BQ24298_15 Datasheet, PDF (27/51 Pages) Texas Instruments – bq24298 I2C Controlled 3A Single Cell USB Charger With Narrow VDC Power Path Management and Adjustable Voltage USB OTG

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bq24298
SLUSC59 – APRIL 2015
8.5 Programming
8.5.1 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).
Both SDA and SCL are bi-directional lines, connecting to the positive supply voltage via a current source or pull-
up resistor. When the bus is free, both lines are HIGH. The SDA and SCL pins are open drain.
8.5.1.1 Data Validity
The data on the SDA line must be stable during the HIGH period of the clock. The HIGH or LOW state of the
data line can only change when the clock signal on the SCL line is LOW. One clock pulse is generated for each
data bit transferred.
SDA
SCL
Data line stable;
Data valid
Change
of data
allowed
Figure 19. Bit Transfer on the I²C Bus
8.5.1.2 START and STOP Conditions
All transactions begin with a START (S) and can be terminated by a STOP (P). A HIGH to LOW transition on the
SDA line while SCl is HIGH defines a START condition. A LOW to HIGH transition on the SDA line when the
SCL is HIGH defines a STOP condition.
START and STOP conditions are always generated by the master. The bus is considered busy after the START
condition, and free after the STOP condition.
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