LTC4095

7

4095fa

SIMPLIFIED BLOCK DIAGRAM

–

+

6

+

–

RECHRG

CHRGR

ON

TEMP

FAULT

TERMINATE

CHARGE

BAD

BAT

TRICKLE

2.9V

M1

BAT

4.105V

NTC

3

CHRG

NTC

TRICKLE

CHARGE

TEMP FAULT

CONTROL

LOGIC

BLINK

LOGIC

COUNTER

2.25MHz CLOCK

CONSTANT CURRENT/

CONSTANT VOLTAGE

CHARGE

CURRENT

CONTROL

RECHARGE

–

+

C/10

100mV

PROG

ENABLE

800

HPWR

5

IN

THERMAL

AMP

BAT

BAT

IN

4V

8

1

–

+

SUSP

4095 F01

4

7

GND

2

IN

DUVLO

UVLO

Figure 1. LTC4095 Block Diagram

OPERATION

Introduction

The LTC4095 is a linear battery charger designed to

charge single-cell lithium-ion batteries. The charger uses

a constant-current/constant-voltage charge algorithm

with a charge current programmable up to 950mA. Ad-

ditional features include automatic recharge, an internal

termination timer, low-battery trickle charge conditioning,

bad-battery detection, and a thermistor sensor input for

out of temperature charge pausing.

Futhermore, the LTC4095 is capable of operating from a

USB power source. In this application, charge current can

be programmed to a maximum of 100mA or 500mA per

USB power specifications.

Input Current vs Charge Current

The LTC4095 regulates the total current delivered to the

BAT pin; this is the charge current. To calculate the total

input current (i.e., the total current drawn from the IN pin),

it is necessary to sum the battery charge current, charger

quiescent current and PROG pin current.

Undervoltage Lockout (UVLO)

The undervoltage lockout circuit monitors the input volt-

age (IN) and disables the battery charger until IN rises

oscillations around the trip point. In addition, a differential

undervoltage lockout circuit disables the battery charger

BAT voltage.

Suspend Mode

The LTC4095 can also be disabled by pulling the SUSP

pin above 1.2V. In suspend mode, the battery drain cur-

rent is reduced to 1.3µA and the input current is reduced

to 8.5µA.