MAX1535CETJ+T ,Highly Integrated Level 2 SMBus Battery ChargersFeaturesThe MAX1535B/MAX1535C/MAX1535D are highly inte-♦ Compliant with Level 2 Smart-Battery-Charg ..
MAX1536ETI ,3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-Down Regulator with Dynamic Output Voltage ControlApplicationso oMAX1536ETI -40 C to +85 C 28 Thin QFN 5mm x 5mmChipset/Graphics Cores Notebook Compu ..
MAX1536ETI+T ,3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-Down Regulator with Dynamic Output Voltage ControlApplicationso oMAX1536ETI -40 C to +85 C 28 Thin QFN 5mm x 5mmChipset/Graphics Cores Notebook Compu ..
MAX1538ETI ,4.75 to 28 V,power-source selector for dual-battery systemFeaturesThe MAX1538 selector provides power-source control ♦ Automatically Detects and Responds tof ..
MAX1538ETI+ ,Power-Source Selector for Dual-Battery SystemsELECTRICAL CHARACTERISTICS(V = V = V = 16.8V, C = 1µF, V = V = 0.93V, V = V = 28V, V = V = V = 0,BA ..
MAX1538ETI+T ,Power-Source Selector for Dual-Battery SystemsFeaturesThe MAX1538 selector provides power-source control ♦ Automatically Detects and Responds tof ..
MAX4173FESA ,Low-Cost / SOT23 / Voltage-Output / High-Side Current-Sense AmplifierELECTRICAL CHARACTERISTICS(V = 0 to +28V, V = +3V to +28V, V = 0, T = T to T , R = ¥ unless otherwi ..
MAX4173FEUT ,Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense AmplifierELECTRICAL CHARACTERISTICS(V = 0 to +28V, V = +3V to +28V, V = 0V, T = T to T , R = ∞ unless otherw ..
MAX4173FEUT+ ,Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense AmplifierFeaturesThe MAX4173 low-cost, precision, high-side current-♦ Low-Cost, Compact Current-Sense Soluti ..
MAX4173FEUT+T ,Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense AmplifierELECTRICAL CHARACTERISTICS(V = 0 to +28V, V = +3V to +28V, V = 0V, T = T to T , R = ∞ unless otherw ..
MAX4173FEUT-T ,Low-Cost / SOT23 / Voltage-Output / High-Side Current-Sense AmplifierMAX4173T/F/H19-1434; Rev 1; 5/99Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier
MAX4173HESA ,Low-Cost / SOT23 / Voltage-Output / High-Side Current-Sense AmplifierFeaturesThe MAX4173 low-cost, precision, high-side current-' Low-Cost, Compact Current-Sense Soluti ..
MAX1535BETJ+-MAX1535CETJ+-MAX1535CETJ+T
Highly Integrated Level 2 SMBus Battery Chargers
General DescriptionThe MAX1535B/MAX1535C/MAX1535D are highly inte-
grated, multichemistry battery chargers that simplify con-
struction of advanced smart chargers with a minimum
number of external components. They use Intel’s system
management bus (SMBus™) to control the charge volt-
age, charge current, and the maximum current drawn
from the AC adapter. High efficiency is achieved through
use of a constant off-time step-down topology with syn-
chronous rectification.
In addition to support of the Smart-Battery-Charger
Specifications Rev 1.1, the MAX1535B/MAX1535C/
MAX1535D include additional features. The maximum
current drawn from the AC adapter is programmable to
avoid overloads when supplying the load and the battery
charger simultaneously. This enables the user to reduce
the cost of the AC adapter. The MAX1535B/MAX1535C/
MAX1535D provide a digital output that indicates the
presence of an AC adapter. Based on the presence or
absence of the AC adapter, the MAX1535B/MAX1535C/
MAX1535D automatically select the appropriate source
for supplying power to the system by controlling two
external p-channel MOSFETs. Under system control, the
MAX1535B/MAX1535C/MAX1535D allow the battery to
undergo a relearning or conditioning cycle in which the
battery is completely discharged through the system
load and then recharged.
The MAX1535B/MAX1535C/MAX1535D are capable of
charging 2, 3, or 4 lithium-ion (Li+) cells in series, provid-
ing charge currents as high as 8A. The DC-DC converter
in the MAX1535B/MAX1535C/MAX1535D uses a high-
side p-channel switch with an n-channel synchronous
rectifier. The charge current and input current-limit sense
amplifiers have low input-offset errors and can use small-
value sense resistors (0.01Ω, typ).
The MAX1535B/MAX1535C/MAX1535D are available in
a 5mm x 5mm, 32-pin, thin QFN package and operate
over the extended -40°C to +85°C temperature range.
An evaluation kit is available to reduce design time.
ApplicationsNotebook and Subnotebook Computers
Tablet PCs
Portable Equipment with Rechargeable Batteries
FeaturesCompliant with Level 2 Smart-Battery-Charger
Specifications Rev 1.1 Intel SMBus 2-Wire Serial Interface±0.5% Charge-Voltage Accuracy11-Bit Charge-Voltage Resolution±3% Input Current-Limit AccuracyUse Small (10mΩ) Current-Sense Resistors8A Maximum Charge Current6-Bit Input and Charge-Current Resolution8V to 28V Input Voltage Range175s Charge Safety TimerAutomatic Selection of System Power SourceCharge Any Battery Chemistry (Li+, NiCd, NiMH,
Lead Acid, etc.)
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery ChargersI.C.
GND
CSIN
CSIP
PGND
DLO
DLOV
TOP VIEWVMAXIMAXDACVDDTHMSDASCL
DCIN
LDO
ACIN
REF
GND
CCS
CCI
CCVDHIVDHISRCCSSNCSSPPDLPDSACOK
INT
MAX1535B
MAX1535C
MAX1535D
THIN QFN (5mm x 5mm)
Pin Configuration
Ordering Information19-3261; Rev 2; 10/05
EVALUATION KIT
AVAILABLE
PARTTEMP RANGEPIN-
PACKAGE
PKG
CODEMAX1535BETJ-40°C to +85°C32 Thin QFN
(5mm x 5mm)T3255-4
SMBus is a trademark of Intel Corp.
Ordering Information continued at end of data sheet.
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
ABSOLUTE MAXIMUM RATINGSStresses 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.
DCIN, CSSP, CSSN, SRC, ACOKto GND .............-0.3V to +30V
DHIV to SRC.............................................................-6V to +0.3V
DHI, PDL, PDS to GND...............................-0.3V to VSRC + 0.3V
BATT, CSIP, CSIN to GND.....................................-0.3V to +20V
CSIP to CSIN, or CSSP to CSSN...........................-0.3V to +0.3V
CCI, CCS, CCV, DAC, REF to GND............-0.3V to VLDO + 0.3V
VDD, ACIN, SCL, SDA, DLOV, LDO, THM, INT, IMAX,
VMAX to GND...........................................................-0.3V to +6V
DLOV to LDO.........................................................-0.3V to +0.3V
DLO to PGND............................................-0.3V to VDLOV + 0.3V
PGND to GND.......................................................-0.3V to +0.3V
LDO Short-Circuit Current...................................................50mA
Continuous Power Dissipation (TA= +70°C)
32-Pin Thin QFN (derate 21.3mW/°C above +70°C)...1702mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1. VDCIN= VCSSP= VCSSN= 18V, VBATT= VCSIP= VCSIN= 12V, VDD= 3.3V, ACIN = PGND = GND, LDO = DLOV,
VMAX = IMAX = REF, CLDO= 1µF, CDHIV= 0.1µF, CREF= 1µF, TA
= 0°C to +85°C. Typical values are at TA= +25°C, unless other-
wise noted.)
PARAMETERCONDITIONSMINTYPMAXUNITS
CHARGE-VOLTAGE REGULATIONChargeVoltage() = 0x41A0 and 0x3130-0.5+0.5
ChargeVoltage() = 0x20D0-0.8+0.8Charge-Voltage Accuracy
ChargeVoltage() = 0x1060-1.0+1.0
ChargeVoltage() = 0x41A016.71616.80016.884
ChargeVoltage() = 0x313012.52912.59212.655
ChargeVoltage() = 0x20D08.3328.4008.468Full-Charge Voltage
ChargeVoltage() = 0x10604.1504.1924.234
CHARGE-CURRENT REGULATIONCSIP-to-CSIN Full-Scale Current-
Sense Voltage VBATT = 12V 76.60 80.64 84.67 mVCompliance Current Accuracy 10mΩ sense resistor (R2 in Figure 1) between CSIP and
CSIN; ChargeCurrent() = 0x1F80 -5 +5 %10mΩ sense resistor (R2 in Figure 1) between CSIP and
CSIN; ChargeCurrent() = 0x1F80 7.660 8.064 8.467 ACharge Current 10mΩ sense resistor (R2 in Figure 1) between CSIP and
CSIN; ChargeCurrent() = 0x0080 128 mABATT/CSIP/CSIN Input Voltage
Range 0 19 VVDCIN = 0V, or charger not switching 0.1 1.0 CSIP/CSIN Input Current VCSIP = VCSIN = 12V 300 700 µA
INPUT-CURRENT REGULATIONCSSP-to-CSSN Full-Scale
Current-Sense Voltage VDCIN = 18V 104.5 110.0 115.5 mV
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
PARAMETERCONDITIONSMINTYPMAXUNITS10mΩ sense resistor (R1 in Figure 1) between CSSP and
CSSN; InputCurrent() = 0x1580 (11.008A) -5 +510mΩ sense resistor (R1 in Figure 1) between CSSP and
CSSN; InputCurrent() = 0x1000 (8.192A) -3 +310mΩ sense resistor (R1 in Figure 1) between CSSP and
CSSN; InputCurrent() = 0x0800 (4.096A) -6.5 +6.5% Input Current-Limit AccuracyPOR (InputCurrent() = 0x0080) 256 mACSSP/CSSN Input Voltage Range 8 28 VVDCIN = 0V 0.1 1.0 CSSP/CSSN Input Current VCSSP = VCSSN = VDCIN > 8.0V 300 750 µA
SUPPLY AND LINEAR REGULATORDCIN Input Voltage Range 8 28 VDCIN falling 7.0 7.4 DCIN Undervoltage-Lockout Trip
Point DCIN rising 7.50 7.85 VDCIN Quiescent Current 8V < VDCIN < 28V 2.7 6.0 mAVBATT = 19V, VDCIN = 0V, or charger not switching 0.1 1.0 BATT Input Current VBATT = 2V to 19V, VDCIN > VBATT + 0.3V 200 500 µALDO Output Voltage 8V < VDCIN < 28V, no load 5.25 5.40 5.50 VLDO Load Regulation 0 < ILDO < 10mA 34 100 mVLDO Undervoltage Lockout Trip
Point VDCIN = 8V 3.20 4.00 5.15 VVDD Range 2.7 5.5 VVDD UVLO Rising Threshold 2.5 2.7 VVDD UVLO Hysteresis 100 mVVDD Quiescent Current VDCIN < 6V, VDD = 5.5V, VSCL = VSDA = 5.5V 17 27 µA
REFERENCEREF Output Voltage 0 < IREF < 500µA 4.083 4.096 4.109 VREF Undervoltage-Lockout Trip
Point REF falling 3.1 3.9 V
TRIP POINTSBATT POWER_FAIL Threshold VDCIN - VBATT, DCIN falling 50 100 150 mVBATT POWER_FAIL Threshold
Hysteresis 100 200 300 mVACIN Threshold ACIN rising 1.966 2.048 2.130 VACIN Threshold Hysteresis 10 20 30 mVACIN Input Bias Current VACIN = 2.048V -1 +1 µA
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1. VDCIN= VCSSP= VCSSN= 18V, VBATT= VCSIP= VCSIN= 12V, VDD= 3.3V, ACIN = PGND = GND, LDO = DLOV,
VMAX = IMAX = REF, CLDO= 1µF, CDHIV= 0.1µF, CREF= 1µF, TA
= 0°C to +85°C. Typical values are at TA= +25°C, unless other-
wise noted.)
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
PARAMETERCONDITIONSMINTYPMAXUNITSSWITCHING REGULATORVBATT = 16.0, VDCIN = 21.0 540 600 660 Off-Time VBATT = 19.0, VDCIN = 21.0 230 270 310 nsDLOV Supply Current ChargerMode() = 0x0001 5 10 µAMaximum Discontinuous Mode
Peak Current 0.5 ABattery Undervoltage Charge
Current VBATT = 2.6V 128 mADHIV Output Voltage With respect to SRC -4.5 -5.0 -5.5 VDHIV Sink Current 10 mADHI On-Resistance Low VDHI = VDHIV, IDHI = -10mA 4 7 ΩDHI On-Resistance High VDHI = VSRC, IDHI = 10mA 1 3 ΩDLO On-Resistance High VDLOV = 4.5V, IDLO = 100mA 4 7 ΩDLO On-Resistance Low VDLOV = 4.5V, IDLO = -100mA 1 3 Ω
ERROR AMPLIFIERSGMV Transconductance ChargeVoltage () = 0x41A0, VBATT = 16.8V 0.0625 0.1250 0.2500 µA/mVGMI Transconductance ChargeCurrent () = 0x1F80, VCSIP - VCSIN = 80.64mV 0.5 1 2 µA/mVGMS Transconductance InputCurrent () = 0x1580, VCSSP - VCSSN = 110.08mV 0.5 1 2 µA/mVCCI Clamp Voltage 0.25V < VCCI < 2.0V 150 300 600 mVCCV Clamp Voltage 0.25V < VCCV < 2.0V 150 300 600 mVCCS Clamp Voltage 0.25V < VCCS < 2.0V 150 300 600 mV
ACOKACOK Input Voltage Range 0 28 VACOK Sink Current V ACOK = 0.4V, ACIN = 1.5V 1 mAACOK Leakage Current V ACOK = 28V, ACIN = 2.5V 1 µA
PDS, PDL SWITCH CONTROLPDS Switch Turn-Off Threshold DCIN with respect to BATT, DCIN falling 50 100 150 mVPDL Switch Turn-On Threshold DCIN with respect to BATT, DCIN falling 50 100 150 mVPDS Switch Threshold Hysteresis DCIN with respect to BATT 200 mVPDL Switch Threshold Hysteresis DCIN with respect to BATT 200 mVPDS Output Low Voltage, PDS
Below SRC IPDS = 0V 8 10 12 VPDS Turn-On Current PDS = SRC 6 12 mAPDS Turn-Off Current VPDS = VSRC - 2V, VDCIN = 16V 10 50 mAPDL Turn-On Resistance PDL = GND 50 100 150 kΩPDL Turn-Off Current VCSSN - VPDL = 1.5V 6 12 mAPDL and PDS Transition Delay
Time PDS and PDL are unloaded 4 10 15 µs
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1. VDCIN= VCSSP= VCSSN= 18V, VBATT= VCSIP= VCSIN= 12V, VDD= 3.3V, ACIN = PGND = GND, LDO = DLOV,
VMAX = IMAX = REF, CLDO= 1µF, CDHIV= 0.1µF, CREF= 1µF, TA
= 0°C to +85°C. Typical values are at TA= +25°C, unless other-
wise noted.)
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
PARAMETERCONDITIONSMINTYPMAXUNITSPDL-to-PDS Switchover Time in
Relearn Mode PDS and PDL are unloaded 4 10 16 µs
MAXIMUM CHARGE-VOLTAGE SETTING VBATT to VVMAX Ratio VMAX = 2V, ChargeVoltage () = 0x4B00 4.95 5.0 5.05 V/VVMAX Input Voltage Range 0 VREF VVMAX Input Bias Current 0 < VVMAX < VREF 1 µA
MAXIMUM CHARGE-CURRENT SETTINGICHARGE to VIMAX Ratio VIMAX = 0.8V, ChargeCurrent () = 0x1F80 4.75 5 5.25 A/VIMAX Input Voltage Range 0 VREF VIMAX Input Bias Current 0 < VIMAX < VREF 1 µA
THERMISTOR COMPARATORThermistor Overrange Threshold VDD = 2.7V to 5.5V, THM falling 89.5 91 92.5 % of V D D Thermistor Cold Threshold VDD = 2.7V to 5.5V, THM falling 73.5 75 76.5 % of V D D Thermistor Hot Threshold VDD = 2.7V to 5.5V, THM falling 21.5 23 24.5 % of V D D Thermistor Underrange
Threshold VDD = 2.7V to 5.5V, THM falling 3.5 5 6.5 % of VDDThermistor Comparator
Hysteresis All four comparators, VDD = 2.7V to 5.5V 50 mV
SMBus INTERFACE LEVEL SPECIFICATIONS (VDD = 2.7V to 5.5V)SDA/SCL Input Low Voltage VDD = 2.7V to 5.5V 0.8 VSDA/SCL Input High Voltage VDD = 2.7V to 5.5V 2.1 VSDA/SCL Input Bias Current VDD = 2.7V to 5.5V -1 +1 µASDA, INT Output Sink Current VSDA = 0.4V 6 mAINT Output High Leakage Current V INT = 5.5V 1 µAINT Output Low Voltage I INT = 1mA 25 200 mV
SMBus TIMING SPECIFICATIONS (VDD = 2.7V to 5.5V)SMBus Frequency 10 100 kHzSMBus Free Time 4.7 µsStart Condition Setup Time from
SCL 4.7 µsStart Condition Hold Time from
SCL 4 µsStop Condition Setup Time from
SCL 4 µsSDA Hold Time from SCL 300 nsSDA Setup Time from SCL 250 nsSCL Low Timeout (Note 1) 25 35 ms
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1. VDCIN= VCSSP= VCSSN= 18V, VBATT= VCSIP= VCSIN= 12V, VDD= 3.3V, ACIN = PGND = GND, LDO = DLOV,
VMAX = IMAX = REF, CLDO= 1µF, CDHIV= 0.1µF, CREF= 1µF, TA
= 0°C to +85°C. Typical values are at TA= +25°C, unless other-
wise noted.)
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
PARAMETERCONDITIONSMINTYPMAXUNITSSCL Low Period 4.7 µsSCL High Period 4 µsMaximum Charging Period
Without a ChargeVoltage() or
ChargeCurrent() Command 140 175 210 s
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1. VDCIN= VCSSP= VCSSN= 18V, VBATT= VCSIP= VCSIN= 12V, VDD= 3.3V, ACIN = PGND = GND, LDO = DLOV,
VMAX = IMAX = REF, CLDO= 1µF, CDHIV= 0.1µF, CREF= 1µF, TA
= 0°C to +85°C. Typical values are at TA= +25°C, unless other-
wise noted.)
PARAMETERCONDITIONSMINTYPMAXUNITS
CHARGE-VOLTAGE REGULATIONChargeVoltage() = 0x41A0 and 0x3130-1.6+1.6
ChargeVoltage() = 0x20D0-1.6+1.6Charge-Voltage Accuracy
ChargeVoltage() = 0x1060-1.8+1.8
ChargeVoltage() = 0x41A016.53217.068
ChargeVoltage() = 0x313012.39012.794
ChargeVoltage() = 0x20D08.2668.534Full-Charge Voltage
ChargeVoltage() = 0x10604.1164.268
CHARGE-CURRENT REGULATIONCSIP-to-CSIN Full-Scale Current-
Sense Voltage VBATT = 12V 72.58 88.70 mVCompliance Current Accuracy 10mΩ sense resistor (R2 in Figure 1) between CSIP and
CSIN; ChargeCurrent() = 0x1F80 -10 +10 %Charge Current 10mΩ sense resistor (R2 in Figure 1) between CSIP and
CSIN; ChargeCurrent() = 0x1F80 7.258 8.870 ABATT/CSIP/CSIN Input Voltage
Range 0 19 VCSIP/CSIN Input Current VCSIP = VCSIN = 12V 800 µA
INPUT-CURRENT REGULATIONCSSP-to-CSSN Full-Scale
Current-Sense Voltage VDCIN = 18V 99 121 mV10mΩ sense resistor (R1 in Figure 1) between CSSP and
CSSN; InputCurrent() = 0x1580 (11.008A) -10 +1010mΩ sense resistor (R1 in Figure 1) betweenCSSP and CSSN; InputCurrent() = 0x1000(8.192A)-8 +8 Input Current-Limit Accuracy10mΩ sense resistor (R1 in Figure 1) between CSSP and
CSSN; InputCurrent() = 0x0800 (4.096A) -10 +10%
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1. VDCIN= VCSSP= VCSSN= 18V, VBATT= VCSIP= VCSIN= 12V, VDD= 3.3V, ACIN = PGND = GND, LDO = DLOV,
VMAX = IMAX = REF, CLDO= 1µF, CDHIV= 0.1µF, CREF= 1µF, TA
= -40°C to +85°C, unless otherwise noted.) (Note 2)
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
PARAMETERCONDITIONSMINTYPMAXUNITSCSSP/CSSN Input Voltage Range 8 28 VCSSP/CSSN Input Current VCSSP = VCSSN = VDCIN > 8.0V 800 µASUPPLY AND LINEAR REGULATORDCIN Input Voltage Range 8 28 VDCIN falling 7.0 DCIN Undervoltage-Lockout Trip
Point DCIN rising 7.85 VDCIN Quiescent Current 8V < VDCIN < 28V 8 mABATT Input Current VBATT = 2V to 19V, VDCIN > VBATT + 0.3V 800 µALDO Output Voltage 8V < VDCIN < 28V, no load 5.15 5.65 VLDO Load Regulation 0 < ILDO < 10mA 100 mVLDO Undervoltage-Lockout Trip
Point VDCIN = 8V 3.00 5.35 VVDD Range 2.7 5.5 VVDD Quiescent Current VDCIN < 6V, VDD = 5.5V, VSCL = VSDA = 5.5V 27 µAREFERENCEREF Output Voltage 0 < IREF < 500µA 4.035 4.157 VREF Undervoltage-Lockout Trip
Point REF falling 3.9 VTRIP POINTSBATT POWER_FAIL Threshold VDCIN - VBATT, DCIN falling 60 160 mVBATT POWER_FAIL Threshold
Hysteresis 90 310 mVACIN Threshold ACIN rising 1.966 2.129 VACIN Threshold Hysteresis 5 35 mVSWITCHING REGULATORVBATT = 16.0, VDCIN = 21.0 540 660 Off-Time VBATT = 19.0, VDCIN = 21.0 230 310 nsDLOV Supply Current ChargerMode() = 0x0001 10 µABattery Undervoltage Charge
Current VBATT = 2.6V 64 192 mADHIV Output Voltage With respect to SRC -4.4 -5.5 VDHIV Sink Current 10 mADHI On-Resistance Low VDHI = VDHIV, IDHI = -10mA 7 ΩDHI On-Resistance High VDHI = VSRC, IDHI = 10mA 3 ΩDLO On-Resistance High VDLOV = 4.5V, IDLO = 100mA 7 ΩDLO On-Resistance Low VDLOV = 4.5V, IDLO = -100mA 3 ΩERROR AMPLIFIERSGMV Transconductance ChargeVoltage() = 0x41A0, VBATT = 16.8V 0.0625 0.2500 µA/mV
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1. VDCIN= VCSSP= VCSSN= 18V, VBATT= VCSIP= VCSIN= 12V, VDD= 3.3V, ACIN = PGND = GND, LDO = DLOV,
VMAX = IMAX = REF, CLDO= 1µF, CDHIV= 0.1µF, CREF= 1µF, TA
= -40°C to +85°C, unless otherwise noted.) (Note 2)
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
PARAMETERCONDITIONSMINTYPMAXUNITSGMI Transconductance ChargeCurrent() = 0x1F80, VCSIP - VCSIN = 80.64mV 0.5 2.0 µA/mVGMS Transconductance InputCurrent() = 0x1580, VCSSP - VCSSN = 110.08mV 0.5 2.0 µA/mVCCI Clamp Voltage 0.25V < VCCI < 2.0V 140 600 mVCCV Clamp Voltage 0.25V < VCCV < 2.0V 140 600 mVCCS Clamp Voltage 0.25V < VCCS < 2.0V 140 600 mVACOKACOK Input Voltage Range 0 28 VACOK Sink Current V ACOK = 0.4V, ACIN = 1.5V 1 mAPDS, PDL SWITCH CONTROLPDS Switch Turn-Off Threshold DCIN with respect to BATT, DCIN falling 40 160 mVPDL Switch Turn-On Threshold DCIN with respect to BATT, DCIN falling 40 160 mVPDS Output Low Voltage, PDS
Below SRC IPDS = 0 8 12 VPDS Turn-On Current PDS = SRC 6 mAPDS Turn-Off Current VPDS = VSRC - 2V, VDCIN = 16V 10 mAPDL Turn-On Resistance PDL = GND 40 160 kΩPDL Turn-Off Current VCSSN - VPDL = 1.5V 6 mAPDL and PDS Transition Delay
Time PDS and PDL are unloaded 4 15 µsPDL-to-PDS Switchover Time in
Relearn Mode PDS and PDL are unloaded 4 16 µsMAXIMUM CHARGE-VOLTAGE SETTINGVMAX Input Voltage Range 0 VREF VVMAX to VBATT Ratio VVMAX = 2V, ChargeVoltage() = 0x4B00 4.9 5.1 V/VMAXIMUM CHARGE-CURRENT SETTINGIMAX Input Voltage Range 0 VREF VIMAX to ICHARGE Ratio VIMAX = 0.8V, ChargeCurrent() = 0x1F80 4.5 5.5 A/VTHERMISTOR COMPARATORThermistor Overrange Threshold VDD = 2.7V to 5.5V, THM falling 89.5 92.5 % of VDDThermistor Cold Threshold VDD = 2.7V to 5.5V, THM falling 73.5 76.5 % of VDDThermistor Hot Threshold VDD = 2.7V to 5.5V, THM falling 21.5 24.5 % of VDDThermistor Underrange Threshold VDD = 2.7V to 5.5V, THM falling 3.5 6.5 % of VDDSMBus INTERFACE LEVEL SPECIFICATIONS (VDD = 2.7V TO 5.5V)SDA/SCL Input Low Voltage VDD = 2.7V to 5.5V 0.8 VSDA/SCL Input High Voltage VDD = 2.7V to 5.5V 2.15 VSDA, INT Output Sink Current VSDA = 0.4V 6 mAINT Output Low Voltage I INT = 1mA 200 mV
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1. VDCIN= VCSSP= VCSSN= 18V, VBATT= VCSIP= VCSIN= 12V, VDD= 3.3V, ACIN = PGND = GND, LDO = DLOV,
VMAX = IMAX = REF, CLDO= 1µF, CDHIV= 0.1µF, CREF= 1µF, TA
= -40°C to +85°C, unless otherwise noted.) (Note 2)
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
PARAMETERCONDITIONSMINTYPMAXUNITSSMBus TIMING SPECIFICATIONS (VDD = 2.7V TO 5.5V)SMBus Frequency 10 100 kHzSMBus Free Time 4.7 µsStart Condition Setup Time from
SCL 4.7 µsStart Condition Hold Time from
SCL 4 µsStop Condition Setup Time from
SCL 4 µsSDA Hold Time from SCL 300 nsSDA Setup Time from SCL 250 nsSCL Low Timeout (Note 1) 25 35 msSCL Low Period 4.7 µsSCL High Period 4 µsMaximum Charging Period
Without a ChargeVoltage() or
ChargeCurrent() Command 130 220 s
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1. VDCIN= VCSSP= VCSSN= 18V, VBATT= VCSIP= VCSIN= 12V, VDD= 3.3V, ACIN = PGND = GND, LDO = DLOV,
VMAX = IMAX = REF, CLDO= 1µF, CDHIV= 0.1µF, CREF= 1µF, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
Note 1:Devices participating in a transfer time out when any clock low exceeds the 25ms minimum timeout period. Devices that
have detected a timeout condition must reset the communication no later than the 35ms maximum timeout period. Both a
master and a slave must adhere to the maximum value specified as it incorporates the cumulative stretch limit for both a
master (10ms) and a slave (25ms).
Note 2:Specifications to -40°C are guaranteed by design, not production tested.
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
Typical Operating Characteristics
(Circuit of Figure 1, VDCIN= 20V, TA= +25°C, unless otherwise noted.)
TRANSIENT RESPONSE
(BATTERY REMOVAL AND INSERTION)
MAX1535 toc01
4ms/div
A: BATTERY VOLTAGE, 500mV/div, AC-COUPLED
B: VCCV, 500mV/div
C: VCCI, 500mV/div
D: CHARGE CURRENT, 2A/div
16.8VDCCB
BATT INSERTED
BATT REMOVED
LOAD SWITCH CONTROL
(ADAPTER INSERTION)
MAX1535 toc02
200μs/div
A: ADAPTER INPUT VOLTAGE, 20V/div
B: VCSSN, 20V/div
C: VPDS, 20V/div
D: VPDL, 20V/div
SYSTEM LOAD TRANSIENT
MAX1535 toc03
400μs/div
A: VBATT, 500mV/div, AC-COUPLED
B: VCCS, 500mV/div
C: VCCI, 500mV/div
D: AC ADAPTER CURRENT, 5A/div
E: SYSTEM LOAD, 5A/div
F: CHARGE CURRENT, 5A/divBCB
LDO LOAD REGULATION
(VIN = 20V)
MAX1535 toc04
LDO CURRENT (mA)
LDO VOLTAGE ERROR (%)642
LDO LINE REGULATIONMAX1535 toc05
INPUT VOLTAGE (V)
LDO VOLTAGE ERROR (%)201612
REF LOAD REGULATION
MAX1535 toc06
REF LOAD CURRENT (μA)
REF VOLTAGE ERROR (%)
EFFICIENCY vs. CHARGE CURRENT
(CONSTANT-VOLTAGE MODE)
MAX1535 toc08
EFFICIENCY (%)42
VCHARGE = 8.4V
VCHARGE = 12.6V
VCHARGE = 16.8V
REF VOLTAGE ERROR vs. TEMPERATUREMAX1535 toc07
REF VOLTAGE ERROR (%)6040200-20
-40100
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
FREQUENCY vs. VIN - VBATTMAX1535 toc10
VIN - VBATT (V)
FREQUENCY (kHz)1284
CHARGE-VOLTAGE ACCURACY
MAX1535 toc11
CHARGEVOLTAGE() CODE (V)
CHARGE VOLTAGE ERROR (%)128
CHARGE-CURRENT ACCURACY
MAX1535 toc12
CHARGECURRENT() SETTING (A)
CHARGE-CURRENT ERROR (%)42
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VDCIN= 20V, TA= +25°C, unless otherwise noted.)
EFFICIENCY vs. CHARGE CURRENT
(CONSTANT-CURRENT MODE)MAX1535 toc09
CHARGE CURRENT (A)
EFFICIENCY (%)42
VCHARGE = 8.4V
VCHARGE = 12.6V
VCHARGE = 16.8V
INPUT-CURRENT ACCURACYMAX1535 toc13
INPUTCURRENT() SETTING (A)
INPUT CURRENT ERROR (%)8642
INPUT/CHARGE CURRENT
vs. SYSTEM LOAD CURRENT
MAX1535 toc14
SYSTEM LOAD CURRENT (A)
INPUT/CHARGE CURRENT (A)42
CHARGECURRENT() = 4A
INPUTCURRENT() = 6A
INPUT CURRENT
CHARGE CURRENT
MAXIMUM CHARGE VOLTAGE vs. IMAXMAX1535 toc15
MAXIMUM CHARGE VOLTAGE (V)321
SLOPE ≈ 5V/V
MAXIMUM CHARGE CURRENT vs. VMAXMAX1535 toc16
MAXIMUM CHARGE CURRENT (A)321
SLOPE ≈ 5A/V
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
Pin Description
PINNAMEFUNCTIONDCINDC Supply Voltage Input. Bypass DCIN to power ground (PGND) with a 1µF ceramic capacitor.
2LDO5.4V Li near - Reg ul ator Outp ut. The l i near r eg ul ator p ow er s the i nter nal ci r cui tr y of the d evi ce. The i np ut of the l i near eg ul ator i s sup p l i ed fr om D C IN . Byp ass LD O w i th a 1µF cer am i c cap aci tor to GN D .ACINAC Adapter Detect Input. This uncommitted comparator input can be used to detect if the AC adapter voltage is
available for charging.REF4.096V (Typical) Reference Voltage Output. Bypass REF with a 1µF ceramic capacitor to GND.GNDAnalog GroundCCSInput Current-Limit Regulation Loop Compensation Point. Connect a 0.01µF capacitor to GND.CCICharge-Current Regulation Loop Compensation Point. Connect a 0.01µF capacitor to GND.CCVCharge-Voltage Regulation Loop Compensation Point. Connect a 20kΩ resistor in series with a 0.01µF capacitor
to GND.VMAXAnalog Control Input for Setting the Maximum Charge Voltage. The maximum charge voltage can never go above
the limit set by VMAX. The ratio of maximum charge voltage to VMAX voltage is 5V/V.IMAXAnalog Control Input for Setting the Maximum Charge Current. The maximum charge current can never go above
the limit set by IMAX. The ratio of maximum charge current to IMAX voltage is 5A/V.DACDAC Voltage Output. Bypass DAC with a 0.1µF ceramic capacitor to GND.VDDLogic Circuitry Supply Voltage Input. The voltage range of VDD is 2.7V to 5.5V.THMThermistor Voltage InputSDASMBus Data Input/Output. SDA is an open-drain output. An external pullup resistor is needed.SCLSMBus Clock Input. An external pullup resistor is needed.INTInterrupt Output. INT is an open-drain output. An external pullup resistor is needed.I.C.Internally Connected Pin. Leave it unconnected or connect it to ground.GNDAnalog GroundBATTBattery Voltage InputCSINNegative Input to the Charge Current-Sense AmplifierCSIPPositive Input to the Charge Current-Sense Amplifier. Connect a 10mΩ current-sense resistor from CSIP to CSIN.PGNDPower GroundDLOLow-Side Power MOSFET Gate Driver Output. Connect DLO to the gate of the low-side n-channel MOSFET.DLOVLow-Side Gate Driver Supply. Bypass DLOV with a 0.1µF ceramic capacitor to PGND.DHIVHigh-Side Gate Driver Supply. Bypass DHIV with a 0.1µF ceramic capacitor to SRC.DHIHigh-Side Power MOSFET Gate Driver Output. Connect DHI to the gate of the high-side p-channel MOSFET.SRCSource Connection for PDS and PDL Switch DriversCSSNNegative Input to the Input Current-Limit Sense AmplifierCSSPPositive Input to the Input Current-Limit Sense Amplifier. Connect a 10mΩ current-sense resistor from CSSN.PDLSystem Load P-Channel MOSFET Switch Driver Output. When the part is powered down, the PDL output is pulled
to ground through an internal 100kΩ resistor.PDSPower Source P-Channel MOSFET Switch Driver Output. When the part is powered down, the PDS output is pulled
to SRC through an internal 1MΩ resistor.ACOKAC Detect Output. This high-voltage open-drain output pulls low when ACIN is less than REF/2.
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
Detailed DescriptionThe MAX1535B/MAX1535C/MAX1535D include all the
functions necessary to charge Li+, NiMH, and NiCd
smart batteries. A high-efficiency, synchronous-recti-
fied, step-down DC-DC converter is used to implement
a precision constant-current, constant-voltage charger
with input current limiting. The DC-DC converter uses
an external p-channel MOSFET as the buck switch and
an external n-channel MOSFET as the synchronous
rectifier to convert the input voltage to the required
charge current and voltage. The charge current and
input current-limit sense amplifiers have low input-offset
errors and can use small-value sense resistors.
The MAX1535B/MAX1535C/MAX1535D feature a volt-
age-regulation loop (CCV) and two current-regulation
loops (CCI and CCS). The loops operate independently
of each other. The CCV voltage-regulation loop moni-
tors BATT to ensure that its voltage never exceeds the
voltage set by the ChargeVoltage() command. The CCI
battery current-regulation loop monitors current deliv-
ered to BATT to ensure that it never exceeds the cur-
rent limit set by the ChargeCurrent() command. The
charge current-regulation loop is in control as long as
the BATT voltage is below the set point. When the BATT
voltage reaches its set point, the voltage-regulation
loop takes control and maintains the battery voltage at
the set point. A third loop (CCS) takes control and
reduces the charge current when the sum of the sys-
tem load and the input current to the charger exceeds
the power-source current limit set by the InputCurrent()
command. The MAX1535B/MAX1535C/MAX1535D also
allow the user to clamp the programmed charge cur-
rent and charge voltage. This feature effectively avoids
damage to the battery if the charger was programmed
with invalid data.
Based on the presence or absence of the AC adapter,
the MAX1535B/MAX1535C/MAX1535D automatically
select the appropriate source for supplying power to the
system. A p-channel load switch controlled from the
PDL output and a similar p-channel source switch con-
trolled from the PDS output are used to implement this
function. The MAX1535B/MAX1535C/MAX1535D can be
programmed by a microcontroller (µC) to perform a
relearning, or conditioning, cycle in which the battery is
isolated from the charger and completely discharged
through the system load. When the battery reaches
100% depth of discharge, it is recharged to full capacity
(contact the battery-pack manufacturers for the 100%
depth of discharge threshold).
The circuit shown in Figure 1 demonstrates a typical
application for smart-battery systems.
Setting Charge VoltageThe SMBus specification allows for a 16-bit
ChargeVoltage() command that translates to a 1mV LSB
and a 65.535V full-scale voltage; therefore, the
ChargeVoltage() code corresponds to the output volt-
age in millivolts. The MAX1535B/MAX1535C/MAX1535D
ignore the first 4 LSBs, and uses the next 11 bits to con-
trol the voltage DAC. The charge voltage range of the
MAX1535B/MAX1535C/MAX1535D is 0 to 19.200V. All
codes requesting charge voltage greater than 19.200V
result in a voltage setting of 19.200V. All codes request-
ing charge voltage below 1.024V result in a voltage set
point of zero, which terminates charging.
The VMAX pin can be used to set an upper limit to the
charge voltage. This feature supercedes the value set
with the ChargeVoltage() command when charge volt-
age is greater than VCHARGE_MAX. The voltage range
of VMAX is from 0 to VREF. The maximum charge volt-
age can be related to the voltage on VMAX using the
following equation:
where VVMAXis the voltage on the VMAX pin.
Setting Charge CurrentThe SMBus specification allows for a 16-bit
ChargeCurrent() command that translates to a 1mA
LSB and a 65.535A full-scale current using a 10mΩ
current-sense resistor (R2 in Figure 1). Equivalently, the
ChargeCurrent() value sets the voltage across CSIP
and CSIN inputs in 10µV per LSB increment. The
MAX1535B/MAX1535C/MAX1535D ignore the first 7
LSBs and use the next 6 bits to control the current
DAC. The charge-current range of the MAX1535B/
MAX1535C/MAX1535D is 0 to 8.064A using a 10mΩ
current-sense resistor. All codes requesting charge
current above 8.064A result in a current setting of
8.064A. All codes requesting charge current between
1mA to 128mA result in a current setting of 128mA. The
default charge-current setting at power-on reset (POR)
is also 128mA.
The IMAX pin can be used to set an upper limit to the
charge current. This feature supercedes the value set
with the ChargeCurrent() command when charge cur-
rent is greater than ICHARGE_MAX. The voltage range of
IMAX is from 0 to VREF. The maximum charge current
can be related to the voltage on IMAX using the follow-
ing equation:AVCHARGEMAXIMAX_=×5VVCHARGEMAXVMAX_=×5
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery ChargersCSSPCSSN
LDO
LDO
DHI
DLOV
DLO
PGND
CSIP
CSIN
BATT
GND
DCIN
LDO
ACIN
CCS
ACOK
VDD
CCV
CCI
DAC
REF
INPUT
VDD
SCL
SDA
TEMP
GND
HOST
BATT+
SCL
SDA
TEMP
BATT-
SMART
BATTERY
AC ADAPTER INPUT
8.5V TO 24V
365kΩ
49.9kΩ
1μFR1
0.01Ω
20kΩ
4.3μH
GNDPGND
0.01Ω
1MΩ
GPIO
VCC
SRC
PDS
C11
0.1μF
1μF
1μF
R11
33Ω
VMAX
IMAX
C12
0.01μF
C13
0.01μF
C14
0.01μF
C10
0.1μF
22μF
22μF
P4 (OPTIONAL)
INT
10kΩ
10kΩ
10kΩ
R10
10kΩ
PDLP2
R12
14.7kΩ
R13
100kΩR14
137kΩ
R15
49.9kΩ
TO SYSTEM LOAD
1μF
SCL
SDA
THM
DHIV
22μF
22μF
1μF
MAX1535B
MAX1535C
MAX1535D
Figure 1. Standard Application Circuit
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargers
Setting Input-Current LimitThe total input current, from a wall cube or other DC
source, is the sum of the system supply current and the
current required by the charger. The MAX1535B/
MAX1535C/MAX1535D reduce the source current by
decreasing the maximum charge current when the input
current exceeds the set input current limit. This technique
does not truly limit the input current. As the system sup-
ply current rises, the available charge current drops pro-
portionally to zero. Thereafter, the total input current can
increase without limit.
An internal amplifier compares the differential voltage
between CSSP and CSSN to a scaled voltage set by
the InputCurrent() command over the SMBus. The total
input current is the sum of the device supply current,
the charger input current, and the system load current.
The device supply current is minimal (6mA, max) in
comparison to the charger current and system load.
The total input current can be estimated as follows:
where ηis the efficiency of the DC-to-DC converter
(typically 85% to 95%).
The MAX1535B/MAX1535C/MAX1535D allow for a 16-
bit InputCurrent() command that translates to a 1mA
LSB and a 65.535A full-scale current using a 10mΩ
current-sense resistor (R1 in Figure 1). Equivalently, the
InputCurrent() value sets the voltage across CSSP and
CSSN inputs in 10µV per LSB increments. The
MAX1535B/MAX1535C/MAX1535D ignore the first 7
LSBs and uses the next 6 bits to control the input-cur-
rent DAC. The input-current range of the MAX1535B/
MAX1535C/MAX1535D is from 256mA to 11.004A. All
codes requesting input current above 11.004A result in
an input-current setting of 11.004A. All codes request-
ing input current between 1mA to 256mA result in an
input-current setting of 256mA. The default input-current-
limit setting at POR is 256mA. When choosing the current-
sense resistor R1, carefully calculate its power rating.
and the overall accuracy of the sense amplifier. Note that
the voltage drop across R1 contributes additional power
loss, which reduces efficiency.
System currents normally fluctuate as portions of the
system are powered up or put to sleep. Without input-
current regulation, the input source must be able to
deliver the maximum system current and the maximum
charger-input current. By using the input-current-limit
circuit, the output-current capability of the AC wall
adapter can be lowered, reducing system cost.
LDO RegulatorAn integrated low-dropout (LDO) linear regulator pro-
vides a 5.4V supply derived from DCIN, which can
deliver at least 10mA of load current. The LDO powers
the gate driver of the low-side n-channel MOSFET in the
DC-DC converter. See the MOSFET Driverssection.
The LDO also biases the 4.096V reference and most of
the control circuitry. Bypass LDO to GND with a 1µF
ceramic capacitor.
VDDSupplyThe VDDinput provides power to the SMBus interface
and the thermistor comparators. Connect VDDto LDO,
or apply an external supply to VDDto keep the SMBus
interface active while the supply to DCIN is removed.
Operating ConditionsTable 1 is a summary of the following four MAX1535B/
MAX1535C/MAX1535D operating states:AC present. When DCIN is greater than 7.5V, the AC
adapter is considered to be present. In this condi-
tion, both the LDO and REF function properly and
battery charging is allowed. The AC_PRESENT bit
(bit 15) in the ChargerStatus() register is set to 1.Power fail. When DCIN is less than 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, PDS turns off the input p-channel
MOSFET switch and the POWER_FAIL bit (bit 13) in
the ChargerStatus() register is set to 1.IVVINPUTLOADCHARGEBATTIN=+×()×()[]/η
OPERATING STATESINPUT
CONDITIONSAC PRESENTPOWER FAILBATTERYBATT UNDERVOLTAGEVDD UNDERVOLTAGE
DCINVDCIN > 7.5VVDCIN < VBATT +
0.3VXXX
THMXXVTHM < 0.91 × VDDXX
BATTXVBATT > VDCIN -
0.3VXVBATT < 2.5VX
VDDXXXXVDD < 2.5V
Table 1. Summary of Operating States= Don’t care.
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery ChargersLINEAR
REGULATORREFERENCE
LOGIC AND
DEAD TIME
DC-DC
CONVERTERLVC
LEVEL SHIFTER
LEVEL SHIFTER
DACI
DACS
DACV
SMBus
CSIP
CSIN
CSSP
CSSN
VMAX
BATT
CCV
CCI
CCS
SDA
SCL
PDS
PDL
DCIN
LDO
REF
ACIN
ACOK
SRC
DHI
DHIV
DLOV
DLO
PGND
REF/2
BATT
DCIN
CSI
LVC
ENABLE
DCINBATTGND
SRC
SRC-10V
SRC
1MΩ
1MΩ
MAX1535B
MAX1535C
MAX1535D
IMAX
INT
GMV
GMI
GMS
THM
VDD
THO
THC
THH
THU
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery ChargersBattery present. When THM is less than 91% of VDD,
the battery is considered to be present. The
MAX1535B/MAX1535C/MAX1535D use the THM pin to
detect whether 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.Battery undervoltage. When BATT is less than 2.5V,
the battery is considered to be in an undervoltage
state. This condition causes the charger to reduce its
current compliance to 128mA. The content of the
ChargeCurrent() register is unaffected. The input cur-
rent limit and the content of the InputCurrent() register
are unaffected by battery undervoltage condition.
When the BATT voltage exceeds 2.7V, normal charg-
ing resumes. ChargeVoltage() is unaffected and can
be set as low as 1.024V.
•VDDundervoltage. When VDDis less than 2.5V, the
VDDsupply is considered to be in an undervoltage
state. The SMBus interface does not respond to com-
mands. Coming out of the undervoltage condition, the
part is in its POR state. No charging occurs when VDD
is in the undervoltage state.
SMBus InterfaceThe MAX1535B/MAX1535C/MAX1535D receive control
inputs from the SMBus interface. The serial interface
complies with the SMBus protocols as documented in
System Management Bus Specification V1.1 and can be
www.sbs-forum.org. The charger func-
tionality complies with Intel/Duracell smart charger speci-
fications for a level 2 charger, as well as supporting input
current limit and power source selection functions.
The MAX1535B/MAX1535C/MAX1535D use the SMBus
Read-Word and Write-Word protocols (Figure 3) 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.
Preset to
0b0001001
D7 D0D15 D8ChargerMode() = 0x12
ChargeCurrent() = 0x14
ChargeVoltage() = 0x15
AlarmWarning() = 0x16
InputCurrent() = 0x3F
Preset to
0b0001001
Preset to
0b0001001
D7 D0D15 D8ChargerSpecInfo() =
0x11
ChargerStatus() =
0x13
ACKMSB LSB8 bits
ACKCOMMAND
BYTEMSB LSB7 bits
SLAVE
ADDRESSSMSB LSB8 bits
ACK
LOW
DATA
BYTEMSB LSB8 bits
ACK
HIGH
DATA
BYTEWrite-Word Format
b) Read-Word FormatLEGEND:
S = START CONDITION or REPEATED START CONDITIONP = Stop Condition
ACK = ACKNOWLEDGE (LOGIC LOW)NACK = NOTACKNOWLEDGE (LOGIC HIGH)= WRITE BIT (LOGIC LOW)R = READ BIT (LOGIC HIGH)
MASTER TO SLAVE
SLAVE TO MASTER
HIGH
DATA
BYTE
NACK8 bits1b
MSB LSB1
LOW
DATA
BYTE
ACK8 bits1b
MSB LSB0
SLAVE
ADDRESSR7 bits1b
MSB LSB1
ACK
COMMAND
BYTEACK8 bits1b
MSB LSB0
ACKSLAVE
ADDRESSW7 bits1b
MSB LSB0
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery ChargersThe MAX1535B/MAX1535C/MAX1535D are SMBus
slave devices and do not initiate communication on the
bus. It responds to the 7-bit address 0b0001001. In
addition, the MAX1535B/MAX1535C/MAX1535D have
two identification (ID) registers: a 16-bit device ID reg-
ister (0x0006), and a 16-bit manufacturer ID register
(0x004D).
The data input SDA and clock input SCL pins have
Schmitt-trigger inputs that can accommodate slow
edges; however, the rising and falling edges should still
be faster than 1µs and 300ns, respectively.
Communication starts with the master signaling the
beginning of a transmission with a START condition,
high. When the master has finished communicating
with the slave, the master issues a STOP condition,
which is a low-to-high transition on SDA, while SCL is
high. The bus is then free for another transmission.
Figures 4 and 5 show the timing diagram for signals on
the SMBus interface. The address byte, command
byte, and data byte are transmitted between the START
and STOP conditions. The SDA state is allowed to
change only while SCL is low, except for the START
and STOP conditions. Data is transmitted in 8-bit bytes
and is sampled on the rising edge of SCL. Nine clock
cycles are required to transfer each byte in or out of the
MAX1535B/MAX1535C/MAX1535D since either the
SMBCLKCDEFGHIJK
SMBDATA
tSU:STAtHD:STA
tLOWtHIGH
tSU:DATtHD:DATtHD:DATtSU:STOtBUF
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW M
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SMBDATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
Figure 4. SMBus Write Timing
SMBCLK
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVECDEFGHIJ
SMBDATA
tSU:STAtHD:STA
tLOWtHIGH
tSU:DATtHD:DATtSU:DATtSU:STOtBUF
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = ACKNOWLEDGE CLOCK PULSE
J = STOP CONDITION
K = NEW START CONDITION
Figure 5. SMBus Read Timing
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery Chargerscorrect byte during the ninth clock. The MAX1535B/
MAX1535C/MAX1535D support the charger commands
as described in Tables 2–9.
Battery-Charger CommandsThe MAX1535B/MAX1535C/MAX1535D support seven
battery charger commands that use either Write-Word
or Read-Word protocols, as summarized in Table 2.
ChargerSpec()The ChargerSpec() command uses the Read-Word pro-
tocol (Figure 3). The command code for ChargerSpec() is
0x11(0b00010001). Table 3 lists the functions of the data
bits (D0–D15). Bit 0 refers to the D0 bit in the Read-Word
protocol. The MAX1535B/MAX1535C/MAX1535D comply
with level 2 Smart-Battery Charger Specification Revision
1.1; therefore, the ChargerSpec() command returns
0x0002.
ChargerMode()The ChargerMode() command uses the Write-Word
protocol (Figure 3). The command code for
ChargerMode() is 0x12 (0b00010010). Table 4 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 3). The command code for
ChargerStatus() is 0x13 (0b00010011). Table 5
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 MAX1535B/
MAX1535C/MAX1535Ds’ 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 charge current or charge voltage.
ChargeCurrent() (POR: 0x0080)The ChargeCurrent() command uses the Write-Word
protocol (Figure 3). The command code for
ChargeCurrent() is 0x14 (0b00010100). The 16-bit
binary number formed by D15–D0 represents the
charge-current set point in milliamps. However, the res-
olution of the MAX1535B/MAX1535C/MAX1535D are
128mA in setting the charge current; bits D0–D6 are
ignored as shown in Table 6. The D13, D14, and D15
bits are also ignored. Figure 6 shows the mapping
between the charge-current set point and the
ChargeCurrent() code. All codes requesting charge
current above 8.064A result in a current overrange, lim-
iting the charging current to 8.064A. All codes request-
ing charge current between 1mA to 128mA result in a
current setting of 128mA. A 10mΩcurrent-sense resis-
tor (R2 in Figure 1) is required to achieve the correct
code/current scaling.
COMMANDCOMMAND NAMEREAD/WRITEDESCRIPTIONPOR STATESTATUS BITS AFFECTED0x11ChargerSpec()Read OnlyCharger specification0x0002N/A
0x12ChargerMode()Write OnlyCharger modeN/A
CHARGE_INHIBITED,
ALARM_INHIBITED,
THERMISTOR_HOT
0x13ChargerStatus()Read OnlyCharger statusN/AN/A
0x14ChargeCurrent()Write OnlyCharge-current setting0x0080CURRENT_NOT_REG,
CURRENT_OR
0x15ChargeVoltage()Write OnlyCharge-voltage setting0x4B00VOLTAGE_NOT_REG,
VOLTAGE_OR
0x16AlarmWarning()Write OnlyAlarm warningN/AN/A
0x3FInputCurrent()Write OnlyInput current-limit setting0x0080CURRENT_NOT_REG
0xFEManufacturerID()Read OnlyManufacturer ID0x004DN/A
Table 2. Battery-Charger Command Summary
MAX1535B/MAX1535C/MAX1535D
Highly Integrated Level 2 SMBus
Battery ChargersThe default charge-current setting at POR is 128mA.
Thus, the first time the MAX1535B/MAX1535C/
MAX1535D power up, the charge current is regulated
at 128mA. Anytime the battery is removed, the
ChargeCurrent() register returns to its POR state.
ChargeVoltage() (POR: 0x4B00)The ChargeVoltage() command uses the Write-Word
protocol (Figure 3). The command code for
ChargeVoltage() is 0x15 (0b00010101). The 16-bit
binary number formed by D15–D0 represents the
charge-voltage set point in millivolts. However, the res-
olution of the MAX1535B/MAX1535C/MAX1535D is
16mV in setting the charge voltage; the D0–D3 bits are
ignored as shown in Table 7. The D15 bit is also
ignored. Figure 7 shows the mapping between the
charge-voltage set point and the ChargeVoltage()
code. All codes requesting charge voltage greater than
19.200V result in a voltage overrange, limiting the
charge voltage to 19.200V. All codes requesting
charge voltage below 1024mV result in a voltage set
point of zero, which terminates charging.
The default charge-voltage setting at POR is 19.200V.
Thus, the first time a MAX1535B/MAX1535C/
MAX1535D powers up, the charge voltage is regulated
at 19.200V. Anytime the battery is removed, the
ChargeVoltage() register returns to its POR state.
AlarmWarning()The AlarmWarning() command uses the Write-Word pro-
tocol (Figure 3). The command code for AlarmWarning()
is 0x16 (0b00010110). AlarmWarning() sets the
ALARM_INHIBITED status bit in the MAX1535B/
MAX1535C/MAX1535D if D15, D14, D13, D12, or D11 of
the Write-Word protocol equals 1. Table 8 summarizes
the AlarmWarning() command’s function. The
ALARM_INHIBITED status bit remains set until the bat-
tery is removed, a ChargerMode() command is written
with the POR_RESET bit set, or new ChargeCurrent() and
ChargeVoltage() values are written. As long as
ALARM_INHIBITED = 1, the MAX1535B/MAX1535C/
MAX1535D switching regulator remains off.
InputCurrent() (POR: 0x0080)The InputCurrent() command uses the Write-Word pro-
tocol (Figure 3). The command code for InputCurrent()
is 0x3F (0b00111111). The 16-bit binary number
formed by D15–D0 represents the charge-current set
point in milliamps. However, the resolution of the
MAX1535B/MAX1535C/MAX1535D is 256mA in setting
the charge current; the D0–D6 bits are ignored as
shown in Table 9. The D13, D14, and D15 bits are also
ignored. Figure 8 shows the mapping between the
input-current set point and the InputCurrent() code. All
codes requesting input current greater than 11.004A
result in an input-current overrange, limiting the input
BITBIT NAMEDESCRIPTIONCHARGER_SPECReturns a zero for version 1.1CHARGER_SPECReturns a 1 for version 1.1CHARGER_SPECReturns a zero for version 1.1CHARGER_SPECReturns a zero for version 1.1SELECTOR_SUPPORTReturns a zero, indicating no smart-battery selector functionalityReservedReturns a zeroReservedReturns a zeroReservedReturns a zeroReservedReturns a zeroReservedReturns a zeroReservedReturns a zeroReservedReturns a zeroReservedReturns a zeroReservedReturns a zeroReservedReturns a zeroReservedReturns a zero
Table 3. ChargerSpec()Command: 0x11
