NXP Semiconductors – PCAL6524 : Level-shifting I/O expander supports ultra-low voltage operation


The PCAL6524 is a 24-bit general purpose I/O expander which provides remote I/O expansion suitable for most microcontrollers, via a Fast-mode Plus (Fm+) I2C bus interface. Its ultra-low voltage interface allows for direct connection to an MCU operating at a voltage as low as 0.8V.

I/O expanders provide a simple solution when additional I/Os are needed while keeping interconnections to a minimum. This is useful, for example, in battery-powered mobile applications for interfacing an MCU to sensors, push buttons and a keypad.

In addition to providing a flexible set of GPIOs, the PCAL6524’s built-in level-shifting capability simplifies interconnection of a processor running at one voltage level to I/O devices operating at a different voltage level. The PCAL6524 operates from two supply voltages: one provides the supply voltage for the interface at the master side (for example, to an MCU), and the other provides the supply for core circuits.

The PCAL6524 conforms to the Fm+ I2C bus specification at speeds up to 1MHz, and implements Agile I/O features such as:
• programmable output-drive strength
• latchable inputs
• programmable pull-up/pull-down resistors
• maskable interrupt
• interrupt status register
• programmable open-drain or push-pull outputs

The device’s outputs can sink 25mA to directly drive LEDs.


  • 2μA stand-by current at 3.3V
  • Internal power-on reset
  • 5.5V-tolerant I/O ports and 3.6V-tolerant I2C bus pins
  • Noise filter on inputs
  • 2kV ESD protection according to the human body model


  • Companion device to a microcontroller


STMicroelectronics – TSU10x
STMicroelectronics – STM32L486xx