I²C bus now runs at 1MHz

Chip designers use the twowire, serial I²C bus for a range of interchip communications. Philips, which originated the bus more than 20 years ago, has now announced Fm+ (fast-modeplus) devices that take the performance of the I²C bus up to 1MHz. Previous increments in the speed of the bus include the 400kHz standard and fast modes. Devices that exploit the performance that Fm+ offers include LED controllers and chips dedicated to stand-alone-busdriving functions.

The four-color PCA9633 LED driver and controller for color-mixing applications features four controllers for the LED outputs and a fifth to simultaneously dim or blink all the LEDs. The chip has 4- bit level control and responds to four addresses, increasing the flexibility that programmers can use when creating lighting effects. Users can operate as many as 126 devices on the same bus without bus extenders.

Two other devices perform 40-bit I/O expansion. With the PCA9698, you can support as many as 64 nodes on the same bus. Features include 40 I/O pins with configurable outputs; output states that you can switch using acknowledge or stop commands; noninterrupt-generating , maskable interrupts; and an SMBusAlert function. The parallel-to-I2C PCA9665 controller drives buses having as much as 4-nF capacitance. You can use a standard microcontroller as an Fm+ bus master, and the device includes a 68-byte buffer to simplify programming.

-Graham Prophet EDN Europe Philips, www.philips.com