Single-Cell Li+ Battery Charger

for Current-Limited Supply

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5

0.9900

1.0000

0.9950

1.0100

1.0050

1.0150

1.0200

-40

20

40

-20

0

60

80

100

TIMER PERIOD vs.

AMBIENT TEMPERATURE

TEMPERATURE (°C)

NORMALIZED TO +25°C

Typical Operating Characteristics

4.0

4.8

4.4

4.6

4.2

5.2

5.0

5.8

5.6

5.4

6.0

515

10

20

25

PRECHARGE CURRENT

vs. INPUT VOLTAGE

0.9975

0.9985

0.9980

0.9995

0.9990

1.0010

1.0005

1.0000

1.0015

-40

0

-20

20

40

60

80

100

NORMALIZED BATT REGULATION VOLTAGE

vs. TEMPERATURE

TEMPERATURE (°C)

NORMALIZED TO +25°C

Pin Description

Battery Regulation Voltage Adjustment. Bypass to GND with a 1000pF capacitor. Connect a resistor from

ADJ to GND to reduce the nominal +4.200V regulation setpoint. See

Adjusting the Battery Regulation

Voltage.

ADJ

5

Ground. See

Layout Guidelines for information on system grounding. Connect the battery’s negative termi-

nal to GND.

GND

6

Thermistor Temperature-Sensor Input. Connect a thermistor from THERM to GND to prequalify the cell tem-

perature for fast-charge. Drive THERM high (> +1.4V) during Done or Fault states to reset the MAX1679 and

reinitiate the charging sequence. Replace the thermistor with a 10k

Ω resistor if temperature sensing is not

required.

THERM

7

Cell Voltage Monitor Input, Trickle-Charge Output, and MAX1679 Power Source. Connect BATT to the posi-

tive terminal of a single Li+ cell. Bypass BATT with a capacitor to ground (1.5µF per amp of charge current).

BATT

8

Maximum Total Charge-Time Selection. See Table 3 for timer options.

TSEL

4

Charge Status Indication. CHG is an open-drain, current-limited N-channel MOSFET suitable for directly dri-

ving an LED. Connect a pull-up resistor to BATT to generate a logic-level signal. See Table 2 for CHG out-

put states.

CHG

3

PIN

less. See

Selecting External Components.

GATE

2

Input Voltage from Current-Limited Voltage Source (+22V max). Bypass to GND with a 0.1µF capacitor. The

cell charging current is set by the current limit of the external power supply.

IN

1

FUNCTION

NAME