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High-Frequency,

Low-Cost SMBus Chargers

MAX17435/MAX17535

General Description

The MAX17435/MAX17535 integrated multichemistry

battery-charger ICs simplify construction of accurate

and efficient chargers. The MAX17435/MAX17535

provide SMBusK-programmable charge current, charge

voltage, input current limit, relearn voltage, and digital

readback of the IINP voltage. The MAX17435/MAX17535

utilize a charge pump to control the adapter selection

n-channel MOSFETs when the adapter is present. When

the adapter is absent, the charge pump is shut down and

a p-channel MOSFET selects the battery.

The MAX17435/MAX17535 provide up to 7A of charge

current to 2, 3, or 4 lithium-ion (Li+) cells in series. The

charge current, and input current-limit sense amplifiers have

low offset errors and can use 10mI sense resistors. The

MAX17435/MAX17535 fixed-inductor ripple architecture

significantly reduces component size and circuit cost.

The MAX17435/MAX17535 provide a digital output that

indicates the presence of the adapter, an analog output

that indicates the adapter or battery current, depending

upon the presence or absence of the adapter, and a

digital output that indicates when the adapter current

exceeds a user-defined threshold.

The MAX17435 switches at an 850kHz frequency and the

MAX17535 switches at 500kHz.

The MAX17435/MAX17535 are available in a small, 4mm

x 4mm x 0.75mm, 24-pin, lead-free TQFN package. An

evaluation kit is available.

Applications

Notebook Computers

PDAs and Mobile Communicators

2- to 4- Li+ Cell Battery-Powered Devices

Features

S Low-Cost SMBus Charger

High Switching Frequency (0.85MHz/0.5MHz)

Internal Boost Switches

SMBus-Programmable Charge Voltage, Input

Current Limit, Charge Current, Relearn Voltage,

and Digital IINP Readback

Single-Point Compensation

Automatic Selection of System Power Source

Adapter n-Channel MOSFETs Driven by an

Internal Dedicated Charge Pump

Adapter Soft-Start

±0.4% Accurate Charge Voltage

±2.5% Accurate Input Current Limiting

±3% Accurate Charge Current

Monitor Outputs for

AC Adapter Current (±2% Accuracy)

Battery Discharge Current (±2% Accuracy)

AC Adapter Presence

AC Adapter Overvoltage Protection

11-Bit Battery Voltage Setting

6-Bit, Charge-Current Setting/Input Current Setting

Improved IINP Accuracy at Low Input Current

Ordering Information

Pin Configuration

19-4817; Rev 1; 9/10

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

SMBus is a trademark of Intel Corp.

EVALUATION KIT

AVAILABLE

MAX17435

MAX17535

2 3 4 5 6

18 17 16 15 14 13

ACIN

ITHR

SCL

SDA

DCIN

LDO

DLO

ADAPTLIM

IINP

CSSN

PDSL

BATT

GND

CSIP

ACOK

CSIN

DHI

BST

CSSP

TOP VIEW

PART TEMP RANGE PIN-PACKAGE

MAX17435ETG+ -40

C to +85

C 24 TQFN-EP*

MAX17535ETG+ -40

C to +85

C 24 TQFN-EP*

Summary of content (28 pages)

PAGE 1
9-4817; Rev 1; 9/10 TION KIT EVALUA LE IL AVA AB High-Frequency, Low-Cost SMBus Chargers The MAX17435/MAX17535 are available in a small, 4mm x 4mm x 0.75mm, 24-pin, lead-free TQFN package. An evaluation kit is available. Applications Notebook Computers PDAs and Mobile Communicators S S S S Ordering Information PART TEMP RANGE PIN-PACKAGE MAX17435ETG+ -40NC +85NC 24 TQFN-EP* MAX17535ETG+ -40NC to +85NC 24 TQFN-EP* to +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad.
PAGE 2
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers ABSOLUTE MAXIMUM RATINGS CC, IINP to GND....................................... -0.3V to (VLDO + 0.3V) LDO Short Circuit to GND.......................................... Momentary Continuous Power Dissipation (TA = +70NC) 24-Pin TQFN (derate 20.8mW/NC above +70NC)........1666mW Operating Temperature Range........................... -40NC to +85NC Junction Temperature......................................................
PAGE 3
High-Frequency, Low-Cost SMBus Chargers (Circuit of Figure 1, no load on LDO, VDCIN = VCSSP = VCSSN = 19V, VLX = 0V, VBST - VLX = 5V, VBATT = VCSIP = VCSIN = 16.8V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 78.22 80.64 83.06 mV RS2 = 10mI, Figure 1, ChargingCurrent() = 0x1f80 7.822 8.064 8.306 A +3 % RS2 = 10mI, Figure 1, ChargingCurrent() = 0x0f80 3.
PAGE 4
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, no load on LDO, VDCIN = VCSSP = VCSSN = 19V, VLX = 0V, VBST - VLX = 5V, VBATT = VCSIP = VCSIN = 16.8V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL ACOK ACOK Sink Current CONDITIONS VACOK = 0.4V, VACIN = 2.5V MIN TYP MAX 1 UNITS mA 1 ACOK Leakage Current ACIN VACOK = 5.5V, VACIN = 0.
PAGE 5
High-Frequency, Low-Cost SMBus Chargers (Circuit of Figure 1, no load on LDO, VDCIN = VCSSP = VCSSN = 19V, VLX = 0V, VBST - VLX = 5V, VBATT = VCSIP = VCSIN = 16.8V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 2.04 2 2.1 V ADAPTER OVERVOLTAGE PROTECTION ACOVP Threshold Rising ACOVP Threshold Hysteresis 30 mV 144 mV 16 ms 0.
PAGE 6
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, no load on LDO, VDCIN = VCSSP = VCSSN = 19V, VLX = 0V, VBST - VLX = 5V, VBATT = VCSIP = VCSIN = 16.8V, TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MAX Adapter absent or charger shut down (Note 1) 1.5 VBATT = 2V to 19V, adapter present (Note 1) 650 VBATT = 16.
PAGE 7
High-Frequency, Low-Cost SMBus Chargers (Circuit of Figure 1, no load on LDO, VDCIN = VCSSP = VCSSN = 19V, VLX = 0V, VBST - VLX = 5V, VBATT = VCSIP = VCSIN = 16.8V, TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN MAX UNITS RS1 = 10mI, Figure 1, InputCurrent() = full scale 106.7 113.3 mV -2.5 +2.5 % RS1 = 10mI, Figure 1, InputCurrent() = 0C80 62.08 65.92 mV -3 +3 % RS1 = 10mI, Figure 1, InputCurrent() = 0780 36.86 39.
PAGE 8
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, no load on LDO, VDCIN = VCSSP = VCSSN = 19V, VLX = 0V, VBST - VLX = 5V, VBATT = VCSIP = VCSIN = 16.8V, TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN MAX UNITS 0.8 V LOGIC LEVELS SDA/SCL Input Low Voltage SDA/SCL Input High Voltage 2.
PAGE 9
High-Frequency, Low-Cost SMBus Chargers (Circuit of Figure 1, no load on LDO, VDCIN = VCSSP = VCSSN = 19V, VLX = 0V, VBST - VLX = 5V, VBATT = VCSIP = VCSIN = 16.8V, TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN MAX UNITS Hold Time from SCL tHD:DAT 300 ns Setup Time from SCL tSU:DAT 250 ns SCL Low Period tLOW 4.
PAGE 10
Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = 19V, VCC = VDD = 5V, EN = VCC, TA = +25NC, unless otherwise specified.) 2.0 1.5 1.0 VBATT = 16.8V 0.5 2.0 8 ICHARGER = 5A 1.5 ICHARGER = 3A 1.0 ICHARGER = 4A 0.5 0 0 VBATT = 8.4V VBATT = 12.6V 1 2 6 5 4 3 2 1 -0.5 0 3 4 3 7 8 13 18 2 6 4 SYSTEM CURRENT (A) BATTERY VOLTAGE (V) INPUT CURRENT-LIMIT SETTING (A) CHARGE VOLTAGE ACCURACY AT 3.854A CHARGER VOLTAGE ERROR vs.
PAGE 11
High-Frequency, Low-Cost SMBus Chargers (Circuit of Figure 1, VIN = 19V, VCC = VDD = 5V, EN = VCC, TA = +25NC, unless otherwise specified.) LDO VOLTAGE vs. LDO CURRENT VAA DEVIATION, SWITCHING AND NOT SWITCHING 5.44 5.42 5.40 0 SWITCHING -0.5 NOT SWITCHING 0 10 20 30 40 50 4.105 4.100 4.095 4.090 4.085 -1.5 5.34 MAX17435 toc15 MAX17435 toc14 0.5 -1.0 5.36 4.110 VAA VOLTAGE (V) 1.0 5.38 4.080 -2.
PAGE 12
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers Pin Description PIN NAME 1 SCL SMBus Clock Input. Connect to an external pullup resistor according to SMBus specifications. FUNCTION 2 SDA SMBus Data I/O. Open-drain output. Connect to an external pullup resistor according to SMBus specifications. 3 DCIN Charger Supply Input. Connect to adapter supply. For minimum input bias current connect to the center of the input/soft-start FETs.
PAGE 13
High-Frequency, Low-Cost SMBus Chargers PIN NAME FUNCTION 16 CSSP Current Sense for Positive Input. Connect a current-sense resistor from CSSP to CSSN. The voltage across CSSP to CSSN determines the current at which the charger reduces charging current to keep from drawing more current from the adapter than is allowed. As the system current flowing in the resistor from CSSN to CSSP increases, the charger reduces charge current to keep the system current at the limit value.
PAGE 14
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers Q1B R9 103kI R11 2MI RS1 10mI Q1A N3 ADAPTER R4 150kI C6 10nF R17 10I SYSTEM LOAD R18 1kI CIN N4 C10 1FF GND DCIN PDSL CSSP ACIN CSSN BST DHI R10 10kI C4 0.1FF LX DLO C1 1FF R16 10I R14 10kI L1 PGND PAD R5 10kI R13 10kI N2 ACOK ACOK LDO C IN = 2 x 4.7FF C OUT = 4.7FF L1 = 2FH N1 LDO MAX17435 MAX17535 RS2 10mI CSIP CSIN BATT VAA C3 1FF C11 1FF CC GND IINP VCC BATTERY IINP VOLTAGE C2 0.
PAGE 15
High-Frequency, Low-Cost SMBus Chargers LDO DHI BST DCIN PGND (PAD) LDO ADAPTER PRESENT 5.4V REGULATOR DLO LX LOW-SIDE DRIVER HIGH-SIDE DRIVER CSIN CSSP A = 20V/V CURRENTSENSE AMPLIFIER BATTERY CSSN GMS DCIN VAA GND CSIP 4.096V REFERENCE BATTERY OVP CHARGE VOLTAGE() 400mV IN_SET MAX17435 MAX17535 ZCMP AC_EN gMI CURRENTSENSE AMPLIFIER EN DC-DC CONVERTER IMAX CSI CCMP IMIN 750mA 8.
PAGE 16
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers Table 1. EN Pin Function ADAPTER PRESENT EN PDSL STATUS CHARGER STATUS SYSTEM CURRENT MONITOR STATUS (IINP PATH) Yes High PDSL is pumped 8V above the DCIN voltage (charge pump on). Enabled Enabled Yes Low PDSL is pumped 8V above the DCIN voltage (charge pump on). Disabled Enabled No High Charge pump is off and PDSL is forced to 0V (typ, 27C). Disabled Enabled No Low Charge pump is off and PDSL is forced to 0V (typ, 27C).
PAGE 17
High-Frequency, Low-Cost SMBus Chargers The address byte, command byte, and data bytes 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.
PAGE 18
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers A tLOW B C tHIGH D E F G H J I K SMBCLK SMBDATA tSU:STA tHD:STA tSU:DAT A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE tHD:DAT 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 tSU:STO tSU:DAT tBUF I = ACKNOWLEDGE CLOCK PULSE J = STOP CONDITION K = NEW STA
PAGE 19
High-Frequency, Low-Cost SMBus Chargers BIT BIT NAME 0 — Not used. Normally a 1mV weight. DESCRIPTION 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, 4095mV min. 1 = Adds 16mV of charger voltage compliance. 5 Charge Voltage, DACV 1 0 = Adds 0mV of charger voltage compliance, 4095mV min. 1 = Adds 32mV of charger voltage compliance.
PAGE 20
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers Table 5. ChargeCurrent() (0x14) (10mI Sense Resistor, RS2) (continued) BIT BIT NAME DESCRIPTION 9 Charge Current, DACI 2 0 = Adds 0mA of charger current compliance. 1 = Adds 512mA of charger current compliance. 10 Charge Current, DACI 3 0 = Adds 0mA of charger current compliance. 1 = Adds 1024mA of charger current compliance. 11 Charge Current, DACI 4 0 = Adds 0mA of charger current compliance.
PAGE 21
High-Frequency, Low-Cost SMBus Chargers BIT BIT NAME DESCRIPTION 0 — Not used. Normally a 2mA weight. 1 — Not used. Normally a 4mA weight. 2 — Not used. Normally an 8mA weight. 3 — Not used. Normally a 16mA weight. 4 — Not used. Normally a 32mA weight. 5 — Not used. Normally a 64mA weight. 6 — Not used. Normally a 128mA weight. 7 Input Current, DACS 0 0 = Adds 0mA of input current compliance. 1 = Adds 256mA of input current compliance.
PAGE 22
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers Table 7. Relearn() (0x3D) (continued) BIT BIT NAME DESCRIPTION 9 Relearn, RL 6 0 = Adds 0mV of relearn threshold compliance, 1024mV min. 1 = Adds 512mV of relearn threshold compliance. 10 Relearn, RL 7 0 = Adds 0mA of relearn threshold compliance. 1 = Adds 1024mV of relearn threshold compliance. 11 Relearn, RL 8 0 = Adds 0mV of relearn threshold compliance. 1 = Adds 2048mV of relearn threshold compliance.
PAGE 23
High-Frequency, Low-Cost SMBus Chargers BIT BIT NAME DESCRIPTION 10 IINP Voltage, DACV 6 0 = Adds 0mA of IINP voltage. 1 = Adds 828.8mV of IINP voltage. 11 IINP Voltage, DACV 7 0 = Adds 0mV of IINP voltage. 1 = Adds 1.6576V of IINP voltage to a maximum of 2.20V. 12 — Not used. Normally a 4096mV weight. 13 — Not used. Normally a 8192mV weight. 14 — Not used. Normally a 16384mV weight. 15 — Not used. Normally a 32768mV weight.
PAGE 24
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers controller to initiate a new cycle. If the peak inductor current exceeds IMAX comparator threshold or the output voltage exceeds the OVP threshold, then the on-time is terminated. The cycle-by-cycle current limit effectively protects against overcurrent and short-circuit faults. Under extremely light loads, the BST capacitor may become discharged if there is no DLO pulse.
PAGE 25
High-Frequency, Low-Cost SMBus Chargers Design Procedure MOSFET Selection Choose the n-channel MOSFETs according to the maximum required charge current. Low-current applications usually require less attention. The high-side MOSFET (N1) must be able to dissipate the resistive losses plus the switching losses at both VDCI(MIN) and VDCIN(MAX). Calculate both these sums. Ideally, the losses at VDCIN(MIN) should be roughly equal to losses at VDCIN(MAX) with lower losses in between.
PAGE 26
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers Inductor L1 must have a saturation current rating of at least the maximum charge current plus 1/2 the ripple current (DIL): ISAT = ICHG + (1/2) DIL The ripple current is determined by: DIL = VBATT O tOFF/L where: tOFF = 2.5Fs (VDCIN - VBATT)/ VDCIN for VBATT < 0.88 VDCIN or: tOFF = 0.3Fs for VBATT > 0.88 VDCIN Input Capacitor Selection The input capacitor must meet the ripple current requirement (IRMS) imposed by the switching currents.
PAGE 27
High-Frequency, Low-Cost SMBus Chargers 2) Place the IC and signal components. Keep the main switching node (LX node) away from sensitive analog components (current-sense traces and VAA capacitor). Important: The IC must be no further than 10mm from the current-sense resistors. Quiet connections to VAA, CC, ACIN, and DCIN should be returned to a separate ground (GND) island. The appropriate traces are marked on the schematic with the () ground symbol.
PAGE 28
MAX17435/MAX17535 High-Frequency, Low-Cost SMBus Chargers Revision History REVISION NUMBER REVISION DATE 0 7/09 Initial release 1 9/10 Removed the MAX17035 from the data sheet. DESCRIPTION PAGES CHANGED — 1–28 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.