STAT Pin Boost Mode

High Impedance Mode

Output Inductor and Capacitance Selection Guidelines

OUT

OUT

1

=

o

2

L

C

f

p

´

´

(1)

Pre-Regulator Application

bq24150

bq24151

Protection in Boost Mode

Output Overvoltage Protection

The bq24150/1 provides a built-in overvoltage protection to protect the device and other components against

damage if the VBUS voltage goes too high. When an overvoltage condition is detected, the bq24150/1 turns off

the PWM converter, reset OPA_MODE bit to 0, sets fault status bits, and sends out fault pulse in STAT pin.

Once VBUS drops to the normal level, the boost starts after host sets OPA_MODE to "1", or the OTG pin

remains in active status.

Output Overload Protection

The bq24150/1 provides a built-in overload protection to prevent the device and battery from damage when

VBUS is over loaded. Once over load condition is detected, Q1 operates in linear mode to limit the output current

while VPMID keeps in voltage regulation. If the overload condition lasts for more than 30 ms, the overload fault is

detected. When an overload condition is detected, the bq24150/1 turns off the PWM converter, reset

OPA_MODE bit to 0, sets fault status bits, and sends out fault pulse in STAT pin. The boost will not start until the

host clears the fault register.

Battery Voltage Protection

fault status bits, and sends out fault pulse in STAT pin. Once battery voltage goes back to the normal level, the

boost starts after host sets OPA_MODE to "1", or the OTG pin remains in active status.

During normal boosting process, the STAT pin behaves as a high impedance (open-drain) output. Under fault

conditions, a 128-

µs pulse is sent out to notify the host.

When control bit of HZ-MODE is set to "1" and the OTG pin is not in active status, the bq24150/1 operates in

high impedance mode, with the impedance in VBUS pin higher than 165 k

Ω. In high impedance mode, a crude

not. If the crude 32 second timer expires, the bq24150/1 operates in 32 minute mode and the crude 32 second

timer is disabled. In 32 minute mode, when VBUS is below UVLO, the bq24150/1 operates in high impedance

mode regardless of the setting of the HZ_MODE bit.

The bq24150/1 provides internal loop compensation. With this scheme, the best stability occurs when the LC

To reduce the output voltage ripple, a ceramic capacitor with the capacitance between 4.7

µF and 47 µF is

Figure 2 shows a typical pre-regulator application that the bq24150/1 operates as a DC/DC converter, with the

termination disabled. The robust internal compensation design ensures the stable operation when the

host-controlled switch is turned off. With the input overvoltage protection, output current regulation and high

efficiency power conversion, the bq24150/1 is an ideal choice for pre-regulator used in pulse charging

applications.

Copyright © 2008, Texas Instruments Incorporated

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Product Folder Link(s): bq24150 bq24151