BQ24296_15 Datasheet, PDF (29/55 Pages) Texas Instruments – bq2429x I2C Controlled 3-A Single Cell USB Charger With Narrow VDC Power Path Management and Adjustable Voltage USB OTG

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bq24296, bq24297
SLUSBP6B – SEPTEMBER 2013 – REVISED NOVEMBER 2014
Device Functional Modes (continued)
When the host changes watchdog timer configuration (REG05[5:4]), it is recommended to first disable watchdog
by writing 00 to REG05[5:4] and then change the watchdog to new timer values. This ensures the watchdog
timer is restarted after new value is written.
POR
watchdog timer expired
Reset registers
I2C interface enabled
Y
I2C Write?
N
Default Mode
Reset watchdog timer
Reset registers
Host Mode
Start watchdog timer
Host programs registers
Reset REG01
Y
bit[6]?
N
Y
N
I2C Write?
Y
Watchdog Timer
N
Expired?
Figure 20. Watchdog Timer Flow Chart
9.4.1.1 Plug in USB100mA Source with Good Battery
When the input source is detected as 100mA USB host, and the battery voltage is above batgood threshold
(V_BATGD), the charger device enters HIZ state to meet the battery charging spec requirement.
If the charger device is in host mode, it will stay in HIZ state even after the USB100mA source is removed, and
the adapter plugs in. During the HIZ state, REG00[7] is set HIGH and the system load is supplied from battery. It
is recommended that the processor host always checks if the charger IC is in HIZ state when it wakes up. The
host can write REG00[7] to 0 to exit HIZ state.
If the charger is in default mode, when the DC source is removed, the charger device will get out of HIZ state
automatically. When the input source plugs in again, the charger IC runs detection on the input source and
update the input current limit.
9.4.1.2 USB Timer When Charging from USB100mA Source
The total charging time in default mode from USB100mA source is limited by a 45-min max timer. At the end of
the timer, the device stops the converter and goes to HIZ.
9.5 Programming
9.5.1 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 developed by Philips Semiconductor (now NXP
Semiconductors). Only two 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 6BH, receiving control inputs from the master device like
micro controller or a digital signal processor. The I²C interface supports both standard mode (up to 100 kbits),
and fast mode (up to 400 kbits).
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