LTC1730-4

Features:

Complete Pulse Charger for 1-Cell Lithium-IonBatteries
Sense Resistor Limits Maximum Current for Safety
1% Float Voltage Accuracy
End-of-Charge (C/10) Detection Output
Programmable Charge Termination Timer
Internal 0.35Ω NMOS Switch
No Blocking Diode Required
SEL Pin to Set Either 4.1V or 4.2V/Cell (LTC1730-4)
Low-Battery Drain (1µA Max) when Input Supply IsRemoved
Battery Temperature Sensing and ChargeQualification
Automatic Trickle Charge for Low-Battery
Automatic Battery Refresh


Application

Standalone Lithium-Ion Battery Charger
Handheld Computers
Cellular Telephones


Pinout




Specifications

Supply Voltage (V_CC)............................................13.2V
SENSE, GATE, BAT,
TIMER, NTC/SHDN, SEL............................0.3V to V_CC
CHRG, ACPR, FAULT..............................0.3V to 13.2V
Operating Junction
Temperature Range (Note 2)..................40°C to 85°C
Storage Temperature Range.................65°C to 150°C
Lead Temperature (Soldering, 10 sec)..................300°C

Description

The LTC®1730 is a complete pulse charger for 1-cell lithium-ion batteries. When charging a depleted cell, the internal MOSFET is fully on allowing the current limited input power source to provide charge current to the battery, virtually eliminating heat generation in the charger.

As the battery accepts charge and approaches the pro-grammed voltage, the internal MOSFET begins switching off and on with the duty cycle gradually decreasing as thebattery approaches a fully charged condition. A program-mable timer ends the charge cycle. The end-of-charge condition is indicated at the CHRG pin when the average charge current falls to C/10. Removing the input voltage puts the LTC1730 into a sleep mode, dropping the battery current drain to less than 1µ A (maximum).

An external sense resistor limits the maximum charge current as a safety precaution against a user connecting a wall adapter with the incorrect or no current limit. The internal MOSFET prevents reverse battery current from flowing if the input voltage is shorted to ground, eliminat-ing the need for a blocking diode.

The LTC1730-4 is available in the 16-pin SSOP package and the LTC1730-4.2 is available in the 8-pin SO package.