MAXIM MAX1737 User Manual

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 terminals. The external N-channel switch and synchronous rectifier provide high efficiency over a wide input voltage range. A built-in safety timer automatically terminates charging once the adjustable time limit has been reached.

The MAX1737 regulates the voltage set point and charging current using two loops that work together to transition 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 battery 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

MAX1737

Stand-Alone Switch-Mode

Lithium-Ion Battery-Charger Controller

________________________________________________________________ Maxim Integrated Products 1

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 3; 5/05

PART

MAX1737EEI -40°C to +85°C

TEMP RANGE PIN-PACKAGE

28 QSOP

EVALUATION KIT

AVAILABLE

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

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.

MAX1737

Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, V

DCIN

= V

CSSN

= V

CSSP

= +18V, SHDN = VL, CELL = GND, V

BATT

= VCS= +4.2V, V

VADJ

= V

REF

/ 2, ISETIN =

ISETOUT = REF, R

THM

= 10kΩ, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

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.

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 + 0.3V)

FULLCHG, FASTCHG, FAULT to GND ..................-0.3V to +30V

VL, VLO, SHDN, CELL, TIMER1, TIMER2, CCI,

CCS, CCV, REF, ISETIN, ISETOUT, VADJ,

THM to GND ........................................................-0.3V to +6V

DLO to GND...............................................-0.3V to (VLO + 0.3V)

BATT, CS to GND ...................................................-0.3V to +20V

PGND to GND, CSSP to CSSN..............................-0.3V to +0.3V

VL to VLO ..............................................................-0.3V to +0.3V

VL Source 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

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

VREF Output Voltage

SWITCHING REGULATOR

SUPPLY AND REFERENCE

With 1% VADJ resistors

-1 +1

Absolute Voltage Accuracy

Not including VADJ resistor tolerances

-0.8 +0.8 %

VADJ

= REF

VADJ

= GND

4.386 4.421 4.453

PARAMETER CONDITIONS MIN TYP MAX UNITS

6.0V < V

DCIN

< 28V

SHDN = GND, V

BATT

= 19V

LX = V

DCIN

= 28V, SHDN = GND

REF

= 0 to 1mA

6V < V

DCIN

< 28V

CSSN

= V

CSSP

= V

DCIN

= 28V, SHDN = GND

In dropout f

OSC

/ 4, V

CCV

= 2.4V,

BATT

= 15V, CELL = VL

6.0V < V

DCIN

< 28V

BATT

= 15V, CELL = VL

IVL= 0 to 15mA

µA

0.1 5

BATT, CS Input Current

µA

0.1 10

LX Leakage

Ω

DHI, DLO On-Resistance

µA

210

CSSN + CSSP Off-State Leakage

97 98

LX Maximum Duty Cycle

kHz

270 300 330

PWM Oscillator Frequency

DCIN Quiescent Supply Current

628

DCIN Input Voltage Range

614

REF Load Regulation

REF Line Regulation

4.179 4.20 4.221

0.05 0.155

DCIN to BATT Undervoltage Threshold, DCIN Falling

0.19 0.40

DCIN to BATT Undervoltage Threshold, DCIN Rising

5.10 5.40 5.70

VL Output Voltage

44 65

VL Output Load Regulation

225 500

CELL = SHDN = VL, V

BATT

= 17V

BATT, CS Input Voltage Range

Battery Regulation Voltage (V

BATTR

) CELL = float, GND, VL, or REF (Note 1)

019

4.167 4.2 4.233

V/cell

Battery Regulation Voltage Adjustment Range

CCV

= 2V

3.948 3.979 4.010 V/cell

MAX1737

Stand-Alone Switch-Mode

Lithium-Ion Battery-Charger Controller

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V

DCIN

= V

CSSN

= V

CSSP

= +18V, SHDN = VL, CELL = GND, V

BATT

= VCS= +4.2V, V

VADJ

= V

REF

/ 2, ISETIN =

ISETOUT = REF, R

THM

= 10kΩ, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

Full-Charge Timer

81 90 100

min

Fast-Charge Timer

81 90 100

min

BATT Overvoltage Threshold (Note 5)

4.55 4.67 4.8

V/cell

BATT Charge Current Full-Charge Termination Threshold CS-BATT (Note 6)

35 44 55

BATT Recharge Voltage Threshold (Note 7)

94 95 96

% of

BATTR

TIMER1, TIMER2 Oscillation Frequency

2.1 2.33 2.6

kHz

Prequalification Timer

6.25 7.5 8.75

min

CCI, CCS Clamp Voltage with Respect to CCV

25 200

CCV Clamp Voltage with Respect to CCI, CCS

25 200

THM Trip-Threshold Voltage

1.386 1.4 1.414

THM Low-Temperature Current

46.2 49 51.5

µA

THM High-Temperature Current

344 353 362

µA

THM COLD Threshold Resistance (Note 3)

26.92 28.70 30.59

kΩ

THM HOT Threshold Resistance (Note 3)

3.819 3.964 4.115

kΩ

BATT Undervoltage Threshold (Note 4)

2.4 2.5 2.6

V/cell

THM low-temperature or high-temperature current

THM

= 1.4V

THM

= 1.4V

Combines THM low-temperature current and THM rising threshold, V

TRT/ITLTC

Combines THM high-temperature current and THM rising threshold, V

TRT/ITHTC

CCV Amplifier Transconductance (Note 2)

0.39 0.584 0.80

CCV Amplifier Maximum Output Current

±50

µA

CS to BATT Current-Sense Voltage

30 40 50

CS to BATT Full-Scale Current-Sense Voltage

185 200 215

CS to BATT Current-Sense Voltage When in Prequalification State

51015

CS to BATT Hard Current-Limit Voltage

355 385 415

CSSP to CSSN Current-Sense Voltage

10 20 30

CSSP to CSSN Full-Scale Current-Sense Voltage

90 105 115

CCI Amplifier Transconductance

0.6 1 1.4

CCI Amplifier Output Current

±100

µA

CCS Amplifier Transconductance

1.2 2 2.6

CCS Amplifier Output Current

±100

µA

4.15V < V

BATT

< 4.25V, V

CCV

= 2V

3.5V < V

BATT

< 5V, V

CCV

= 2V

ISETOUT

= V

REF

/ 5

BATT

= 3V to 17V, CELL = GND or VL

BATT

< 2.4V per cell

6V < V

CSSP

< 28V, V

ISETIN

= V

REF

/ 5,

CCS

= 2V

6V < V

CSSP

< 28V, V

CCS

= 2V

CCI

= 2V

VCS- V

BATT

= 0, 400mV

SET

= REF, V

CCS

= 2V

CSSP

- V

CSSN

= 0, 200mV

PARAMETER MIN TYP MAX UNITSCONDITIONS

STATE MACHINE

ERROR AMPLIFIERS

MAX1737

Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V

DCIN

= V

CSSN

= V

CSSP

= +18V, SHDN = VL, CELL = GND, V

BATT

= VCS= +4.2V, V

VADJ

= V

REF

/ 2, ISETIN =

ISETOUT = REF, R

THM

= 10kΩ, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

CELL Input Voltage

0 0.5

1.5 2.5

REF

- 0.3 V

REF

+ 0.3

VVL- 0.4 V

FASTCHG, FULLCHG, FAULT Output Low Voltage

0.5

FASTCHG, FULLCHG, FAULT Output High Leakage

µA

For 1 cell

For 2 cells

For 3 cells

For 4 cells

SINK

= 5mA

FASTCHG, FULLCHG, FAULT = 28V; SHDN = GND

Top-Off Timer

40.5 45 49.8

min

SHDN Input Voltage High

1.4

SHDN Input Voltage Low (Note 8)

0.6

VADJ, ISETIN, ISETOUT Input Voltage Range

REF

VADJ, ISETIN, ISETOUT Input Bias Current

-50 50

SHDN Input Bias Current

-1 1

µA

CELL Input Bias Current

-5 5

µA

ISETIN Adjustment Range

REF

/ 5 V

REF

ISETOUT Adjustment Range

REF

/ 5 V

REF

ISETOUT Voltage for I

CHG

= 0

150 220 300

VADJ

, V

ISETIN

, V

ISETOUT

= 0 or 4.2V

SHDN = GND or VL

PARAMETER MIN TYP MAX UNITSCONDITIONS

Temperature Measurement Frequency

0.98 1.12 1.32

Hz1nF on TIMER1 and TIMER2

CONTROL INPUTS/OUTPUTS

MAX1737

Stand-Alone Switch-Mode

Lithium-Ion Battery-Charger Controller

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, V

DCIN

= V

CSSN

= V

CSSP

= +18V, SHDN = VL, CELL = GND, V

BATT

= VCS= +4.2V, V

VADJ

= V

REF

/ 2, ISETIN =

ISETOUT = REF, R

THM

= 10kΩ, TA= -40°C to +85°C, unless otherwise noted.) (Note 9)

PARAMETER CONDITIONS MIN MAX UNITS

DCIN Input Voltage Range

VL Output Voltage

REF Output Voltage

REF Line Regulation

PWM Oscillator Frequency

DHI, DLO On-Resistance

BATT, CS Input Voltage Range

Battery Regulation Voltage (V

BATTR

)

Absolute Voltage Accuracy

CS to BATT Current-Sense Voltage

CS to BATT Full-Scale Current-Sense Voltage

CS to BATT Current-Sense Voltage When in Prequalification State

CS to BATT Hard Current-Limit Voltage

CSSP to CSSN Current-Sense Voltage

CSSP to CSSN Full-Scale Current-Sense Voltage

THM Trip-Threshold Voltage

THM Low-Temperature Current

THM COLD Threshold Resistance (Note 3)

BATT Undervoltage Threshold (Note 4)

BATT Overvoltage Threshold (Note 5)

BATT Charge Current Full-Charge Termination Threshold, CS-BATT (Note 6)

Temperature Measurement Frequency 1nF on TIMER1 and TIMER2

4.55 4.8 V/cell

35 55 mV

0.93 1.37 Hz

6.0V < V

DCIN

< 28V

6V < V

DCIN

< 28V

BATT

= 15V, CELL = VL

CELL = float, GND, VL, or REF

Not including V

ADJ

resistor tolerances

ISETOUT

= V

REF

BATT

= 3V to 17V, CELL = GND or VL

BATT

< 2.4V per cell

6V < V

CSSP

< 28V, V

ISETIN

= V

REF

/5,

CCS

= 2V

6V < V

CSSP

< 28V, V

CCS

= 2V

THM low-temperature or high-temperature current

THM

= 1.4V

Combines THM low-temperature current and THM rising threshold, V

TRT/ITLTC

260 340 kHz

6 mV

4.166 4.242 V

7 Ω

019V

4.158 4.242 V/cell

-1 1 %

628V

5.1 5.7 V

25 55 mV

180 220 mV

317mV

350 420 mV

535mV

85 115 mV

1.386 1.414 V

46.2 51.5 µA

26.92 30.59 kΩ

2.4 2.6 V/cell

SUPPLY AND REFERENCE

SWITCHING REGULATOR

ERROR AMPLIFIERS

STATE MACHINE

MAX1737

Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller

6 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V

DCIN

= V

CSSN

= V

CSSP

= +18V, SHDN = VL, CELL = GND, V

BATT

= VCS= +4.2V, V

VADJ

= V

REF

/ 2, ISETIN =

ISETOUT = REF, R

THM

= 10kΩ, TA= -40°C to +85°C, unless otherwise noted.) (Note 9)

Note 1: Battery Regulation Voltage = Number of Cells

× (3.979V + 0.10526 × V

VADJ

Note 2: This transconductance is for one cell. Divide by number of cells to determine actual transconductance. Note 3: See Thermistor section. Note 4: Below this threshold, the charger reverts to prequalification mode and I

CHG

is reduced to about 5% of full scale.

Note 5: Above this threshold, the charger returns to reset. Note 6: After full-charge state is complete and peak inductor current falls below this threshold, FULLCHG output switches high.

Battery charging continues until top-off timeout occurs.

Note 7: After charging is complete, when BATT voltage falls below this threshold, a new charging cycle is initiated. Note 8: In shutdown, charging ceases and battery drain current drops to 5µ A ( max), but internal IC bias current remains on. Note 9: Specifications to -40°C are guaranteed by design and not production tested.

SHDN Input Voltage Low (Note 8)

0.6

SHDN Input Voltage High

1.4 V

PARAMETER MIN TYP MAX UNITSCONDITIONS

CONTROL INPUTS/OUTPUTS

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