General description
The NCA9555 provides 16 bits of General Purpose Input/Output (GPIO) expansion for
I²C-bus/SMBus applications. It is designed for a wide voltage range of 1.65 V to 5.5 V with interrupt
and default pull-up resistors on GPIOs. Nexperia GPIO expanders provide an elegant solution
when additional IOs are needed while keeping the interconnections to a minimum, for example,
in ACPI power switches, sensors, push buttons, LEDs and fan control. The NCA9555 contains a
set of 8 bit input, output, configuration and polarity inversion registers. At power up all IOs default
to inputs. Each IO can be configured as either input or output by changing the corresponding bit
in the configuration register. The data for each input or output is stored in the corresponding input
or output register. The polarity inversion register can be programmed to invert the polarity of the
input register. The NCA9555 has an open-drain interrupt output which is activated when any one
of the GPIO changes from its corresponding input port register state. The power on reset sets
the registers to default values and initializes the device state machine. The NCA9555 has three
address pins A0, A1 and A2 which can be used to configure the I²C bus slave address of the
device. It allows up-to eight devices to share the same I²C-bus/SMBus.

Features and benefits
• I²C-bus to parallel port expander
• Operating power supply voltage range of 1.65 V to 5.5 V
• Low standby current consumption:
• 2.5 μA (maximum)
• Schmitt-trigger action allows slow input transition and better switching noise immunity at the
SCL and SDA inputs
• Vhys = 0.10 × VCC (typical)
• Noise filter on SCL and SDA inputs
• 5 V tolerant I/Os
• 16 I/O pins which power up configured in input state with weak pull-up resistor
• Open-drain active LOW interrupt output (INT)
• 400 kHz Fast-mode I²C-bus
• Internal power-on reset
• 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:
• HBM ANSI/ESDA/JEDEC JS-001 Class 2 exceeds 2000 V
• CDM ANSI/ESDA/JEDEC JS-002 Class C3 exceeds 1000 V
• Specified from -40 °C to +85 °C