TCA9546A Datasheet, PDF (16/31 Pages) Texas Instruments – Low Voltage 4-Channel I2C and SMBus Switch with Reset Function

TCA9546A
SCPS205A – APRIL 2014 – REVISED FEBRUARY 2015
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10 Application and Implementation
10.1 Application Information
Applications of the TCA9546A will contain an I²C (or SMBus) master device and up to four I²C slave devices.
The downstream channels are ideally used to resolve I²C slave address conflicts. For example, if four identical
digital temperature sensors are needed in the application, one sensor can be connected at each channel: 0, 1, 2,
and 3. When the temperature at a specific location needs to be read, the appropriate channel can be enabled
and all other channels switched off, the data can be retrieved, and the I²C master can move on and read the next
channel.
In an application where the I²C bus will contain many additional slave devices that do not result in I²C slave
address conflicts, these slave devices can be connected to any desired channel to distribute the total bus
capacitance across multiple channels. If multiple switches will be enabled simultaneously, additional design
requirements must be considered (See Design Requirements and Detailed Design Procedure).
10.2 Typical Application
A typical application of the TCA9546A will contain anywhere from 1 to 5 separate data pull-up voltages, V_DPUX ,
one for the master device (V_DPUM) and one for each of the selectable slave channels (V_DPU0 – V_DPU3). In the
event where the master device and all slave devices operate at the same voltage, then the pass voltage, V_pass =
V_DPUX. Once the maximum V_pass is known, V_cc can be selected easily using Figure 16. In an application where
voltage translation is necessary, additional design requirements must be considered (See Design Requirements).
Figure 15 shows an application in which the TCA9546A can be used.
V_DPUM = 1.65 V to 5.5 V
SDA
I²C/SMBus _SCL
Master
V_CC = 3.3 V
16
VCC
15
SDA
4
SD0
14 _SCL
5
SC0
3
RESET
V_DPU0 = 1.65 V to 5.5 V
Channel 0
V_DPU1 = 1.65 V to 5.5 V
SD1 ⁶
SC1 ⁷
TCA9546A
Channel 1
V_DPU2 = 1.65 V to 5.5 V
13
A2
2
A1
1 _A0
8
GND
9
SD2
SC2 ¹⁰
11
SD3
SC3 ¹²
Channel 2
V_DPU3 = 1.65 V to 5.5 V
Channel 3
Figure 15. TCA9546A Typical Application Schematic
16
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