() to 0xFFFF and the ChargingCurrent() to 0x00C0; clear the THERMISTOR_HOT and ALARM_INHIBITED flip-flops. Not implemented. 0* = Interrupt on either edge of the AC_PRESENT status bit. 1 = Do not interrupt because of an AC_PRESENT bit change. 4 AC_PRESENT_MASK 5 BATTERY_PRESENT_ MASK 6 POWER_FAIL_MASK 7 — Not implemented. 8 — Not implemented. 9 — Not implemented. 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. 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. 10 HOT_STOP 11 — Not implemented. 12 — Not implemented. 13 — Not implemented. 14 — Not implemented. 15 — Not implemented. *Command: 0x12 *State at chip initial power-on (i.e., VDD from 0 to +3.3V). 18 ______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting BIT NAME 0 CHARGE_INHIBITED MAX1645B Table 3. ChargerStatus()* 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. 1 MASTER_MODE 2 VOLTAGE_NOT_REG Always returns zero. 3 CURRENT_NOT_REG 4 LEVEL_2 Always returns a 1. 5 LEVEL_3 Always returns a zero. 6 CURRENT_OR 0** = The ChargingCurrent() value is valid for the MAX1645B. 1 = The ChargingCurrent() value exceeds the MAX1645B output range, i.e., programmed ChargingCurrent() exceeds 3008mA. 7 VOLTAGE_OR 0 = The ChargingVoltage() value is valid for the MAX1645B. 1** = The ChargingVoltage() value exceeds the MAX1645B output range, i.e., programmed ChargingVoltage() exceeds 1843mV. 8 THERMISTOR_OR 9 THERMISTOR_COLD Function disabled. Always returns zero. Function disabled. Always returns zero. 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. 10 THERMISTOR_HOT 11 THERMISTOR_UR 0 = THM is >7.5% of the reference voltage. 1 = THM is <7.5% of the reference voltage. 12 ALARM_INHIBITED 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. 13 POWER_FAIL 14 BATTERY_PRESENT 15 AC_PRESENT 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. *Command: 0x13 **State at chip initial power-on. ______________________________________________________________________________________ 19 Table 4. ChargingCurrent()* BIT NAME 0 — Not used. Normally a 0.05mV (1mA x 50mΩ) weight. 1 — Not used. Normally a 0.1mV (2mA x 50mΩ) weight. 2 — Not used. Normally a 0.2mV (4mA x 50mΩ) weight. 3 — Not used. Normally a 0.4mV (8mA x 50mΩ) weight. 4 — Not used. Normally a 0.8mV (16mA x 50mΩ) weight. 5 — Not used. Normally a 1.6mV (32mA x 50mΩ) weight. 6 Charge Current, DACI 0 0 = Adds 0mV of charge current-sense voltage. 1 = Adds 3.2mV (64mA x 50mΩ) charge current-sense voltage. 6.4mV (min) (128mA x 50mA) sense voltage. 7 Charge Current, DACI 1 0 = Adds 0mV of charge current-sense voltage. 1 = Adds 6.4mV (128mA x 50mΩ) charge current-sense voltage. 8 Charge Current, DACI 2 0 = Adds 0mV of charge current-sense voltage. 1 = Adds 12.8mV (256mA x 50mΩ) charge current-sense voltage. 9 Charge Current, DACI 3 0 = Adds 0mV of charge current-sense voltage. 1 = Adds 25.6mV (512mA x 50mΩ) charge current-sense voltage. 10 Charge Current, DACI 4 0 = Adds 0mV of charge current-sense voltage. 1 = Adds 51.2mV (1024mA x 50mΩ) charge current-sense voltage. 11 Charge Current, DACI 5 0 = Adds 0mV of charge current-sense voltage. 1 = Adds 102.4mV (2048mA x 50mΩ) charge current-sense voltage. 150.4mV (max) (3008mA x 50mA) sense voltage. 12–15 — FUNCTION 0 = Adds 0mV of charge current-sense voltage. 1 = Sets charge current-sense voltage into overrange. 150.4mV (max) (3008mA x 50mA) sense voltage. *Command: 0x14 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 MAX1645B 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 50mΩ 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 MAX1645B is powered on, the BATT current regulates to 128mA. Any time 20 150.4 AVERAGE (CSIP - CSIN) VOLTAGE IN CURRENT REGULATION (mV) MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting 102.4 51.2 6.4 0x0080 0x0400 0x0800 0x0BC0 Figure 6. Average Voltage Between CSIP and CSIN vs. ChargingCurrent() Code ______________________________________________________________________________________ 0XFFFF Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting PIN BIT NAME 0 — Not used. Normally a 1mV weight. 1 — Not used. Normally a 2mV weight. 2 — Not used. Normally a 4mV weight. 3 — Not used. Normally an 8mV weight. 4 Charge Voltage, DACV 0 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 16mV of charger-voltage compliance, 1.024V (min). 5 Charge Voltage, DACV 1 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 32mV of charger-voltage compliance, 1.024V (min). 6 Charge Voltage, DACV 2 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 64mV of charger-voltage compliance, 1.024V (min). 7 Charge Voltage, DACV 3 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 128mV of charger-voltage compliance, 1.024V (min). 8 Charge Voltage, DACV 4 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 256mV of charger-voltage compliance, 1.024V (min). 9 Charge Voltage, DACV 5 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 512mV of charger-voltage compliance, 1.024V (min). 10 Charge Voltage, DACV 6 0 = Adds 0mA of charger-voltage compliance. 1 = Adds 1024mV of charger-voltage compliance. 11 Charge Voltage, DACV 7 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 2048mV of charger-voltage compliance. 12 Charge Voltage, DACV 8 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 4096mV of charger-voltage compliance. 13 Charge Voltage, DACV 9 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 8192mV of charger-voltage compliance. 14 Charge Voltage, DACV 10 0 = Adds 0mV of charger-voltage compliance. 1 = Adds 16384mV of charger-voltage compliance, 18432mV (max). 15 Charge Voltage, Overrange MAX1645B Table 5. ChargingVoltage()* FUNCTION 0 = Adds 0mV of charger-voltage compliance. 1 = Sets charger compliance into overrange, 18432mV. *Command: 0x15 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 MAX1645B 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 ______________________________________________________________________________________ 21 MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting 18.432V 16.800V VREF = 4.096V VDCIN > 20V VOLTAGE SET POINT (V0) 12.592V 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 (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 MAX1645B 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 22 AlarmWarning() is 0x16 (0b00010110). AlarmWarning() sets the ALARM_INHIBITED status bit in the MAX1645B if D15, D14, D13, D12, or D11 of the write-word protocol data equals 1. Table 6 summarizes the Alarm-Warning() 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 MAX1645B switching regulators remain off. ______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645B Table 6. AlarmWarning()* BIT BIT NAME 0 Error Code Not used FUNCTION 1 Error Code Not used 2 Error Code Not used 3 Error Code Not used 4 FULLY_DISCHARGED Not used 5 FULLY_CHARGED Not used 6 DISCHARGING Not used 7 INITIALIZING Not used 8 REMAINING_TIME_ ALARM Not used 9 REMAINING_CAPACITY_ ALARM Not used 10 Reserved Not used 11 TERMINATE_ DISCHARGE_ALARM 0 = Charge normally 1 = Terminate charging 12 OVER_TEMP_ALARM 0 = Charge normally 1 = Terminate charging 13 OTHER_ALARM 0 = Charge normally 1 = Terminate charging 14 TERMINATE_CHARGE_ ALARM 0 = Charge normally 1 = Terminate charging 15 OVER_CHARGE_ALARM 0 = Charge normally 1 = Terminate charging *Command: 0x16 ______________________________________________________________________________________ 23 MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting Interrupts and Alert Response Address The MAX1645B 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 pulls 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 MAX1645B, 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 try to respond by transmitting their address, and the device with the highest priority, or most leading zeros, are recognized and cleared. The process repeats until all devices requesting interrupts are addressed and cleared. The MAX1645B responds to the AlertResponse() address with 0x13, which is its address and a trailing 1. Charger Timeout The MAX1645B includes a timer that terminates charge if the charger has not received a ChargingVoltage() or ChargingCurrent() command in 175s. 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 terminates and both ChargingVoltage() and ChargingCurrent() commands are required to restart charging. A power-on reset also restarts charging at 128mA. DC-to-DC Converter The MAX1645B employs a buck regulator with a bootstrapped NMOS high-side switch and a low-side NMOS synchronous rectifier. DC-to-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. 24 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 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 / 2πRC = 1 / (2 ✕ π ✕ 33Ω ✕ 0.1µF) = 48kHz 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. Thermistor Bits Figure 9 shows the expected electrical behavior of a 103ETB-type thermistor (nominally 10kΩ at +25°C ±5% or better) to be used with the MAX1645B: • THERMISTOR_OR bit is set when the thermistor value is >100kΩ. 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 >30kΩ. The thermistor indicates a cold battery. This bit does not affect the charge. • THERMISTOR_HOT bit is set when the thermistor value is <3kΩ. This is a latched bit and is cleared by removing the battery or sending a POR with the ChargerMode() command. The MAX1645B charger is stopped unless the HOT_STOP bit is cleared in the ChargerMode() command or the RES_UR bit is set. See Table 7. • THERMISTOR_UR bit is set when the thermistor value is <500Ω (i.e., THM is grounded). Multiple bits can be set depending on the value of the thermistor (e.g., a thermistor that is 450Ω causes both the THERMISTOR_HOT and the THERMISTOR_UR bits to be set). The thermistor can be replaced by fixedvalue 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. ______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting MAX1645B 10ms S RESET CSSP BST IMAX R 3.0V R1 CSS MAX1645B Q ADAPTER IN LDO CSSN BST R Q DHI CCMP DHI CBST LX CHG S IMIN Q 0.25V DLO L1 DLO 1µs CSIP ZCMP 0.1V CSI R2 CSIN GMS LVC BATT COUT BATTERY GMI RFC 70kΩ GMV RFI 20kΩ DACV DACI CLS CONTROL ON CCS CCI * CCV * *OPTIONAL Figure 8. DC-to-DC Converter Functional Diagram ______________________________________________________________________________________ 25 Load and Source Switch Drivers The MAX1645B 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. • Load switch P2 is controlled by PDL. This P-channel MOSFET is turned off when the CVS rises to 100mV below BATT and turns on when CVS falls to 300mV below BATT. 1000 RESISTANCE (kΩ) MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting 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 Dropout Operation The MAX1645B has a 99.99% duty-cycle capability with a 10ms maximum on-time and 1µs 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). 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 can 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 can be used to “condition” battery 1, allowing it to be fully discharged prior to recharge. Table 7. Thermistor Bit Settings THERMISTOR STATUS BIT DESCRIPTION RES_UR and RES_HOT Underrange RES_HOT Hot (None) Normal RES_COLD Cold RES_OR and RES_COLD Overrange CONTROLLED CHARGE WAKE-UP CHARGE Allowed for timeout period Allowed Not allowed Not allowed Allowed for timeout period Allowed Allowed for timeout period Allowed Float charge* Not allowed *See Battery Present in the Operating Conditions section for more information. 26 ______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting SYSTEM POWER SUPPLY MAX1645B VCC +12V, -12V SYSTEM POWER CONTROL DC (UNREGULATED) / VBATTERY AC VBATTERY SMART BATTERY SYSTEM HOST (SMBus HOST) CRITICAL EVENTS BATTERY DATA/STATUS REQUESTS DC (UNREGULATED) SAFETY SIGNAL AC-DC CONVERTER (UNREGULATED) MAX1645B SMART BATTERY CHARGER CHARGING VOLTAGE/CURRENT REQUESTS SMBus CRITICAL EVENTS Figure 10. Typical Single Smart Battery System 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 8). Level 3 smart battery chargers are supersets of Level 2 chargers and, as such, support all Level 2 charger commands. 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 chemistry independent and, since it is defined as an SMBus slave device only, the smart battery charger is relatively inexpensive and easy to implement. Level 2 Smart Battery Charger Selecting External Components 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. Table 9 lists the suppliers’ contacts; Table 10 lists the recommended components and refers to the circuit of Figure 1. 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 or higher. This diode may not be necessary if P1 is used. The P-channel MOSFET P1 turns on when V CVS > VBATT. This eliminates the voltage drop and power con- ______________________________________________________________________________________ 27 AC SYSTEM POWER SUPPLY DC (UNREGULATED) / VBATTERY NOTE: SB 1 POWERING SYSTEM SB 2 CHARGING AC-DC CONVERTER (UNREGULATED) SMBus SMART BATTERY 2 SIGNAL SMBus SIGNAL SAFETY VBATT SMART BATTERY 1 SAFETY VCC +12V, -12V VBATT MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting SMBus SYSTEM HOST (SMBus HOST) SAFETY SIGNAL SMART BATTERY SELECTOR VCHARGE MAX1645B SMART BATTERY CHARGER CRITICAL EVENTS BATTERY DATA/STATUS REQUESTS SMBus Figure 11. Typical System Using Multiple Smart Batteries Table 8. Smart Battery Charger Type by SMBus Mode and Charge Algorithm Source CHARGE ALGORITHM SOURCE SMBus MODE BATTERY MODIFIED FROM BATTERY Slave only Level 2 Level 3 Slave/master Level 3 Level 3 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. 28 sumption of the Schottky diode. To minimize power loss, select a MOSFET with an RDS(ON) of 50mΩ 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. 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 50mΩ 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-to-DC converter maximum switching frequency of 400kHz). The low-side switch N2 should also have a current rating of at least 3A, have an RDS(ON) of 100mΩ 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. ______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting 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 50mΩ or less to minimize power loss and voltage drop. 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 one-half 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 = 21Vµs / L Higher inductor values decrease the ripple current. Smaller inductor values require higher saturation current capabilities and degrade efficiency. Typically, a 22µH inductor is ideal for all operating conditions. Table 9. Component Suppliers COMPONENT Inductor MOSFET Sense resistor Capacitor Diode MANUFACTURER PART Sumida CDRH127 series Coilcraft D03316P series Coiltronics UP2 series Internal Rectifier IRF7309 Fairchild FDS series Vishay-Siliconix Si4435/6 Dale WSL series IRC LR2010-01 series AVX TPS series, TAJ series Sprague 595D series Motorola 1N5817–1N5822 Nihon NSQ03A04 Central Semiconductor CMSH series Other Components CCV, CCI, and CCS are the compensation points for the three regulation loops. Bypass CCV with a 10kΩ resistor in series with a 0.01µF capacitor to GND. Bypass CCI and CCS with 0.01µF capacitors to GND. R7 and R13 serve as protection resistors to THM and CVS, respectively. To achieve acceptable accuracy, R6 should be 10kΩ 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 Figure 1. Use 1µF ceramic capacitors from CSSP and CSSN to GND. Smaller 0.1µF 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 MAX1645B. Layout and Bypassing Bypass DCIN with a 1µF 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. A ground plane is essential for optimum performance. In most applications, the circuit is 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. ______________________________________________________________________________________ 29 MAX1645B D3 is a signal-level diode, such as the 1N4148. This diode provides the supply current to the high-side MOSFET driver. MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting Table 10. Component Selection DESIGNATION DESCRIPTION C1, C2 input capacitors 22µF, 35V low-ESR tantalum capacitors AVX TPSE226M035R0300 C3, C4 output capacitors 22µF, 25V low-ESR tantalum capacitors AVX TPSD226M025R0200 C5, C19, C20 1µF, >30V ceramic capacitors C6, C7, C12 1µF ceramic capacitors C8, C14, C16 0.1µF ceramic capacitors C9 compensation capacitor 0.01µF ceramic capacitor C10, C11 compensation capacitors 1nF ceramic capacitors C13 1500pF ceramic capacitor C18, C24 0.1µF, >20V ceramic capacitors C23 0.1µF, >30V ceramic capacitor D1, D2 40V, 2A Schottky diodes Central Semiconductor CMSH2-40 D3, D4 Small-signal diodes Central Semiconductor CMPSH-3 L1 22µH, 3.6A buck inductor Sumida CDRH127-220 N1 high-side MOSFET 30V, 11.5A, high-side N-channel MOSFET (8-pin SO) Fairchild FDS6680 30V, 8.4A, low-side N-channel MOSFET N2 low-side MOSFET Fairchild FDS6612A or 30V, signal-level N-channel MOSFET 2N7002 P1, P2 30V, 11A P-channel MOSFETs load and source switches Fairchild FDS6675 R1 40mΩ ±1%, 0.5W battery current-sense resistor Dale WSL-2010/40mΩ/±1% R2 50mΩ ±1%, 0.5W source current-sense resistor Dale WSL-2010/50mΩ/±1% R3, R4 R3 + R4 >100kΩ input current-limit setting resistors R5, R7–R10, R17, R18 10kΩ ±5% resistors R6 10kΩ ±1% temperature sensor network resistor R11, R16 1Ω ±5% resistors R12 33Ω ±5% resistor R13 1kΩ ±5% resistor R14, R15 4.7Ω ±5% resistors Note: See Figure 1 for circuit configuration. 30 ______________________________________________________________________________________ Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting 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. Chip Information TRANSISTOR COUNT: 6996 ______________________________________________________________________________________ 31 MAX1645B • 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. 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. MAX1645B Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting Typical Operating Circuit ADAPTER IN PDS CVS DCIN CSSP MAX1645B REF CSSN LDO LOAD CLS GND BST DLOV DAC CCV DHI CCI LX 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 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.