Start-Up Short-Circuit Protection

Enable Function

Fault Indication

bq24380

bq24381

The bq2438x features overload current protection during start-up. The condition 1 in Figure 18 illustrates start-up

into an overload condition. If after the eight soft-start steps are complete, and the current limit is exceeded, the IC

FAULT becomes high impedance and the soft-start sequence restarts. The device repeats the start/fail sequence

until the overload condition is removed. Once the overload condition is removed, the current limit circuitry is

disabled and the device enters normal operation. Additionally, if the current is not limited after the completion of

operation.

The IC has an enable pin which is used to enable and disable the device. Connect the CE pin high to turn off the

internal pass FET. Connect the CE pin low to turn on the internal pass FET and enter the start-up routine. The

CE pin has an internal pulldown resistor and can be left unconnected. The FAULT pin is high impedance when

the CE pin is high.

The FAULT pin is an active-low, open-drain output. It is in a high-impedance state when operating conditions are

safe, or when the device is disabled by setting CE high. With CE low, the FAULT pin goes low whenever any of

these events occurs:

1. Output short-circuit at power-on

2. Input overvoltage

3. Battery overvoltage

4. IC overtemperature

See Figure 18 for an example of FAULT conditions during these events. Connect the FAULT pin to the desired

logic level voltage rail through a resistor between 1 k

Ω and 50 kΩ.

10

Submit Documentation Feedback

Copyright © 2008, Texas Instruments Incorporated

Product Folder Link(s): bq24380 bq24381