Low-Voltage 16-Bit I²C-Bus GPIO with Agile I/O, Interrupt and Weak Pull-up

PCAL9555A

The PCAL9555A is a low-voltage 16-bit General Purpose Input/Output (GPIO) expander with interrupt and weak pull-up resistors for I²C-bus/SMBus applications. NXP® I/O expanders provide a simple solution when additional I/Os are needed while keeping interconnections to a minimum, for example, in ACPI power switches, sensors, push buttons, LEDs, fan control, etc.

In addition to providing a flexible set of GPIOs, the wide VDD range of 1.65 V to 5.5 V allows the PCAL9555A to interface with next-generation microprocessors and microcontrollers where supply levels are dropping down to conserve power.

The PCAL9555A contains the PCA9555 register set of four pairs of 8-bit Configuration, Input, Output, and Polarity Inversion registers, and additionally, the PCAL9555A has Agile I/O, which are additional features specifically designed to enhance the I/O. These additional features are 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 PCAL9555A is a pin-to-pin replacement to the PCA9555, however, the PCAL9555A powers up with all I/O interrupts masked. This mask default allows for a board bring-up free of spurious interrupts at power-up.

The PCAL9555A open-drain interrupt (INT) output is activated when any input state differs from its corresponding Input Port register state and is used to indicate to the system leader that an input state has changed.

INT can be connected to the interrupt input of a microcontroller. By sending an interrupt signal on this line, the remote I/O can inform the microcontroller if there is incoming data on its ports without having to communicate via the I²C-bus. Thus, the PCAL9555A can remain a simple follower device.

The device outputs have 25 mA sink capabilities for directly driving LEDs while consuming low device current.

The power-on reset sets the registers to their default values and initializes the device state machine.

The device powers on with weak pull-up resistors enabled that can replace external components.

Three hardware pins (A0, A1, A2) select the fixed I²C-bus address and allow up to eight devices to share the same I²C-bus/SMBus.

Product Details

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Features

System Features

  • I²C-bus to parallel port expander
  • Operating power supply voltage range of 1.65 V to 5.5 V
  • Low standby current consumption
    • 1.5 μA (typical at 5 V VDD)
    • 1.0 μA (typical at 3.3 V VDD)
  • Schmitt-trigger action allows slow input transition and better switching noise immunity at the SCL and SDA inputs
    • Vhys = 0.10 x VDD (typical)
  • 5 V tolerant I/Os
  • Open-drain active LOW interrupt output (INT)
  • 400 kHz Fast-mode I²C-bus
  • Internal power-on reset
  • Power-up with all channels configured as inputs and weak pull-up resistors
  • No glitch on power-up
  • Latched outputs with 25 mA drive maximum capability for directly driving LEDs
  • Latch-up performance exceeds 100 mA per JESD78, Class II
  • ESD protection exceeds JESD22
    • 2000 V Human Body Model (A114-A)
    • 1000 V Charged-Device Model (C101)
  • Packages offered: TSSOP24, HVQFN24

Agile I/O Features

  • Pin to pin replacement for PCA9555 and PCA9555A with interrupts disabled at power-up
    • Software backward compatible with PCA9555 and PCA9555A
  • Output port configuration: bank selectable push-pull or open-drain output stages
  • Interrupt status: read-only register identifies the source of an interrupt
  • Bit-wise I/O programming features
    • Output drive strength: four programmable drive strengths to reduce rise and fall times in low capacitance applications
    • Input latch: Input Port register values changes are kept until the Input Port register is read
    • Pull-up/pull-down enable: floating input or pull-up/down resistor enable
    • Pull-up/pull-down selection: 100 kΩ pull-up/down resistor selection
    • Interrupt mask: mask prevents the generation of the interrupt when input changes state

Documentation

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Design Files

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  • Symbols and Footprints

    PCAL9555AHF-HWQFN24-CAD Symbol and PCB Footprint – BXL File

    ZIPRev 1Jul 9, 2020 13:32:0057.2 KBPCAL9555AHF-HWQFN24-BXL
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  • Design Files - miscellaneous

    Expert mode sample code for 16-bit Totem Pole

    TXTRev 1.0Dec 10, 2014 00:00:002.1 KB16-BIT-TOTEM-POLE-READ-WRITE
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