TXE8148 48-Bit SPI Bus I/O Expander

Introduction

Texas Instruments’ TXE8148 is a 48-bit general-purpose I/O expander designed to add substantial parallel GPIO capacity through a four-wire SPI connection. Its six eight-bit ports provide a compact interface between a host controller and external digital signals, while support for SPI daisy-chaining allows multiple expanders to be connected in systems where chip-select routing is limited.

Operating across a 1.65 V to 5.5 V supply range and supporting SPI bus frequencies up to 10 MHz, the device is suited to designs that need configurable GPIO without consuming a large number of native processor pins.

What it does

The TXE8148 converts serial SPI transactions into control and monitoring of 48 individually configurable I/O channels. Each I/O can be set for input or output operation, with per-pin selection of open-drain or push-pull output behavior.

Additional per-I/O configuration includes programmable pull-up or pull-down resistors, bus hold, polarity inversion, and glitch-filter selection. These functions allow a single expander to accommodate a mix of digital inputs and outputs with differing electrical requirements.

The device supports read and write transfers with burst mode, enabling access to multiple I/Os or registers in a single SPI operation. Its open-drain, active-low /INT output can signal the host when interrupt functionality is used, while an active-low /RESET input provides an external reset path. A fail-safe I/O mode is also provided.

Applications

• Expanding GPIO capacity on SPI-equipped microcontrollers and processors
• Monitoring groups of switches, status signals, or other digital inputs
• Driving control signals that require individually selectable push-pull or open-drain outputs
• Adding configurable I/O banks to embedded control boards
• Building systems with multiple GPIO expanders connected through an SPI daisy chain
• Interfacing host controllers to mixed-voltage digital logic within the 1.65 V to 5.5 V operating range

Design considerations

The TXE8148 provides 48 I/Os as six ports of eight, which may simplify allocation of signals by functional group. Designers can use the four-wire SPI interface in point-to-point arrangements or use the supported daisy-chain capability when connecting multiple devices.

Output behavior should be selected per I/O according to the connected circuitry: the device supports both open-drain and push-pull configurations and provides up to 10 mA output drive capability. Programmable pull-up and pull-down resistors, bus hold, and polarity inversion can reduce external support circuitry for compatible signals, while the selectable glitch filter may be useful for inputs requiring transient rejection.

The interrupt output is open-drain and active low, so the /INT line requires an appropriate pull-up arrangement. Likewise, integration of the active-low /RESET input should account for the required reset behavior of the wider system. Typical standby current is specified as 6 µA.

Availability and further information

Further technical information is available through the source/distributor and datasheet links provided on this page.