BQ24298_15 Datasheet, PDF (25/51 Pages) Texas Instruments – bq24298 I2C Controlled 3A Single Cell USB Charger With Narrow VDC Power Path Management and Adjustable Voltage USB OTG

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bq24298
SLUSC59 – APRIL 2015
8.3.5.3.2 System Over-Voltage Protection (SYSOVP)
The charger device clamps the system voltage during load transient so that the components connect to system
would not be damaged due to high voltage. When SYSOVP is detected, the converter stops immediately to
clamp the overshoot.
8.3.5.4 Voltage and Current Monitoring in Boost Mode
The charger device closely monitors the VBUS voltage, as well as HSFET current to ensure safe boost mode
operation.
8.3.5.4.1 Over-Current Protection
The charger device closely monitors the RBFET (Q1) and LSFET (Q3) current to ensure safe boost mode
operation. During over-current condition,
1. If the over-current condition is not severe, the device will operate in hiccup mode for protection. While in
hiccup mode cycle, the device turns off RBFET for t_{OTG_OCP_OFF} (32 ms typical) and turns on RBFET for
t_{OTG_OCP_ON} (260 µs typical) in an attempt to restart. If the over-current condition is removed, the boost
converter will maintain the RBFET on state and the VBUS OTG output will operate normally. When over-
current condition continues to exist, the device will repeat the hiccup cycle until over-current condition is
removed.
2. If the over-current condition is severe, the device will shut down the RBFET (Q1) and reset all the registers.
When over-current condition is detected, the fault register bit BOOST_FAULT (REG09[6]) is set high to indicate
fault in boost operation. An INT is asserted to the host.
8.3.5.4.2 VBUS Over-Voltage Protection
When an adapter plugs in during boost mode, the VBUS voltage will rise above regulation target. Once the
VBUS voltage exceeds V_{OTG_OVP}, the device stops switching and the device exits boost mode. During the over-
voltage, the fault register bit BOOST_FAULT (REG09[6]) is set high to indicate fault in boost operation. An INT is
asserted to the host.
8.3.5.4.3 Output Short Protection
In addition, the device monitors BATFET current to provide short protection. The OTG mode is turned off and
OTG_CONFIG bit is cleared when output short is detected. The host can re-enable OTG mode by setting
OTG_CONFIG bit and OTG pin high.
8.3.5.5 Battery Protection
8.3.5.5.1 Battery Over-Voltage Protection (BATOVP)
The battery over-voltage limit is clamped at V_{BAT_OVP} (4% nominal) above the battery regulation voltage. When
battery over voltage occurs, the charger device immediately disables charge. The fault register REG09[3] goes
high and an INT is asserted to the host.
8.3.5.5.2 Battery Short Protection
If the battery voltage falls below V_short (2V typical), the device immediately turns off BATFET to disable the
battery charging or supplement mode. 1ms later, the BATFET turns on and charge the battery with 100-mA
current. The device does not turn on BATFET to discharge a battery that is below 2.5 V.
8.4 Device Functional Modes
8.4.1 Host Mode and Default Mode
The device is a host controlled device, but it can operate in default mode without host management. In default
mode, the device can be used as an autonomous charger with no host or with host in sleep.
Copyright © 2015, Texas Instruments Incorporated
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