BQ25600 Datasheet, PDF (30/66 Pages) Texas Instruments – I2C Controlled 3.0-A, Single Cell Battery Charger With up-to 40-V Overvoltage Protection Controller for High-Input Voltage and Narrow Voltage DC (NVDC) Power Path Management

bq25600, bq25600D
SLUSCJ4 – JUNE 2017
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When a fault occurs, the charger device sends out INT and keeps the fault state in REG09 until the host reads
the fault register. Before the host reads REG09 and all the faults are cleared, the charger device would not send
any INT upon new faults. To read the current fault status, the host has to read REG09 two times consecutively.
The first read reports the pre-existing fault register status and the second read reports the current fault register
status.
7.3.10 Protections
7.3.10.1 Voltage and Current Monitoring in Converter Operation
The device closely monitors the input and system voltage, as well as internal FET currents for safe buck and
boost mode operation.
7.3.10.1.1 Voltage and Current Monitoring in Buck Mode
7.3.10.1.1.1 Input Overvoltage (ACOV)
This device integrates the functionality of an overvoltage protector. The device can be paired with an external N-
channel FET to block input voltages in excess of VBUS rating. For correct operation, connect the cathode of
body diode to VAC node. Back-to-back body diodes between VAC and VBUS are not recommended and will
prevent correct operation. The input voltage is sensed via the VAC pin and the ACDRV pin is used to control the
external FET gate for protection. The OVP threshold defaults to 6.2V, but can be programmed at 5.5V, 6.2V,
10.5V, or 14.3V via OVP register bits. The ACOV circuit has a reaction time of t_{AC_OV_FLT}. Note that turning off
the external OVPFET will take longer and depends on its gate capacitance. In addition to turning off the external
FET, an ACOV event will immediately stop switching whether in buck or boost mode.
During input overvoltage event (ACOV), the fault register CHRG_FAULT bits are set to 01. An INT pulse is
asserted to the host. The device will automatically resume normal operation once the input voltage drops back
below the OVP threshold.
7.3.10.1.1.2 System Overvoltage 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. SYSOVP threshold is 350 mV above minimum system regulation
voltage when the system is regulate at V_SYSMIN. Upon SYSOVP, converter stops switching immediately to clamp
the overshoot. The charger provides 30 mA discharge current to bring down the system voltage.
7.3.10.2 Voltage and Current Monitoring in Boost Mode
The device closely monitors the VBUS voltage, as well as RBFET and LSFET current to ensure safe boost mode
operation.
7.3.10.2.1 VBUS Soft Start
When the boost function is enabled, the device soft-starts boost mode to avoid inrush current.
7.3.10.2.2 VBUS Output Protection
The device monitors boost output voltage and other conditions to provide output short circuit and overvoltage
protection. The Boost build in accurate constant current regulation to allow OTG to adaptive to various types of
load. If short circuit is detected on VBUS, the Boost turns off and retry 7 times. If retries are not successful, OTG
is disabled with OTG_CONFIG bit cleared. In addition, the BOOST_FAULT bit is set and INT pulse is generated.
The BOOST_FAULT bit can be cleared by host by re-enabling boost mode
7.3.10.2.3 Boost Mode Overvoltage Protection
When the VBUS voltage rises above regulation target and exceeds VOTG_OVP, the device enters overvoltage
protection which stops switching, clears OTG_CONFIG bit and exits boost mode. At Boost overvoltage duration,
the fault register bit (BOOST_FAULT) is set high to indicate fault in boost operation. An INT is also asserted to
the host.
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