MAXIM MAX1758 User Manual

General Description

The MAX1758 is a switch-mode lithium-ion (Li+) battery charger that charges one-to-four cells. It provides a regulated charging current accurate to ±10% and a regulated voltage with only a ±0.8% total voltage error at the battery terminals. The internal high-side switch delivers a programmable current of up to 1.5A to charge the battery. The built-in safety timer automatically terminates charging once the adjustable time limit has been reached.

The MAX1758 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 (charging + system), and automatically reduces battery-charging current, preventing overload of the input supply and allowing the use of a low-cost wall adapter.

The per-cell battery regulation voltage is set between

4.0V and 4.4V using standard 1% resistors. The number of cells is set from 1-to-4 by pin strapping. Battery temperature is monitored by an external thermistor to prevent charging outside the acceptable temperature range.

The MAX1758 is available in a space-saving 28-pin SSOP package. Use the MAX1758EVKIT to help reduce design time. For a stand-alone charger with a 14V switch, refer to the MAX1757 data sheet. For a charger controller capable of up to 4A charging current, refer to the MAX1737 data sheet.

________________________Applications

Features

♦ Stand-Alone Charger for Up to 4 Li+ Batteries

♦ ±0.8% Battery Regulation Voltage Accuracy

♦ Low-Dropout 98% Duty Cycle

♦ Safely Precharges Near-Dead Cells

♦ Continuous Voltage and Temperature Monitoring

♦ 0.1µA Shutdown Battery Current

♦ Input Voltage Up to 28V

♦ Up to 1.5A Programmable Charge Current

♦ Safety Timer Prevents Overcharging

♦ Input Current Limiting

♦ Space-Saving 28-Pin SSOP

♦ 300kHz PWM Oscillator Reduces Noise

MAX1758

Stand-Alone, Switch-Mode

Li+ Battery Charger with Internal 28V Switch

________________________________________________________________ Maxim Integrated Products 1

19-1752; Rev 1; 1/01

EVALUATION KIT

AVAILABLE

Ordering Information

28 SSOP

PIN-PACKAGETEMP. RANGE

-40°C to +85°CMAX1758EAI

PART

Li+ Battery Packs Notebook Computers

Hand-Held Instruments Desktop Cradle Chargers

Pin Configuration

Typical Operating Circuit

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

TOP VIEW

ISETIN

ISETOUT

THM

REF

GND

VADJ

BATT

HSD

CELL

TIMER1

TIMER2

FAULT

DCIN

CSSP

CSSN

CCV

MAX1758

SSOP

CCI

CCS

BST

PGND

SHDN

FULLCHG

FASTCHG

6V TO 28V

OFF

REF

ISETOUT

ISETIN

CELL

VADJ

CCS

CCI

CCV

TIMER1

TIMER2

SHDN

DCIN

MAX1758

GND

CSSP

FASTCHG

FULLCHG

FAULT

CSSN

HSD

PGND

BATT

THM

SYSTEM LOAD

BST

THERM

Li+ BATTERY 1 TO 4 CELLS

MAX1758

Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 28V Switch

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, V

DCIN

= V

HSD

= V

CSSP

= V

CSSN

= 18V, V

SHDN

= VVL, V

CELL

= GND, V

BATT

= VCS= 4.2V, V

VADJ

= V

REF

/ 2,

ISETIN

= V

ISETOUT

= V

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.

DCIN, CSSP, CSSN, HSD to GND..........................-0.3V to +30V

CSSP to CSSN.......................................................-0.6V to +0.6V

BST to GND ............................................................-0.3V to +36V

BST to LX..................................................................-0.3V to +6V

LX to PGND ..............................................-0.6V to (V

HSD

+ 0.3V)

VL, SHDN, ISETIN, ISETOUT, REF, VADJ, CELL, TIMER1,

TIMER2, CCI, CCS, CCV, THM to GND ................-0.3V to +6V

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

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

CS to BATT Current ............................................................±3.5A

PGND to GND .......................................................-0.3V to +0.3V

VL Source Current...............................................................50mA

Continuous Power Dissipation (T

= +70°C)

28-Pin SSOP (derate 9.5mW/°C above +70°C) ...........762mW

Operating Temperature Range ...........................-40°C to +85°C

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

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

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

BATT

= 18V, done state

Falling edge

CELL = REF, V

BATT

= 15V, any charging state

SHDN

= GND, V

BATT

= 19V

6V < V

DCIN

< 28V

Internal resistor between CS and BATT,

1.5A RMS operating

See PWM Controller section

BST

= VLX+ 4.5V

VLX= V

HSD

= V

DCIN

=28V, V

SHDN

= GND

REF

= 0 to 1mA

VLX= PGND, V

HSD

= V

DCIN

= 28V,

SHDN

= GND

CSSN

= V

CSSP

= V

DCIN

= 28V, V

SHDN

= GND

6V < V

DCIN

< 28V

Rising edge

6V < V

DCIN

< 28V

IVL= 0 to 15mA

In-dropout, f

OSC

/ 4

6V < V

DCIN

< 28V

Nondropout f

OSC

CONDITIONS

µA150 270

BATT, CS Input Current

µA280 540

µA0.1 5

mΩ110 170R

CS to BATT Current-Sensing Resistance

Ω12LX to PGND On-Resistance

mΩ260 450HSD to LX On-Resistance

µA0.1 10LX Off-State Leakage

µA0.1 10HSD Off-State Leakage

µA210CSSN/CSSP Off-State Leakage

%97 98LX Maximum Duty Cycle

kHz270 300 330f

OSC

PWM Oscillator Frequency

V0.075 0.125 0.175

DCIN to BATT Dropout Threshold, DCIN Falling

mA57DCIN Quiescent Supply Current

mV614REF Load Regulation

mV26REF Line Regulation

V4.179 4.20 4.221

V0.20 0.30 0.40

DCIN to BATT Dropout Threshold, DCIN Rising

V5.10 5.40 5.70VL Output Voltage

mV44 65

REF

REF Output Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

V628DCIN Input Voltage Range

SUPPLY AND REFERENCE

SWITCHING REGULATOR

VL Output Load Regulation

MAX1758

Stand-Alone, Switch-Mode

Li+ Battery Charger with Internal 28V Switch

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V

DCIN

= V

HSD

= V

CSSP

= V

CSSN

= 18V, V

SHDN

= VVL, V

CELL

= GND, V

BATT

= VCS= 4.2V, V

VADJ

= V

REF

/ 2,

ISETIN

= V

ISETOUT

= V

REF

, R

THM

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

ADJ

= GND

Instantaneous peak current limit

With 1% VADJ resistors

Not including VADJ resistor tolerances

CELL = float, GND, VL, or REF

CONDITIONS

3.948 3.979 4.010

BATT Regulation Voltage Adjustment Range

-1 1

Absolute Voltage Accuracy %

-0.8 0.8

V/cell4.167 4.2 4.233V

BATTR

Battery Regulation Voltage

V019BATT, CS Input Voltage Range

A2.4 2.7 3.0CS to BATT Hard Current Limit

UNITSMIN TYP MAXSYMBOLPARAMETER

ADJ

= REF

V/cell

4.386 4.421 4.453

CCV

= 2V

mS ×

cells

0.4 0.7 1.0

CCV Amplifier Transconductance

CCV

= 2V µA±50

CCV Amplifier Maximum Output Current

A1.35 1.5 1.65BATT Full-Scale Charge Current

ISETOUT

= V

REF

/ 10 mA100 150 200

BATT 1/10-Scale Charge Current (Note 1)

BATT

< 2.4V per cell mA100 150 200

BATT Charge Current in Prequalification State

CCI

= 2V µA/A60 130 240CCI Battery Current Sense Gain

CCI

= 2V µA±100

CCI Amplifier Maximum Output Current

mV90 100 115

CSSP to CSSN Full-Scale Current-Sense Voltage

ISETIN

= V

REF

/ 10 mV51015

CSSP to CSSN 1/10-Scale Current-Sense Voltage

CCS

= 2V mS1.0 2.0 3.0CCS Amplifier Transconductance

mV25 200

CCV Clamp Voltage with Respect to CCI, CCS

THM low-temp or high-temp current V1.386 1.40 1.414V

TRT

THM Trip Threshold Voltage

THM

= 1.4V µA46.2 49 51.5I

TLTC

THM Low-Temp Current

THM

= 1.4V µA344 353 362I

THTC

THM High-Temp Current

Combines THM low-temp current and THM threshold, V

TRT

/ I

TLTC

kΩ26.92 28.70 30.59

THM COLD Threshold Resistance (Note 2)

Combines THM high-temp current and THM threshold, V

TRT

/ I

THTC

kΩ3.819 3.964 4.115

THM HOT Threshold Resistance (Note 2)

VOLTAGE LIMIT ACCURACY

ERROR AMPLIFIERS

STATE MACHINE

CCS

= 2V µA±100

CCS Amplifier Maximum Output Current

mV25 200

CCI, CCS Clamp Voltage with Respect to CCV

MAX1758

Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 28V Switch

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V

DCIN

= V

HSD

= V

CSSP

= V

CSSN

= 18V, V

SHDN

= VVL, V

CELL

= GND, V

BATT

= VCS= 4.2V, V

VADJ

= V

REF

/ 2,

ISETIN

= V

ISETOUT

= V

REF

, R

THM

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

CONDITIONS

% of

BATTR

x cell

94 95 96

BATT Recharge Voltage Threshold (Note 6)

mA250 330 400

FULLCHG BATT Current Termination Threshold (Note 5)

V/cell4.55 4.67 4.8

BATT Overvoltage Threshold (Note 4)

V/cell2.4 2.5 2.6

BATT Undervoltage Threshold (Note 3)

UNITSMIN TYP MAXSYMBOLPARAMETER

TIMER1 and TIMER2 Oscillation Frequency

2.1 2.33 2.6 kHz

Prequalification Timer 6.25 7.5 8.75

Fast-Charge Timer 81 90 100

Full-Charge Timer 81 90 100

Top-Off Timer 40.5 45 49.8

Temperature Measurement Frequency

0.98 1.12 1.32 Hz

SHDN Input Voltage High

1.4 V

SHDN Input Voltage Low

0.6 V

VADJ, ISETIN, ISETOUT Input Voltage Range

REF

VADJ

, V

ISETIN

, V

ISETOUT

= 0 or 4.2V nA

SHDN Input Bias Current

SHDN

= 0 or V

-1 1 µA

ISETOUT Shutdown Threshold Voltage (Note 3)

150 220 300 mV

CELL Input Bias Current V

CELL

= 0 or V

-5 5 µA

VADJ, ISETIN, ISETOUT Input Bias Current

CELL Input Voltage

For 1 cell 0 0.5

For 3 cells V

REF

- 0.3 V

REF

+ 0.3

For 2 cells (floating) 1.5 2.5

-50 50

CONTROL INPUTS/OUTPUTS

min

VVL- 0.4 V

For 4 cells

MAX1758

Stand-Alone, Switch-Mode

Li+ Battery Charger with Internal 28V Switch

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V

DCIN

= V

HSD

= V

CSSP

= V

CSSN

= 18V, V

SHDN

= VVL, V

CELL

= GND, V

BATT

= VCS= 4.2V, V

VADJ

= V

REF

/ 2,

ISETIN

= V

ISETOUT

= V

REF

, R

THM

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

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, V

DCIN

= V

HSD

= V

CSSP

= V

CSSN

= 18V, V

SHDN

= VVL, V

CELL

= GND, V

BATT

= VCS= 4.2V, V

VADJ

= V

REF

/ 2,

ISETIN

= V

ISETOUT

= V

REF

, R

THM

= 10kΩ, TA= -40°C to +85°C, unless otherwise noted.) (Note 7)

CONDITIONS

DCIN Input Voltage Range 628V

UNITSMIN TYP MAXSYMBOLPARAMETER

VL Output Voltage 5.1 5.7 V

REF Output Voltage 6V < V

DCIN

< 28V 4.166 4.242 V

REF Line Regulation 6V < V

DCIN

< 28V 6 mV

PWM Oscillator Frequency f

OSC

Nondropout f

OSC

260 340 kHz

HSD to LX On-Resistance V

BST

= VLX+ 4.5V 450 mΩ

LX to PGND On-Resistance 2 Ω

CS to BATT Hard Current Limit Instantaneous peak current limit 2.2 3.2 A

BATT, CS Input Voltage Range 019V

Absolute Voltage Accuracy

Not including VADJ resistor tolerances -0.8 0.8

With 1% VADJ resistors -1 1

CSSP to CSSN 1/10-Scale Current-Sense Voltage

SETIN

= V

REF

/ 10 515mV

THM Trip Threshold Voltage V

TRT

THM low- temp or high-temp current 1.386 1.414 V

THM Low-Temp Current I

TLTC

THM

= 1.4V 46.2 51.5 µA

FASTCHG

, V

FULLCHG

, V

FAULT

= 28V,

SHDN

= GND

SINK

= 5mA

CONDITIONS

µA1

FASTCHG, FULLCHG, FAULT Output High Leakage

V0.5V

FASTCHG, FULLCHG, FAULT Output Low Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

SUPPLY AND REFERENCE

SWITCHING REGULATOR

ACCURACY AND ERROR AMPLIFIERS

STATE MACHINE

BATT Regulation Voltage CELL = float, GND, VL, or REF 4.158 4.242 V/cell

BATT Full-Scale Charge Current 1.3 1.7 A

BATT 1/10-Scale Charge Current (Note 1)

SETOUT

= V

REF

/ 10 100 200 mA

BATT Charge Current in Prequalification State

BATT

< 2.4V per cell 100 200 mA

CSSP to CSSN Full-Scale Current-Sense Voltage

85 115 mV

250 400

MAX1758

Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 28V Switch

6 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V

DCIN

= V

HSD

= V

CSSP

= V

CSSN

= 18V, V

SHDN

= VVL, V

CELL

= GND, V

BATT

= VCS= 4.2V, V

VADJ

= V

REF

/ 2,

ISETIN

= V

ISETOUT

= V

REF

, R

THM

= 10kΩ, TA= -40°C to +85°C, unless otherwise noted.) (Note 7)

Note 1: When V

ISETOUT

= 0, battery charger turns off.

Note 2: See Thermistor section. Note 3: Below this threshold, charger reverts to a prequalification mode with I

BATT

reduced to 10% of full scale.

Note 4: Above this threshold, charger is disabled. Note 5: 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. See Table 1.

Note 6: After charging is complete, when BATT voltage falls below this threshold, a new charging cycle is initiated. Note 7: Specifications to -40°C are guaranteed by design, not production tested.

CONTROL INPUTS/OUTPUTS

V0.6V

SHDN Input Voltage Low

V1.4V

SHDN Input Voltage High

Hz0.93 1.37

Temperature Measurement Frequency

PARAMETER SYMBOL MIN TYP MAX UNITS

BATT Undervoltage Threshold (Note 3)

2.4 2.6 V/cell

BATT Overvoltage Threshold (Note 4)

4.55 4.8 V/cell

FULLCHG BATT Current Termination Threshold (Note 5)

CONDITIONS

CONTROL INPUTS/OUTPUTS

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