Document Number: 71321

S09-2249-Rev. C, 26-Oct-09

www.vishay.com

5

Vishay Siliconix

Si9731

Notes:

a. "OK to Charge" is a flag signal that is enabled by satisfying all the following conditions:

1. Battery voltage is below 5 V

2. Charger voltage is greater than 3 V but below 12.8 V

4. ON/OFF pin is at logic high.

b. Q1 drive is determined by the error amplifier during constant voltage mode.

Q1 drive is a combination of Q1 drive (digital) and the output of the error amplifier using the analog adder. The combinations are:

TABLE 1: BATTERY CHARGING CONTROL LOGIC Nominal Voltage Values

TRICKLE

CHARGEEN

CVMODE

MAIN

CHARGEEN

ON/OFF

Q2

Mode

Not Present

X

X

X

X

OFF

OFF

Not Charging

Not Present

X

X

X

X

OFF

OFF

Not Charging

Over Voltage

X

X

X

X

OFF

OFF

Not Charging

Present

X

X

X

LOW

OFF

OFF

Not Charging (Shutdown)

LOW

LOW

LOW

HIGH

OFF

ON

Trickle Charge

HIGH

LOW

LOW

HIGH

OFF

OFF

Not Charging

(Current pulse off during Constant

Current Charge)

LOW

LOW

HIGH

HIGH

ON

OFF

Constant Current Charge

(current pulse on)

HIGH

LOW

HIGH

HIGH

ON

OFF

LOW

HIGH

LOW

HIGH

OFF

OFF

Not Charging

(Current pulse off during Constant

Current Charge with output limited

to 4.1 V/4.2 V or end of charge in Li-Ion

charging)

HIGH

HIGH

LOW

HIGH

OFF

OFF

LOW

HIGH

HIGH

HIGH

ON

OFF

Constant Current Charge

(Output Limited to 4.1 V/4.2 V or

Constant Voltage Charge)

HIGH

HIGH

HIGH

HIGH

ON

OFF

TABLE 2

Q1 Drive (Digital)

Output of Error Amplifier

Q1 Drive

LOW

LOW

LOW (fully off)

LOW

Intermediate

Intermediate (linear mode)

HIGH

LOW

HIGH (fully on)

HIGH

HIGH

Should Never Happen