The MIC74 is a fully programmable serial-to-parallel I/O expander compatible with the SMBus™ (system management bus) protocol. It acts as a “slave” on the bus, providing eight independent I/O lines.

Each I/O bit can be individually programmed as an input or output. If programmed as an output, each I/O bit can be programmed as an open-drain or complementary push-pull output. If desired, the four most significant I/O bits can be programmed to implement fan speed control. An internal clock generator and state machine eliminate the overhead generally associated with “bit-banging” fan speed control.

Programming the device and reading/writing the I/O bits is accomplished using seven internal registers. All registers can be read by the host. Output bits are capable of directly driving high-current loads such as LEDs. A separate interrupt output can notify the host of state changes on the input bits without requiring the MIC74 to perform a transaction on the serial bus or be polled by the host. Three address selection inputs are provided, allowing up to eight devices to share the same bus and provide a total of 64 bits of I/O.

The MIC74 is available in an ultra-small-footprint 16-lead QSOP. Low quiescent current, small footprint, and low package height make the MIC74 ideal for portable and desktop applications.

• Provides eight bits of general purpose I/O
• Built in fan speed control logic (optional)
• 2-wire SMBus™/I2C™ compatible serial interface plus interrupt output
• 2.7V to 3.6V operating voltage range
• 5V-tolerant I/O
• Low quiescent current: 2µA (typical)
• Bit-programmable I/O options:
  • input or output
  • push-pull or open-drain output
  • interrupt on input changes
• Outputs can directly drive LEDs (10mA IOL)
• Up to 8 devices per bus

• General purpose I/O expansion via serial bus
• Personal computer system management
• Distributed sensing and control
• Microcontroller I/O expansion
• Fan Control