BQ25895_16 Datasheet, PDF (28/67 Pages) Texas Instruments – Adjustable Voltage 3.1-A Boost Operation

bq25895
SLUSC88A – MARCH 2015 – REVISED MAY 2016
www.ti.com
During thermal regulation, the actual charging current is usually below the programmed battery charging current.
Therefore, termination is disabled, the safety timer runs at half the clock rate, and the status register
THERM_STAT bit goes high.
Additionally, the device has thermal shutdown to turn off the converter and BATFET when IC surface
temperature exceeds T_SHUT. The fault register CHRG_FAULT is set to 10 and an INT is asserted to the host. The
BATFET and converter is enabled to recover when IC temperature is below T_{SHUT_HYS}.
8.2.13.0.2 Thermal Protection in Boost Mode
The device monitors the internal junction temperature to provide thermal shutdown during boost mode. When IC
surface temperature exceeds T_SHUT, BATFET is turned off to disable battery discharge. When IC surface
temperature is below T_{SHUT_HYS}, the host can use one of the method describes in section BATFET Enable (Exit
Shipping Mode) to recover.
8.2.14 Voltage and Current Monitoring in Buck and Boost Mode
8.2.14.1 Voltage and Current Monitoring in Buck Mode
The device closely monitors the input and system voltage, as well as HSFET current for safe buck and boost
mode operations.
8.2.14.1.1 Input Overvoltage (ACOV)
The input voltage for buck mode operation is V_{VBUS_OP}. If VBUS voltage exceeds V_ACOV, the device stops
switching immediately. During input over voltage (ACOV), the fault register CHRG_FAULT bits sets to 01. An INT
is asserted to the host..
8.2.14.1.2 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. When SYSOVP is detected, the converter stops immediately to
clamp the overshoot.
8.2.14.2 Current Monitoring in Boost Mode
The device closely monitors the VBUS voltage, as well as LSFET current to ensure safe boost mode operation.
8.2.14.2.1 Boost Mode Overvoltage Protection
When PMID voltage rises above regulation target and exceeds V_{OTG_OVP}, the device enters overvoltage
protection which stops switching and pauses boost mode (OTG_CONFIG bit remains set) until OVP fault is
removed. During the overvoltage, the fault register bit (BOOST_FAULT) is set high to indicate fault in boost
operation. An INT is also asserted to the host.
8.2.15 Battery Protection
8.2.15.1 Battery Overvoltage Protection (BATOVP)
The battery overvoltage limit is clamped at 4% above the battery regulation voltage. When battery over voltage
occurs, the charger device immediately disables charge. The fault register BAT_FAULT bit goes high and an INT
is asserted to the host.
8.2.15.2 Battery Over-Discharge Protection
When battery is discharged below V_{BAT_DPL}, the BAe batterTFET is turned off to protect battery from over
discharge. To recover from over-discharge, an input source is required at VBUS. When an input source is
plugged in, the BATFET turns on. Thy is charged with I_BATSHORT (typically 100 mA) current when the VBAT <
V_SHORT, or precharge current as set in IPRECHG register when the battery voltage is between V_SHORT and
V_BATLOWV.
28
Submit Documentation Feedback
Product Folder Links: bq25895
Copyright © 2015–2016, Texas Instruments Incorporated