Texas Instruments (TI) has supported the highly efficient I²C BUS® interface with high performance microchips for many years. This overview provides an updated look at I²C applications and how TI’s I/O expanders, multiplexers, buffers and repeaters can help system designers achieve effective subsystem communications and interfacing using proven I²C devices.
TI's new TCA family of low voltage I²C peripherals provide a single chip solution for I²C interface with next-generation low-voltage processors. The wide operating voltage range supports legacy processors and peripherals along the I²C bus. TCA devices include the TCA6408 (sample) 8-bit I/O expander for the two-line bidirectional bus (I²C) is designed to provide general-purpose remote I/O expansion and the TCA6507 (sample), 7-bit LED dimmer for the two-line bidirectional bus (I²C) is designed to control (or dim) LEDs via the I²C interface [serial clock (SCL), serial data (SDA)]. The TCA family's low-voltage range, low power consumption, and small footprint make these I²C peripherals ideal for portable and consumer applications.
The PCA9557 (sample) is a 8-bit I/O expander for the two-line bidirectional bus (I²C) and is designed for 2.3-V to 5.5-V VCC operation. The device provides general-purpose remote I/O expansion for most microcontroller families via the I²C interface [serial clock (SCL) and serial data (SDA)]. The PCA9557 consists of one 8-bit configuration (input or output selection), input port, output port, and polarity inversion (active-high) registers. At power on, the I/Os are configured as inputs. However, the system master can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. The data for each input or output is kept in the corresponding input or output register. The polarity of the input port register can be inverted with the polarity inversion register. All registers can be read by the system master.
The PCF8574 (sample) and PCF8574A (sample) provide an interface to most microcontroller families via the I²C bus for general purpose remote I/O expansion. With these devices, the SCL line is unidirectional, from the microprocessor to the device. The PCF8574 and PCF8574A are functionally the same, but differ in their I²C addresses. By using the PCF8574 or PCF8574A or both, circuit designers can greatly simplify complex glue-logic interface circuit, increase I/O pin-count, reduce PCB area used, and improve system reliability.
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