TCA9847 1MHz 8-Channel I2C Multiplexer

Introduction

Texas Instruments’ TCA9847 is a 1-to-8 bidirectional I²C/SMBus multiplexer with integrated voltage-level translation. It connects a single upstream SCL/SDA interface to as many as eight individually selectable downstream channel pairs, supporting bus clock frequencies from 0 to 1 MHz.

The device is intended for systems where multiple I²C or SMBus segments must share one upstream controller connection. Its channel-selection capability can also resolve target-address conflicts between downstream devices, allowing otherwise conflicting targets to be accessed on separate channels.

What it does

The TCA9847 provides one upstream SCL/SDA pair and eight downstream SCn/SDn pairs. Each downstream channel can be selected independently, enabling an upstream I²C or SMBus bus to communicate with devices placed on different branches.

Bidirectional voltage translation supports mixed-voltage bus connections. VDD1 operates from 0.65 V to 3.6 V, while VDD2 operates from 1.65 V to 3.6 V, with supported translation levels including 0.65 V, 0.8 V, 1.2 V, 1.8 V, 2.5 V, and 3.3 V. The I/O interfaces are 3.6 V tolerant.

Two address pins support up to 16 devices on an I²C bus. An active-low reset input initializes the I²C/SMBus state machine and deselects all channels, providing a defined starting state after reset.

Applications

• I²C or SMBus systems requiring connection to multiple downstream bus segments
• Designs using multiple I²C targets with overlapping addresses
• Mixed-voltage control buses requiring bidirectional level translation
• Systems that need to isolate or selectively access one of several I²C peripheral groups
• Multi-device boards using additional multiplexers on the same I²C bus

Design considerations

The TCA9847 supports I²C and SMBus operation up to 1 MHz, so the selected bus speed should remain within that range. System designers should account for the separate VDD1 and VDD2 supply ranges when interfacing buses operating at different logic-voltage levels.

Each downstream branch uses its own SCL and SDA pair, and channels are individually selectable rather than permanently connected to the upstream bus. The active-low reset input deselects all channels, which should be considered in startup and fault-recovery behavior. The two address pins also provide a path to using multiple TCA9847 devices where more than eight downstream channels are required.

Availability and further information

The source/distributor and datasheet links on this page provide further information on the TCA9847, including complete electrical characteristics, operating details, and integration guidance.