Interface IC (FCA Series)

FCA Series Interface ICs Overview

Interface ICs are integrated circuits used to establish electrical connections and data paths between a host controller and peripheral devices. Depending on the interface standard and system requirements, these ICs may perform functions such as data transmission and reception, signal buffering, protocol bridging, bus switching, logic-level adaptation, and port expansion. These functions enable devices to exchange information under specified electrical conditions and communication timing requirements. Because the functions of interface ICs vary significantly by device type, product selection should be based on the target bus, signal direction, communication speed, and system interconnection architecture.

The FCA Series includes the FCA8574, FCA9535, FCA9539, FCA9555, FCA9548, and other interface ICs, covering I²C I/O expanders and I²C/SMBus bus switches. These devices can be used to expand processor GPIO resources, manage multiple downstream I²C buses, resolve slave-address conflicts, and interconnect segmented I²C buses operating at different supply voltages.

The FCA8574 provides an 8-bit quasi-bidirectional I/O port without a dedicated direction-control register. Output states are controlled by writing data to the port, while input states are obtained by reading the port. The FCA9535, FCA9539, and FCA9555 provide 16-bit GPIO ports, with each I/O pin independently configurable as an input or output through registers. Depending on the model, these devices support hardware address selection, input-state reading, output latching, and an active-low, open-drain interrupt output. The FCA9539 also provides an active-low hardware reset input.

The FCA9548 is an 8-channel bidirectional I²C/SMBus switch that allows one or more downstream channels to be selected through a control register. It connects one upstream pair of SDA and SCL lines to eight downstream buses and is suitable for systems containing multiple I²C slave devices with identical addresses, requiring bus segmentation, or requiring the isolation of faulty channels. When separate pull-up supplies are used for individual channels, the device can interconnect I²C buses operating at different logic voltages under the conditions specified in the datasheet. The FCA9548 also provides an active-low reset input that resets the I²C state machine and deselects all downstream channels.

The FW28E17Q is an interface IC but is not part of the FCA Series. It is a 1-Wire slave-to-I²C master communication bridge that converts data received over a 1-Wire bus into I²C master transactions. It can be used to control remote I²C sensors, display controllers, analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and other I²C slave devices. The device includes a factory-programmed, unique 64-bit 1-Wire ROM ID, supports sleep and wake-up functions, and provides busy-status and communication-error indications. It is suitable for systems with limited GPIO resources or applications requiring remote I²C peripherals to be connected through a 1-Wire bus.

FCA Series and FW interface ICs can be used in servers, routers, communications equipment, industrial automation systems, remote sensor nodes, and other electronic products with limited interface resources. Device selection should take into account the interface type, number of GPIOs, port architecture, number of bus channels, device address, supply voltage, communication speed, operating temperature range, and package dimensions.

I²C, SMBus, and 1-Wire buses, as well as open-drain interrupt signals, typically require external pull-up resistors selected according to bus capacitance, communication speed, and supply voltage. Detailed connection requirements and electrical limitations are provided in the official datasheet for each device.