The TCA5405 from Texas Instruments is a single-wire I/O expander with STSW (self-timed, single-wire) technology. The expander can control and expand outputs to five, using a single processor GPIO. According to the company, this I/O expander reduces the number of connections needed, thus eliminating 50% of the lines versus I2C, and 75% compared to a SPI bus. The expander is suitable for mobile phones, PDAs , portable media players, and portable instrumentation devices such as blood glucose meters and insulin pumps. The company claims that an easy implementation of port expansion makes the expander suitable for simple functions, such as chip select or enable pins, as well as complex functions like driving LEDs of less than 20mA. The expander features standby current consumption and supports power-sensitive, high-performance applications with 2µA and a drive strength current of ±20mA, according to the company. The company offers free tools and support to speed development time such as the expander's IBIS (input output buffer information specification) model. The expander features an one-wire protocol-based port expansion in an 8pin, 2.25mm2 RUG micro-QFN package.
