3

Lithium-Ion Battery Charger

TC3827

TC3827-2 12/12/00

© 2001 Microchip Technology Inc.

DS21558A

Pin No.

8-Pin MSOP

Symbol

Type

Description

1

SHDN

Signal Input

Shutdown Input

2

GND

Power

System Ground

3

MODE

Signal Output

Charge Mode Indicator

Voltage Output

Buffered Copy of Current Sense Resistor Drop

Voltage Input

Charger DC Output Voltage Sense

Signal Output

Gate Drive to External MOSFET

Signal Input

Current Sense Voltage Input

Power

Charger DC Input Voltage

PIN DESCRIPTION

FUNCTIONAL DESCRIPTION

The TC3827 controller only requires a P-channel power

MOSFET and two small capacitors to perform as an inex-

pensive Li-Ion battery charger. The TC3827 controller drives

an external PMOS to provide a regulated output current to

charge the battery. Initially, current limited charging occurs

pin. It then switches to constant-voltage mode. During

constant-voltage mode the TC3827 works like a linear

regulator, holding the output voltage within the specified

charging current follows the foldback characteristic as shown

in Figure 2. The sense resistor sets the maximum charging

sense voltage is provided as output on the current monitor

minimum voltage level, or if the battery is shorted, the

current sense circuit folds back the charge current to limit the

I/O DESCRIPTION

GND:

Connect to the battery’s negative terminal. See Layout Guidelines for information on system grounding.

Battery positive terminal and charger regulated output voltage.This pin is connected to the external PMOS drain

is removed. Requires a Bypass capacitor.

MODE: Charge Status Indicator. Mode is an open-drain, N-channel MOSFET capable of sinking

20mA for an LED status indication of charger in current limited mode. LED is off in current-voltage mode.

Gate drive output for the external PMOS pass device.

Battery Charge current profile. This output is an amplified copy of the voltage drop across the current sense resistor.

It can be used as input to an A/D converter to provide the controller with information about the charge current

profile.

Charger power supply input (+6V absolute max.). Bypass to GND with a capacitor.

Battery charge current sense voltage feedback. This voltage is developed across a small value precision resistor

that is in series with the battery.

of the IC need a suitable bypass capacitor. The TC3827 also

has a logic-level shutdown input, SHDN, which may be

connected to the input voltage to enable the IC. Pulling it

provided to drive an optional LED for a visual indication of

current limited mode operation. LED will be turned off in

constant voltage mode operation.