BQ25890_16 Datasheet, PDF (36/69 Pages) Texas Instruments – Adjustable Voltage USB On-the-Go Boost Mode

bq25890, bq25892
SLUSC86B – MARCH 2015 – REVISED MAY 2016
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Figure 24. Multi-Read
REG0C is a fault register. It keeps all the fault information from last read until the host issues a new read. For
example, if Charge Safety Timer Expiration fault occurs but recovers later, the fault register REG0C reports the
fault when it is read the first time, but returns to normal when it is read the second time. In order to get the fault
information at present, the host has to read REG0C for the second time. The only exception is NTC_FAULT
which always reports the actual condition on the TS pin. In addition, REG0C does not support multi-read and
multi-write.
9.3 Device Functional Modes
9.3.1 Host Mode and Default Mode
The device is a host controlled charger, but it can operate in default mode without host management. In default
mode, the device can be used an autonomous charger with no host or while host is in sleep mode. When the
charger is in default mode, WATCHDOG_FAULT bit is HIGH. When the charger is in host mode,
WATCHDOG_FAULT bit is LOW.
After power-on-reset, the device starts in default mode with watchdog timer expired, or default mode. All the
registers are in the default settings.
In default mode, the device keeps charging the battery with 12-hour fast charging safety timer. At the end of the
12-hour, the charging is stopped and the buck converter continues to operate to supply system load. Any write
command to device transitions the charger from default mode to host mode. All the device parameters can be
programmed by the host. To keep the device in host mode, the host has to reset the watchdog timer by writing 1
to WD_RST bit before the watchdog timer expires (WATCHDOG_FAULT bit is set), or disable watchdog timer by
setting WATCHDOG bits=00.
When the watchdog timer (WATCHDOG_FAULT bit = 1) is expired, the device returns to default mode and all
registers are reset to default values except IINLIM, VINDPM, VINDPM_OS, BATFET_RST_EN, BATFET_DLY,
and BATFET_DIS bits.
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