NJW4100

- 8 -

Ver.2005-01-20

1. Voltage Detection Block (VS pin)

The VS pin determines charge voltage, low voltage, over voltage, and re-charge voltage. Battery voltage conditions are

constantly monitored. (Figure 1)

1-1. Charge Voltage (VS pin)

2

B

2

B

1

B

R

R

R

+

Using the following settings makes it easy to support

If you use a high resistance, the VS pin's bias current will

cause incorrect values. Use as low a resistance as

possible.

1-2. Overcharge Detection Block (VS pin)

The overcharge detection block stops charging when a

high voltage is detected at the VS pin.

The overcharge detection voltage is obtained with the following equation:

When overcharge is detected, charging is prohibited and LED-R blinks. After that, charge will continue to be prohibited, even

after battery voltage drops to a normal value. Turning the power off to release UVLO, battery connection detection, or

CHG-SW switching will enable the charge sequence to restart.

1-3. Low Voltage Detection (2mA charge) Block (VS pin, CS1 pin)

The low voltage detection block detects an

over-discharged battery, or an open battery caused by

the battery protection circuit or the like. This will

determine a 2mA charge prior to pre-charging.

The low voltage detection voltage is obtained with the

following equation:

During a 2mA charge, the block monitors battery voltage

recovery while a steady 2mA current is output from the

CS1 pin. (Figure 2)

If voltage does not recover within a prescribed time, the

timer will prohibit 2mA charging. Turning the power off to

release UVLO, battery connection detection, or CHG-SW

switching will enable the charge sequence to restart.

1-4. Re-Charge Detection (VS pin)

When a fully charged battery is left for a long period of time, voltage will drop due to self-discharge. The re-charge detection

block detects a drop in voltage and re-charges the battery.

The re-charge detection voltage is obtained with the following equation.

Low Voltage

Detection

12dB

CS1

VS

Rcs

CS2

To Charge

Output

Control Block

2mA Charge

Current

To Charge Current

Control Amp

2mA Charge

VS

To Charge

Control Block

To OR

Circuit

Charge Voltage

Control Amp

CVCC-ON

Low Voltage

Detection

Over Voltage

Detection

Recharge

Detection

Quick Charge

Detection

Battery

Voltage

Detection

For 1 Cell

Figure 1. Voltage Detection Block Configuration

Figure 2. 2mA Charging Block