PCAL9535AHF,128

I/o Expanders Overview

The PCAL9535AHF,128 is a low-voltage 16-bit General Purpose Input/Output (GPIO) expander designed for I2C-bus and SMBus applications. It features Agile I/O capabilities including programmable output drive strength, latchable inputs, and configurable pull-up/pull-down resistors. The device operates within a supply voltage range of 1.65 V to 5.5 V and supports Fast-mode communication at up to 400 kHz. Packaged in a 24-terminal HWQFN24 plastic thermal enhanced very thin quad flat package, it provides an open-drain interrupt output and includes internal power-on reset functionality.

I/o Expanders Feature Summary

• Agile I/O features enable bit-wise programming of output drive strength, input latching, and pull-up/pull-down resistor selection.
• Open-drain active LOW interrupt output signals system masters when input states change without requiring continuous bus polling.
• Hardware address pins allow up to eight devices to share the same I2C-bus/SMBus interface simultaneously.

I/o Expanders Applications

• ACPI power switches
• Sensor interfaces
• Push button arrays
• LED driving circuits
• Fan control systems

I/o Expanders Procurement Notes

Verify the specific ordering suffix ',128' corresponds to the HWQFN24 reel pack configuration with a minimum order quantity of 6000 units. Confirm that the component meets RoHS compliance standards and matches the specified temperature range of -40 °C to +85 °C before finalizing procurement orders.

I/o Expanders Selection Notes

Select this component when software backward compatibility with PCA9535 or PCA9535A is required alongside enhanced Agile I/O features. Ensure the design accommodates the 24-HWQFN package dimensions and utilizes the exposed center pad for proper thermal dissipation and electrical grounding during PCB layout.

I/o Expanders Part Context

This part belongs to the PCAL9535A series, which serves as a pin-to-pin replacement for the PCA9535 and PCA9535A families. Unlike its predecessors, the PCAL9535A powers up with all I/O interrupts masked by default, preventing spurious interrupts during board bring-up while maintaining full register compatibility.

I/o Expanders Replacement Considerations

PCAL9535AHF,128 is a direct pin-to-pin replacement for PCA9535AHF,128 and PCA9535APW,118 variants. Designers should note that the PCAL9535A initializes with interrupts disabled, whereas older models may behave differently upon power-up.

I/o Expanders FAQ

How does the PCAL9535A handle interrupts at power-up?

The PCAL9535A powers up with all I/O interrupts masked by default. This prevents spurious interrupts during system start-up, ensuring a clean board bring-up process compared to previous generations.

What is the function of the Agile I/O feature?

Agile I/O provides additional programmable features such as selectable output drive strength, latchable inputs, and configurable internal pull-up/pull-down resistors, enhancing flexibility beyond standard GPIO expansion.

Can the PCAL9535A be used as a drop-in replacement for the PCA9535?

Yes, the PCAL9535A is a pin-to-pin replacement for the PCA9535 and PCA9535A. It is software backward compatible but introduces the default masking of interrupts at power-on.