4

LTC1729 Series

ELECTRICAL CHARACTERISTICS

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

AC CHARACTERISTICS

TIMER1

Timer for Trickle-Charge Preconditioning

q

0.869

1

1.305

Hr

TIMER2

Timer for Charging

q

2.61

3

3.55

Hr

TIMER3

q

0.764

0.859

1.043

sec

TIMER4

q

3.055

3.5

4.17

sec

Oscillator Period

q

6.66

7.63

9.09

µs

OVP (Pin 1): Output from an Internal Precision Resistor

Divider Used as a Voltage Feedback Monitor for Constant-

Voltage Mode Charging.

BAT (Pin 2): Input to Battery Monitor Circuits and OVP

Resistor Divider. The battery monitor circuits activate

trickle charge preconditioning, battery present detection

and C/10 current detection. This pin is in a high impedance

old. During trickle charge preconditioning and charging

the BAT pin sources 16mA and 1.3mA respectively. The

current sources are clamped from driving the BAT pin

above 4.5V/cell with an internal pull-down transistor.

In the No Bat, Done and Pause states or the Hold and Reset

modes, the current sources are turned off, leaving only the

55k OVP divider as a load on the BAT pin. Most chargers

have a 200

µA current source that will compensate for this

50

µA to 80µA load.

SENSE (Pin 3): Input to C/10 Current Detection Circuit.

This pin sinks 100

µAduringtheChargestatewhichisused

to program the C/10 current threshold.

GND (Pin 4): Ground.

NTC (Pin 5): Input to the NTC Thermistor Monitoring

Circuits. When the voltage on this pin is above 2.79V

(cold) or below 0.405V (hot), the state machine is locked

in the present state and the timer is stopped. This is called

the Hold mode. While in the Hold mode, the charger is

and SENSE pins are turned off. The STATUS pin is not

affected.

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

If the NTC pin is below 0.2V, the state machine is forced

in the reset mode with all the timers cleared to zero. The

current sources on the BAT pin and SENSE pin are

disabled leaving the 55k OVP divider. The STATUS pin is

pulled low in the Reset mode.

There is a 100

µA current source on the NTC pin to bias the

is greater than the undervoltage lockout threshold.

STATUS (Pin 6): Open-Drain Output for C/10 Charge

Termination Detection Circuit. When in the Charge state,

this pin is pulled low. Once the charge current drops below

the C/10 current threshold for three seconds, the pull-

down transistor is disabled, and a 50

µA pull-down current

sink remains activated until the 1- or 3-hour time-out or

the battery or wall adapter is removed.

When this pin is open circuit, the charger is active.

Normally this pin allows the charger to be active for three

hours.

tions, the undervoltage lockout is 10.4V with a minimum

undervoltage lockout and put the part in a high impedance

condition. When the supply is connected, the part is

initialized in the Reset mode with the state machine forced

in the Charge state with all the timers set to zero.

LTC1729-8.2/LTC1729-8.4