TCA9546A Datasheet, PDF (10/31 Pages) Texas Instruments – Low Voltage 4-Channel I2C and SMBus Switch with Reset Function

TCA9546A
SCPS205A – APRIL 2014 – REVISED FEBRUARY 2015
9 Detailed Description
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9.1 Overview
The TCA9546A is a 4-channel, bidirectional translating I²C switch. The master SCL/SDA signal pair is directed to
four channels of slave devices, SC0/SD0-SC3/SD3. Any individual downstream channel can be selected as well
as any combination of the four channels.
The device offers an active-low RESET input which resets the state machine and allows the TCA9546A to
recover should one of the downstream I²C buses get stuck in a low state. The state machine of the device can
also be reset by cycling the power supply, V_CC, also known as a power-on reset (POR). Both the RESET function
and a POR will cause all channels to be deselected.
The connections of the I²C data path are controlled by the same I²C master device that is switched to
communicate with multiple I²C slaves. After the successful acknowledgment of the slave address (hardware
selectable by A0 and A1 pins), a single 8-bit control register is written to or read from to determine the selected
channels.
The TCA9546A may also be used for voltage translation, allowing the use of different bus voltages on each
SCn/SDn pair such that 1.8-V, 2.5-V, or 3.3-V parts can communicate with 5-V parts. This is achieved by using
external pull-up resistors to pull the bus up to the desired voltage for the master and each slave channel.
9.2 Functional Block Diagram
TCA9546A
SC0 ⁵
SC1 ⁷
SC2 ¹⁰
SC3 ¹²
SD0 ⁴
SD1 ⁶
SD2 ⁹
SD3 ¹¹
GND ⁸
VCC ¹⁶
RESET ³
SCL ¹⁴
SDA ¹⁵
Power-On Reset
Input Filter
Switch Control Logic
I²C Bus Control
1 _A0
2 _A1
13 _A2
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