Features

• Complete Pulse Charger for 1-Cell Lithium-Ion Batteries
• Sense Resistor Limits Maximum Current for Safety
• 1% Float Voltage Accuracy
• End-of-Charge (C/10) Detection Output
• Programmable Charge Termination Timer
• Internal 0.35 Ohm 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 Is Removed
• Battery Temperature Sensing and Charge Qualification
• Automatic Trickle Charge for Low-Battery Cell
• Automatic Battery Refresh

Typical Application

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 programmed voltage, the internal MOSFET begins switching off and on with the duty cycle gradually decreasing as the battery approaches a fully charged condition. A programmable 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 1µA (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, eliminating 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.