TCA9548A I2C multiplexer: specs and pinout
An I2C switch chip that fans one I2C bus out to eight separate channels, so identical-address devices can share one controller. This page covers the TCA9548A chip; the breakout board (pull-ups, address jumpers, header order) is not covered by an official document.
Specs
| Spec | Value | Source |
|---|---|---|
| Supply voltage VCC | 1.65 V to 5.5 V | source Recommended Operating Conditions, p.4 |
| Channels | 8 bidirectional translating switches, any combination selectable by a control register | source Features / Description, p.1 |
| I2C address | 0x70 to 0x77, set by A0, A1, A2 tied to VCC or ground | source Table 7-1 Address Reference (section 7.5.2) |
| Clock frequency | 0 to 400 kHz | source Features, p.1 |
| Input tolerance | 5 V tolerant inputs; SCL, SDA VIH 0.7 x VCC, up to 6 V | source Features p.1; Recommended Operating Conditions p.4 |
| Power-up state | All channels deselected at power-up; active-low RESET input deselects all channels | source Features / Description, p.1 |
| Supply current | 20 uA typ (35 uA max) at 3.6 V and 400 kHz; 0.1 uA typ standby (2 uA max) | source Electrical Characteristics, p.6 |
| Operating temperature | -40 C to 85 C (up to 125 C when VCC is 3.6 V or less) | source Recommended Operating Conditions, p.4 |
| Voltage translation | Allows level translation between 1.8 V, 2.5 V, 3.3 V and 5 V buses | source Features, p.1 |
Power
| Value | Source | |
|---|---|---|
| Supply | VCC 1.65-5.5 V | source Electrical Characteristics, p.6 |
| Current | 20 uA typ at 3.6 V, 400 kHz; 6 uA at 100 kHz (excluding bus pull-ups) | source Electrical Characteristics, p.6 |
Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.
The pins above are the bare TCA9548A. The module board is not covered by an official document. Whether the breakout fits its own pull-ups and which pads set the address is not verified.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| A0 / A1 / A2 | Address inputs | VCC or GND | 0x70-0x77 | source Table 4-1 p.3; Table 7-1 |
| RESET | Active-low reset input | connect to VCC or a pull-up if unused | source Table 4-1, p.3 | |
| SDA / SCL | Upstream serial data and clock | Connect to controller bus through pull-ups | source Table 4-1, p.3 | |
| SD0-SD7 | Downstream serial data, channels 0-7 | Each through a pull-up to its channel voltage | source Table 4-1, p.3 | |
| SC0-SC7 | Downstream serial clock, channels 0-7 | Each through a pull-up to its channel voltage | source Table 4-1, p.3 | |
| VCC | Supply voltage | 1.65-5.5 V | source Table 4-1, p.3 | |
| GND | Ground | source Table 4-1, p.3 |
Build with it
Project ideas for the TCA9548A I2C multiplexer. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Four identical OLED screens: Identical OLEDs share one I2C address; the multiplexer puts each on its own channel so only the selected one hears the bus. The ESP32 and the OLEDs run at 3.3 V, inside the chip's 1.65-5.5 V range.
- Multi-point climate logger: The multiplexer lets several boards with the same address coexist, one channel each; select a channel, read, then move to the next.
- Uno multi-sensor hub: Each channel's pull-ups go to the voltage the downstream board accepts; the stocked MPU6050 module's I2C level is not documented (the chip is a 3.3 V device), so confirm it before using the Uno's 5 V. The chip itself accepts up to 5.5 V on VCC. Check whether the boards already carry pull-ups. An ESP32 at 3.3 V avoids the question.
Common mistakes
- Leaving A0-A2 floating: the sheet says to connect them directly to VCC or ground; the address is 0x70 plus the A2:A1:A0 value (source)
- Forgetting pull-up resistors, or pulling a channel up to a voltage the sensor board does not accept: SDA, SCL and every SCn/SDn pair connect to their reference voltage through pull-ups, and the sheet lets each channel sit at a different voltage (1.8, 2.5, 3.3 or 5 V) from VCC, so pull each pair up to the voltage the downstream board takes, not automatically to VCC (source: link, Features and the translation section)
- Forgetting to select a channel: all channels are deselected at power-up, so nothing downstream responds until the control register is written; RESET must be tied high when not used (source)
Not covered by the official source
- Breakout board undocumented: pull-up values and address pad layout unknown.
Sources
- link (TI TCA9548A, SCPS207H, May 2012 revised Sept 2024; maker)