BQ24150 Datasheet, PDF (21/39 Pages) Texas Instruments – Fully Integrated Switch-Mode One-Cell Li-Ion Charger with Full USB Compliance and USB-OTG Support

bq24150
bq24151
www.ti.com ...................................................................................................................................................................................................... SLUS824 – JUNE 2008
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
During boosting, when battery voltage is above the battery overvoltage threshold, V_(BATMX), or below the minimum
battery voltage threshold, V_(BAT)min, 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 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.
STAT Pin Boost Mode
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.
High Impedance Mode
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 kΩ. In high impedance mode, a crude
32-second timer is enabled when the battery voltage is below V_(LOWV) to monitor the host control is available or
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.
Output Inductor and Capacitance Selection Guidelines
The bq24150/1 provides internal loop compensation. With this scheme, the best stability occurs when the LC
resonant frequency, ƒ_o, is approximately 40 kHz (20 kHz to 80 kHz). Equation 1 is used to calculate the value of
the output inductor, L_OUT, and output capacitor, C_OUT.
1
f_o =
2p ´ L_OUT ´ C_OUT
(1)
To reduce the output voltage ripple, a ceramic capacitor with the capacitance between 4.7 µF and 47 µF is
recommended for C_OUT, see the application section for components selection.
Pre-Regulator Application
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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