General description
The NCA9539 provides 16 bits of General Purpose Input/Output (GPIO) expansion with interrupt
and reset for I²C-bus/SMBus applications. It is designed for a wide voltage range of 1.65 V to
5.5 V. 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 NCA9539 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 read register. The NCA9539 has an opendrain
interrupt output which is activated when any one of the GPIO changes from its corresponding
input port register state. 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, NCA9539 can
remain a simple slave. The power on reset sets the registers to default values and initializes the
device state machine. The RESET pin can be used to achieve same reset functionality without
power down/up cycling by keeping active low. The state machine and the registers are in their
default state until the RESET input is once again HIGH. This input requires pull up to VCC. The
NCA9539 has two address pins A0 and A1 which can be used to configure the I²C bus slave
address of the device. It allows up-to four 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
• Open-drain active LOW interrupt output (INT)
• Reset input for resetting NCA9539 to default values (RESET)
• 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