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Timer Fault Recovery

Output Overvoltage Protection (Applies To All Versions)

Functional Description for System-Controlled Version (bq2411x)

Precharge And Fast-Charge Control

Charge Termination And Safety Timers

Inductor, Capacitor, and Sense Resistor Selection Guidelines

1

2p

L

OUT

C

OUT

(7)

bq24100, bq24103, bq24103A

bq24105, bq24108, bq24109

bq24113, bq24113A, bq24115

SLUS606K – JUNE 2004 – REVISED NOVEMBER 2007

As shown in FIGURE 10, bqSWITCHER provides a recovery method to deal with timer fault conditions. The

following summarizes this method.

Recovery method: bqSWITCHER waits for the battery voltage to fall below the recharge threshold. This could

happen as a result of a load on the battery, self-discharge or battery removal. Once the battery falls below the

recharge threshold, the bqSWITCHER clears the fault and enters the battery absent detection routine. A POR or

CE toggle also clears the fault.

to detect a battery removal condition and remains on as long as the battery voltage stays below the recharge

current and executes the recovery method described in Condition 1. Once the battery falls below the recharge

threshold, the bqSWITCHER clears the fault and enters the battery absent detection routine. A POR or CE toggle

also clears the fault.

The bqSWITCHER provides a built-in overvoltage protection to protect the device and other components against

damages if the battery voltage gets too high, as when the battery is suddenly removed. When an overvoltage

For applications requiring charge management under the host system control, the bqSWITCHER (bq2411x)

offers a number of control functions. The following section describes these functions.

A low-level signal on the CMODE pin forces the bqSWITCHER to charge at the precharge rate set on the ISET2

pin. A high-level signal forces charge at fast-charge rate as set by the ISET1 pin. If the battery reaches the

of the CMODE input.

The charge timers and termination are disabled in the system-controlled versions of the bqSWITCHER. The host

system can use the CE input to enable or disable charge. When an overvoltage condition is detected, the

charger process stops, and all power FETs are turned off.

The bqSWITCHER provides internal loop compensation. With this scheme, best stability occurs when LC

of the output inductor and capacitor. Table 3 provides a summary of typical component values for various charge

rates.

Table 3. Output Components Summary

CHARGE CURRENT

0.5 A

1 A

2 A

22

µH

10

µH

4.7

µH

4.7

µF

10

µF

22

µF (or 2 × 10 µH) ceramic

0.2

Ω

0.1

Ω

0.05

Ω

Copyright © 2004–2007, Texas Instruments Incorporated

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Product Folder Link(s): bq24100, bq24103, bq24103A bq24105, bq24108, bq24109 bq24113, bq24113A, bq24115