I/O Expansion Chip Empowers MCU-Based Systems

Expanding microcontroller-based system capabilities, the MC33993 I/O expansion device adds switch monitoring, LED and FET drivers, and programmable wake-up to low-pin-count microcontrollers (MCUs). The chip interfaces with a MCU through a four-pin serial peripheral interface (SPI), increasing the number of I/O signals to up to five or more. It includes an analog multiplex feature that allows up to 22 analog signals to be sent to one MCU A/D input. The chip's 22 I/O pins can be configured to detect switch contact status (open/closed), provide an analog value to a buffered output, drive aLED or FET, and/or to provide switched power to a low-current sensor. Other features include 3.3V and 5V I/O MCU interfaces, contact wetting that provides up to 16 mA of output current to each of the switch input pins, daisy-chaining via the SPI, ESD protection up to 25 kV, and a wakeup timer. Housed in a 32-lead SOIC, pricing starts at $1.50 each/10,000. An evaluation board, part number KIT33993DHEVB, is available for $99. MOTOROLA INC., Austin, TX. (512) 895-2000.