General description
The PCA9553 LED blinker blinks LEDs in I2C-bus and SMBus applications where it is necessary to limit bus traffic or free up the I2C-bus masters (MCU, MPU, DSP, chip set, etc.) timer. The uniqueness of this device 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 on the I2C-bus and uses up one of the masters timers. The PCA9553 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 100 mA per package.

FEATUREs
■ 4 LED drivers (on, off, flashing at a programmable rate)
■ 2 selectable, fully programmable blink rates (frequency and duty cycle) between
   0.172 Hz and 44 Hz (5.82 seconds and 0.023 seconds)
■ Input/outputs not used as LED drivers can be used as regular GPIOs
■ Internal oscillator requires no external components
■ I2C-bus interface logic compatible with SMBus
■ Internal power-on reset
■ Noise filter on SCL/SDA inputs
■ 4 open-drain outputs directly drive LEDs to 25 mA
■ Controlled edge rates to minimize ground bounce
■ No glitch on power-up
■ Supports hot insertion
■ Low standby current
■ Operating power supply voltage range of 2.3 V to 5.5 V
■ 0 Hz to 400 kHz clock frequency
■ ESD protection exceeds 2000 V HBM per JESD22-A114, 150 V MM per
   JESD22-A115 and 1000 V CDM per JESD22-C101
■ Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA
■ Packages offered: SO8, TSSOP8 (MSOP8), HVSON8