TCA9548A_15 Datasheet, PDF (12/35 Pages) Texas Instruments – Low-Voltage 8-Channel I2C Switch With Reset

TCA9548A
SCPS207E – MAY 2012 – REVISED OCTOBER 2015
www.ti.com
8.3 Feature Description
The TCA9548A is an 8-channel, bidirectional translating switch for I²C buses that supports Standard-Mode (100
kHz) and Fast-Mode (400 kHz) operation. The TCA9548A features I²C control using a single 8-bit control register
in which each bit controls the enabling and disabling of one of the corresponding 8 switch channels for I²C data
flow. Depending on the application, voltage translation of the I²C bus can also be achieved using the TCA9548A
to allow 1.8-V, 2.5-V, or 3.3-V parts to communicate with 5-V parts. Additionally, in the event that communication
on the I²C bus enters a fault state, the TCA9548A can be reset to resume normal operation using the RESET pin
feature or by a power-on reset which results from cycling power to the device.
8.4 Device Functional Modes
8.4.1 RESET Input
The RESET input is an active-low signal that may be used to recover from a bus-fault condition. When this signal
is asserted low for a minimum of t_WL, the TCA9548A resets its registers and I²C state machine and deselects all
channels. The RESET input must be connected to V_CC through a pull-up resistor.
8.4.2 Power-On Reset
When power is applied to the VCC pin, an internal power-on reset holds the TCA9548A in a reset condition until
V_CC has reached V_PORR. At this point, the reset condition is released, and the TCA9548A registers and I²C state
machine are initialized to their default states, all zeroes, causing all the channels to be deselected. Thereafter,
V_CC must be lowered below V _PORF to reset the device.
8.5 Programming
8.5.1 I²C Interface
The TCA9548A has a standard bidirectional I²C interface that is controlled by a master device in order to be
configured or read the status of this device. Each slave on the I²C bus has a specific device address to
differentiate between other slave devices that are on the same I²C bus. Many slave devices will require
configuration upon startup to set the behavior of the device. This is typically done when the master accesses
internal register maps of the slave, which have unique register addresses. A device can have one or multiple
registers where data is stored, written, or read.
The physical I²C interface consists of the serial clock (SCL) and serial data (SDA) lines. Both SDA and SCL lines
must be connected to V_CC through a pull-up resistor. The size of the pull-up resistor is determined by the amount
of capacitance on the I²C lines. (For further details, refer to I²C Pull-up Resistor Calculation (SLVA689).) Data
transfer may be initiated only when the bus is idle. A bus is considered idle if both SDA and SCL lines are high
after a STOP condition.
The following is the general procedure for a master to access a slave device:
1. If a master wants to send data to a slave:
– Master-transmitter sends a START condition and addresses the slave-receiver.
– Master-transmitter sends data to slave-receiver.
– Master-transmitter terminates the transfer with a STOP condition.
2. If a master wants to receive or read data from a slave:
– Master-receiver sends a START condition and addresses the slave-transmitter.
– Master-receiver sends the requested register to read to slave-transmitter.
– Master-receiver receives data from the slave-transmitter.
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