Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - battery management Charge management Li-Ion QSOP 28 Surface-mount

AVAILABLE

Functional Diagrams

Pin Configurations appear at end of data sheet.

Functional Diagrams continued at end of data sheet.

UCSP is a trademark of Maxim Integrated Products, Inc.

For pricing, delivery, and

ordering information, please contact Maxim Direct

at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.

EVALUATION KIT AVAILABLE

General Description

The MAX1737 is a switch-mode lithium-ion (Li+) battery

charger that charges one to four cells. It provides a

regulated charging current and a regulated voltage

with only a ±0.8% total voltage error at the battery ter-

minals. The external N-channel switch and synchronous

rectifier provide high efficiency over a wide input volt-

age range. A built-in safety timer automatically termi-

nates charging once the adjustable time limit has been

reached.

The MAX1737 regulates the voltage set point and charg-

ing current using two loops that work together to transi-

tion smoothly between voltage and current regulation. An

additional control loop monitors the total current drawn

from the input source to prevent overload of the input

supply, allowing the use of a low-cost wall adapter.

The per-cell battery voltage regulation limit is set

between +4.0V and +4.4V and can be set from one to

four by pin strapping. Battery temperature is monitored

by an external thermistor to prevent charging if the bat-

tery temperature is outside the acceptable range.

The MAX1737 is available in a space-saving 28-pin

QSOP package. Use the evaluation kit (MAX1737EVKIT)

to help reduce design time.

Applications

Features

♦ Stand-Alone Charger for Up to Four Li+ Cells

♦ ±0.8% Accurate Battery Regulation Voltage

♦ Low Dropout: 98% Duty Cycle

♦ Safely Precharges Near-Dead Cells

♦ Continuous Voltage and Temperature Monitoring

♦ <1µA Shutdown Battery Current

♦ Input Voltage Up to +28V

♦ Safety Timer Prevents Overcharging

♦ Input Current Limiting

♦ Space-Saving 28-Pin QSOP

♦ 300kHz PWM Oscillator Reduces Noise

♦ 90% Conversion Efficiency

Stand-Alone Switch-Mode

Lithium-Ion Battery-Charger Controller

GND

DCIN

CSSP

CSSN

BST

VLO

DLO

PGND

THM

BATT

FASTCHG

FULLCHG

FAULT

SHDN

OFF

TIMER2

TIMER1

Li+

BATTERY

1 TO 4

CELLS

CCI

CCV

CCS

VADJ

ISETIN

REF

ISETOUT

INPUT SUPPLY

CELL

DHI

SYSTEM

LOAD

MAX1737

19-1626; Rev 4; 9/07

PART

MAX1737EEI -40°C to +85°C

TEMP RANGE PIN-PACKAGE

28 QSOP

Typical Operating Circuit

DCIN

CSSP

CSSN

DHI

BST

FAULT

VLO

DLO

PGND

SHDN

FULLCHG

FASTCHG

TIMER2

TIMER1

CELL

CCI

CCS

CCV

VADJ

BATT

GND

REF

THM

ISETOUT

ISETIN

QSOP

TOP VIEW

MAX1737

Pin Configuration

Ordering Information

Notebook Computers

Hand-Held Instruments

Li+ Battery Packs

Desktop Cradle Chargers

MAX1737

Summary of content (18 pages)

PAGE 1
EVALUATION KIT AVAILABLE LE AVAILAB MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller General Description Features The MAX1737 is a switch-mode lithium-ion (Li+) battery charger that charges one to four cells. It provides a regulated charging current and a regulated voltage with only a ±0.8% total voltage error at the battery terminals. The external N-channel switch and synchronous rectifier provide high efficiency over a wide input voltage range.
PAGE 2
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller ABSOLUTE MAXIMUM RATINGS CSSP, CSSN, DCIN to GND ...................................-0.3V to +30V BST, DHI to GND....................................................-0.3V to +36V BST to LX..................................................................-0.3V to +6V DHI to LX ..........................................-0.3V to ((BST - LX) + 0.3V) LX to GND ...............................................-0.3V to (CSSN + 0.
PAGE 3
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VCSSN = VCSSP = +18V, SHDN = VL, CELL = GND, VBATT = VCS = +4.2V, VVADJ = VREF / 2, ISETIN = ISETOUT = REF, RTHM = 10kΩ, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 0.584 0.80 mS ERROR AMPLIFIERS CCV Amplifier Transconductance (Note 2) 4.15V < VBATT < 4.25V, VCCV = 2V 0.
PAGE 4
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VCSSN = VCSSP = +18V, SHDN = VL, CELL = GND, VBATT = VCS = +4.2V, VVADJ = VREF / 2, ISETIN = ISETOUT = REF, RTHM = 10kΩ, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS Top-Off Timer Temperature Measurement Frequency 1nF on TIMER1 and TIMER2 MIN TYP MAX UNITS 40.5 45 49.8 min 0.98 1.12 1.
PAGE 5
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller ELECTRICAL CHARACTERISTICS (Circuit of Figure 1, VDCIN = VCSSN = VCSSP = +18V, SHDN = VL, CELL = GND, VBATT = VCS = +4.2V, VVADJ = VREF / 2, ISETIN = ISETOUT = REF, RTHM = 10kΩ, TA = -40°C to +85°C, unless otherwise noted.) (Note 9) PARAMETER CONDITIONS MIN MAX UNITS SUPPLY AND REFERENCE DCIN Input Voltage Range VL Output Voltage 6.0V < VDCIN < 28V REF Output Voltage REF Line Regulation 6 28 V 5.1 5.7 V 4.166 4.
PAGE 6
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDCIN = VCSSN = VCSSP = +18V, SHDN = VL, CELL = GND, VBATT = VCS = +4.2V, VVADJ = VREF / 2, ISETIN = ISETOUT = REF, RTHM = 10kΩ, TA = -40°C to +85°C, unless otherwise noted.) (Note 9) PARAMETER CONDITIONS MIN TYP MAX UNITS CONTROL INPUTS/OUTPUTS SHDN Input Voltage High SHDN Input Voltage Low (Note 8) 1.4 V 0.
PAGE 7
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller Typical Operating Characteristics (Circuit of Figure 1, VDCIN = +18V, ISETIN = ISETOUT = REF, VVADJ = VREF / 2, TA = +25°C, unless otherwise noted.) CHARGING CURRENT-SENSE VOLTAGE vs. ISETOUT VOLTAGE 2.5 2.0 1.5 1.0 0.5 150 125 100 75 50 25 80 60 40 20 0.5 1.0 1.5 2.0 0 0 2.5 CHARGING CURRENT (A) ISETOUT VOLTAGE (V) VOLTAGE LIMIT vs. VADJ VOLTAGE REFERENCE VOLTAGE vs. TEMPERATURE 4.40 4.30 4.25 4.20 4.15 4.
PAGE 8
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller Pin Description 8 PIN NAME FUNCTION 1 VL 2 ISETIN 3 ISETOUT 4 THM Thermistor Input. Connect a thermistor from THM to GND to set a qualification temperature range. If unused, connect a 10kΩ resistor from THM to ground. See Thermistor section. 5 REF 4.2V Reference Voltage Output. Bypass REF to GND with a 1µF or larger ceramic capacitor.
PAGE 9
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller Detailed Description The DC-DC converter uses an external dual N-channel MOSFET as a switch and a synchronous rectifier to convert the input voltage to the charging current or voltage. The typical application circuit is shown in Figure 1. Figure 2 shows a typical charging sequence and Figure 3 shows the block diagram. Charging current is set by the voltage at ISETOUT and the voltage across R18.
PAGE 10
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller FASTCHARGE STATE BATTERY CURRENT FULLCHARGE STATE TOP-OFF STATE DONE CHARGE I = 1C BATTERY VOLTAGE FASTCHG OUTPUT OPENDRAIN LOW FULLCHG OUTPUT OPENDRAIN LOW BATTERY INSERTION OR SHDN HIGH TRANSITION TO VOLTAGE MODE (APPROX 85% CHARGE) TOP-OFF TIMER TIMES OUT, END OF ALL CHARGE FUNCTIONS FULL-CHARGE TIMER TIMES OUT OR BATTERY CURRENT DROPS TO C/10 (APPROX 95% CHARGE) Figure 2.
PAGE 11
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller SHDN 160ns SLOPE COMP STOP SAW BATT BATT CS REF/42 5x CSI MAX1737 CCI GMI 3R ISETOUT R R/9 SW+ PREQ GND GATE CONTROL SWGND CSSP PWMCOMP 10x CSS CSSN CSCCI LVC 3R GMS ISETIN CCS GND REF/2.6 EA+ DHI ON CS+ BST DHI PWMCMP LX ILIMIT DLO LOWILIM OSC EA- LO VLO DLO PGND CCV R R REF/2 GND REF/42 R R/2 R/2 R/2 160ns ONE CELL PWMOSC TWO CELL THREE FOUR REF GND R VADJ 9R GMV CCV CCS R GND Figure 3.
PAGE 12
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller SHUTDOWN SHUTDOWN IS ENTERED FROM ALL STATES WHEN SHDN IS LOW. FASTCHG = HIGH FULLCHG = HIGH FAULT = HIGH VDCIN < BATT SHDN HIGH VBATT < UNDERVOLTAGE THRESHOLD VDCIN > VBATT RESET FASTCHG = HIGH FULLCHG = HIGH FAULT = HIGH PREQUAL FAULT PREQUAL TIMEOUT FASTCHG = LOW FULLCHG = HIGH FAULT = HIGH FASTCHG = HIGH FULLCHG = HIGH FAULT = LOW VBATT > 2.
PAGE 13
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller Table 1.
PAGE 14
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller The current-mode PWM controller uses the inductor current to regulate the output voltage or current, simplifying stabilization of the regulation loops. Separate compensation of the regulation circuits allows each to be optimally stabilized. Internal slope compensation is included, ensuring stable operation over a wide range of duty cycles.
PAGE 15
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller Design Procedure Setting the Battery Regulation Voltage VADJ sets the per-cell voltage limit. To set the VADJ voltage, use a resistor-divider from REF to GND. A GND-to-VREF change at VADJ results in a ±5% change in the battery limit voltage. Since the full VADJ range results in only a 10% change on the battery regulation voltage, the resistor-divider’s accuracy need not be as high as the output voltage accuracy.
PAGE 16
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller The maximum RMS input current occurs at 50% duty cycle, so the worst-case input ripple current is 0.5 × ICHG. If the input to output voltage ratio is such that the PWM controller will never work at 50% duty cycle, then the worst-case capacitor current will occur where the duty cycle is nearest 50%. The impedance of the input capacitor is critical to preventing AC currents from flowing back into the wall cube.
PAGE 17
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller For the high-side switch, the worst-case power dissipation due to on-resistance occurs at the minimum source voltage VDCIN(MIN) and the maximum battery voltage VBATT(MAX), and can be approximated by the equation: PR ≈ VBATT(MAX) VDCIN(MIN) × RDS(ON) × ICHG 2 VL and REF Bypassing The transition loss can be approximated by the equation: V × ICHG × f × t TR PT ≈ DCIN 3 where tTR is the MOSFET transition time.
PAGE 18
MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller Package Information QSOP.EPS (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH 21-0055 F 1 1 Note: The MAX1737EEI is a 28-pin QSOP and does not have a heat slug.