PCA9550

    The PCA9550 LED Blinker blinks LEDs in I² C-bus and SMBus applications where it is necessary to limit bus traffic or free up theI²C Master!s (MCU, MPU, DSP, chipset, etc.) timer. The uniquenes of PCA9550 is the internal oscillator with two programmable blink rates. To blink LEDs using normal I/O Expanders like the PCF8574 or PCA9554, the bus master must send repeated commands to turn the LED on and off. This greatly increases the amount of traffic onthe I²C-bus and uses up one of the master!s timers.

    The PCA955 LED Blinker instead requires only the initial set up command to program BLINK RATE 1 and BLINK RATE 2 (i.e., the frequency and duty cycle). From then on, only one command from the bus master is required to turn each individual open drain output ON, OFF, or to cycle at BLINK RATE 1 or BLINK RATE 2. Maximum output sink current is 25 mA per bit and 50 mA per package.