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PCAL9538A: Low-voltage 8-bit I²C-bus and SMBus low power I/O port with interrupt, reset and Agile I/O

The PCAL9538A is a low-voltage 8-bit General Purpose Input/Output (GPIO) expander with interrupt and reset 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 PCAL9538A to interface with next-generation microprocessors and microcontrollers where supply levels are dropping down to conserve power.

The PCAL9538A contains the PCA9538A register set of four 8-bit Configuration, Input, Output, and Polarity Inversion registers, and additionally, the PCAL9538A 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 PCAL9538A is a pin-to-pin replacement for the PCA9538, however, the PCAL9538A 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 PCAL9538A 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 master 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 PCAL9538A can remain a simple slave 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. In the PCAL9538A, the RESET pin causes the same reset/default I/O input configuration to occur without de-powering the device, holding the registers and I²C-bus state machine in their default state until the RESET input is once again HIGH. This input requires a pull-up to VDD.

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

Outline 3d SOT403-1

• Pin to pin replacement for PCA9538 and PCA9538A with interrupts disabled at power-up Software backward compatible with PCA9538 and PCA9538A
• 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

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Package Information (2)

Packing (1)

Supporting Information (1)

Ordering Information

Package Information

Product ID	Package Description	Outline Version	Reflow/Wave Soldering	Packing	Product Status	Part NumberOrdering code(12NC)	Marking	Chemical Content	RoHS / Pb Free / RHF	LeadFree Conversion Date	MSL	MSL LF
PCAL9538ABS		SOT758-1		Reel 13" Q2/T3	Active	PCAL9538ABSHP (9352 993 91128)	L3A	PCAL9538ABS		Always Pb-free	1	1
PCAL9538APW		SOT403-1	SSOP-TSSOP-VSO-WAVE	Reel 13" Q1/T1	Active	PCAL9538APWJ (9352 993 89118)	PL9538A	PCAL9538APW		Always Pb-free	1	1