BQ24150 Datasheet, PDF (20/39 Pages) Texas Instruments – Fully Integrated Switch-Mode One-Cell Li-Ion Charger with Full USB Compliance and USB-OTG Support

bq24150
bq24151
SLUS824 – JUNE 2008 ...................................................................................................................................................................................................... www.ti.com
OPA_MODE
0
1
X
Table 2. Operation Mode Summary
HZ_MODE
0
0
1
OPERATION MODE
Charge (no fault)
Charge configure (fault, V_bus > V_UVLO)
High impedance (V_bus < V_UVLO)
Boost (no faults)
Any fault go to charge configure mode
High impedance
Boost Mode Operation
In 32 second mode, when the OTG pin is in active status or the bit of operation mode (OPA_MODE) at control
register is set to 1, the bq24150/1 operates in boost mode and delivers the power to VBUS from the battery. At
normal boost mode, bq24150/1 converts the battery voltage (2.5 V to 4.5 V) to VBUS-B (about 5.05 V) and
delivers a current as much as I_(BO) (approximately 200 mA) to support other USB OTG devices connected to the
USB connector.
PWM Controller in Boost Mode
Similar to charge mode operation, in boost mode, the bq24150/1 provides an integrated, fixed 3 MHz frequency
voltage-mode controller to regulate output voltage at PMID pin (VPMID), as shown in Figure 22. The voltage
control loop is internally compensated using a Type-III compensation scheme that provides enough phase
margin for stable operation with a wide load range and battery voltage range
In boost mode, the input N-MOSFET (Q1) prevents battery discharge when VBUS pin is overloaded.
Cycle-by-cycle current limit is sensed through the internal sense MOSFET for Q3. The threshold for Q3 is set to
a nominal 1-A peak current. The upper-side MOSFET (Q2) also has a current limit that decides if the PWM
Controller will operate in synchronous or non-synchronous mode. This threshold is set to 75 mA and it turns off
the high-side N-channel MOSFET (Q2) before the current reverses, preventing the battery from charging.
Synchronous operation is used when the current of the high-side MOSFET is greater than 75 mA to minimize
power losses.
Boost Start Up
To prevent the inductor saturation and limit the inrush current, a soft-start control is applied during the boost start
up.
PFM Mode at Light Load
In boost mode, the bq2450/1 operates in pulse skipping mode (PFM mode) to reduce the power loss and
improve the converter efficiency at light load condition. During boosting, the PWM converter is turned off once
the inductor current is less than 75 mA; and the PWM is turned back on only when the voltage at PMID pin drops
to about 99.5% of the rated output voltage. A unique pre-set circuit is used to make the smooth transition
between PWM and PFM mode.
Safety Timer in Boost Mode
At the beginning of boost operation, the bq24150/1 starts a 32-second timer that can be reset by host through
I²C interface. Writing "1" to reset bit of TMR_RST in the control register resets the 32-second timer and
TMR_RST is automatically set to "0" after the 32-second timer is reset. To keep in boost mode, the host must
reset the 32-second timer repeatedly. Once the 32-second timer expires, the bq24150/1 turns off the boost
converter, enunciate the fault pulse in STAT pin and set fault status bits in status register. Fault condition is
cleared by POR or host control.
20
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