BQ25890H Datasheet, PDF (30/66 Pages) Texas Instruments – I2C Controlled Single Cell 5-A Fast Charger

BQ25890H
SLUSCC5 – SEPTEMBER 2016
www.ti.com
8.2.15.1.2 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.
8.2.15.2 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.
8.2.15.2.1 VBUS Overcurrent Protection
The charger device closely monitors the RBFET (Q1), and LSFET (Q3) current to ensure safe boost ode
operation. During overcurrent condition when output current exceed (I_{OTG_OCP}) the device operates in hiccup
mode for protection. While in hiccup mode cycle, the device turns off RBFET for t_{OTG_OCP_OFF} (30 ms typical) and
turns on RBFET for t_{OTG_OCP_ON} (250 µs typical) in an attempt to restart. If the overcurrent condition is removed,
the boost converter returns to normal operation. When overcurrent condition continues to exist, the device
repeats the hiccup cycle until overcurrent condition is removed. When overcurrent condition is detected the fault
register bit BOOST_FAULT is set high to indicate fault in boost operation. An INT is also asserted to the host.
8.2.15.2.2 Boost Mode Overvoltage Protection
When the VBUS voltage rises above regulation target and exceeds V_{OTG_OVP}, the device enters overvoltage
protection which stops switching, clears OTG_CONFIG bit and exits boost mode. During the 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.
8.2.16 Battery Protection
8.2.16.1 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.
8.2.16.2 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.
8.2.16.3 System Overcurrent Protection
When the system is shorted or significantly overloaded (I_BAT > I_BATOP) so that its current exceeds the overcurrent
limit, the device latches off BATFET. Section BATFET Enable (Exit Shipping Mode) can reset the latch-off
condition and turn on BATFET
8.2.17 Serial Interface
The device uses I²C compatible interface for flexible charging parameter programming and instantaneous device
status reporting. I²C is a bi-directional 2-wire serial interface. Only two open-drain bus lines are required: a serial
data line (SDA) and a serial clock line (SCL). Devices can be considered as masters or slaves when performing
data transfers. A master is the device which initiates a data transfer on the bus and generates the clock signals
to permit that transfer. At that time, any device addressed is considered a slave.
The device operates as a slave device with address 6AH, receiving control inputs from the master device like
micro controller or a digital signal processor through REG00-REG14. Register read beyond REG14 (0x14)
returns 0xFF. The I²C interface supports both standard mode (up to 100 kbits), and fast mode (up to 400 kbits).
When the bus is free, both lines are HIGH. The SDA and SCL pins are open drain and must be connected to the
positive supply voltage via a current source or pull-up resistor.
30
Submit Documentation Feedback
Product Folder Links: BQ25890H
Copyright © 2016, Texas Instruments Incorporated