LM3655

Charge Control and Protection IC for embedded single

cell Li-Ion/Polymer batteries

1.0 General Description

The LM3655 provides complete charge control, discharge

control and battery safety of a single Lithium-Ion cell. It

supports battery charging by using a variety of power supply

types including unregulated current-limited wall adapters,

regulated wall adapters and vehicle power adapters. Charge

current control is achieved using an external bipolar PNP

power transistor.

Furthermore, the LM3655 provides effective and compre-

hensive discharge control functionality. All operating load

current is supplied by the Li-Ion battery and passes through

this IC. This allows the battery power to disconnect due to

overload, short-circuit or low battery conditions. The IC also

offers extensive battery safety protection against over-

voltage and over-current. The internal safety circuit is

backed up by an identical circuit to provide safety redun-

dancy. The LM3655 requires minimal external components

and is packaged in a micro surface mount device for inte-

gration in a single cell battery pack.

2.0 Key Specifications

n

1% precision pin-selectable nominal 4.10V and 4.16V

termination voltages

n

Up to 1.2A full-rate charge current

n

Safety Shunt voltage 4.35V

n

800 mW power regulation of external PNP at 25˚C

allows operation up to 30V (peak-to-peak) and 18V DC

3.0 Features

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Input over-voltage protection for load and battery pack

n

Input over-current protection for load and battery pack

n

Reverse current protection

n

Reverse charger protection

n

Input short circuit protection that protects the cell from a

short on the charger-connector

n

Output overload current and short circuit protection

n

Complete charge control with pre-charging for depleted

batteries, full-rate and trickle charging.

n

Support for charging with regulated and non-regulated

wall adapters and vehicle power adapters.

n

Power regulation of the external Power PNP

n

Chemistry selection for Li-ion and Li-polymer

n

Complete linear Peak detector function for filtering ripple

on input power supply

n

Digital filtering of the cell voltage transients during

transmit pulses when LM3655 is used in a battery pack

for cell phones.

n

25-pin, 2.5 mm x 2.5 mm microSMD package for

mounting on four layered PCB inside the battery pack.

4.0 Applications

n

Cell phones and other portable applications which use

embedded Li-ion batteries

5.0 Typical Application Circuit

20111501

Because the LM3655 and associated external components provide safety protection for both the Li-Ion cell and the phone circuitry, appropriate precautions

must be taken in system design and layout to ensure proper operation.

November 2004

© 2004 National Semiconductor Corporation

DS201115

www.national.com