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Part Number Description Standby Current Max Output device current Default POR Output State Hardware Reset input Configuration Registers I/O Pull-Up Number of Device Address Cross Reference Max frequency (kHz) I2C Adress Vcc Range(V) Interrupt 5V-to lerant I/O Output type max I/O voltage tolerance Number of I/Os Pin/Package
AT9554A 0.25μA 10mA Hi-Z Input 100kΩ 8 PCA9554A 400 0111xxx 2.3~5.5 Totem-Pole 5.5V 8 TSSOP16 QFN16 SOP16(W)


     The AT9554 and AT9554A are 16-pin CMOS devices that provide 8 bits of General Purpose parallel Input/Output (GPIO) expansion for I2C-bus/SMBus applications.The improvements include higher drive capability, 5 V I/O tolerance, lower supply current,individual I/O configuration, 400 kHz clock frequency, and smaller packaging. I/O expanders provide a simple solution when additional I/O is needed for ACPI power switches, sensors, push buttons, LEDs, fans, and so on.

       The AT9554/AT9554A consist of an 8-bit Configuration register (Input or Output selection); 8-bit Input Port register, 8-bit Output Port register and an 8-bit Polarity Inversion register (active HIGH or active LOW operation). The system master can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. The data for each input or output is kept in the corresponding Input Port or Output Port register. The polarity of the read register can be inverted with the Polarity Inversion register. All registers can be read by the system master. Although pin-to-pin and I2C-bus address compatible with the AT8574 series, software changes are required due to the enhancements.

       The AT9554/AT9554A open-drain interrupt 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. The power-on reset sets the registers to their default values and initializes the device state machine.

       Three hardware pins (A0, A1, A2) vary the fixed I2C-bus address and allow up to eight devices to share the same I2C-bus/SMBus. The AT9554A is identical to the AT9554except that the fixed I2C-bus address is different allowing up to sixteen of these devices(eight of each) on the same I2C-bus/SMBus.


Operating power supply voltage range of2.3V to 5.5 V

5 V tolerant I/Os

Polarity Inversion register

Active LOW interrupt output

Low standby current

Noise filter on SCL/SDA inputs

No glitch on power-up

Internal power-on reset

8 I/O pins which default to 8 inputs

0 Hz to 400 kHz clock frequency

ESD protection exceeds 2000 V HBM per JESD22-A114 and 1000 V CDM perJESD22-C101

Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

AEC-Q100 compliance available

Packages offered: SO16, SSOP16, SSOP20, TSSOP16, HVQFN16 (2 versions:4x4x 0.85 mm and 3x 3 x 0.85 mm), and bare die

Typical Application


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