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1. General description
The PCA9552 LED blinker blinks LEDs in I
2
C-bus and SMBus applications where it is
necessary to limit bus traffic or free up the I
2
C-bus master's (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 I
2
C-bus and uses up one of the master's timers. The
PCA9552 LED blinker instead requires only the initial setup command to program
BLINK RATE 1 and BLINK RATE 2 (that is, the frequency and duty cycle) for each
individual output. 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 200 mA per package.
Any bits not used for controlling the LEDs can be used for General Purpose Parallel
Input/Output (GPIO) expansion.
The active LOW hardware reset pin (RESET) and Power-On Reset (POR) initializes the
registers to their default state, all zeroes, causing the bits to be set HIGH (LED off).
Three hardware address pins on the PCA9552 allow eight devices to operate on the same
bus.
2. Features
■ 16 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
■ I
2
C-bus interface logic compatible with SMBus
■ Internal power-on reset
■ Noise filter on SCL/SDA inputs
■ Active LOW reset input
■ 16 open-drain outputs directly drive LEDs to 25 mA
■ Edge rate control on outputs
■ 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
PCA9552
16-bit I
2
C-bus LED driver with programmable blink rates
Rev. 05 — 9 March 2006 Product data sheet
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