PCA9551 2 8-bit I C-bus LED driver with programmable blink rates Rev. 08 31 July 2008 Product data sheet 1. General description 2 The PCA9551 LED blinker blinks LEDs in I C-bus and SMBus applications where it is 2 necessary to limit bus trafc or free up the I 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 2 increases the amount of trafc on the I C-bus and uses up one of the master s timers. The PCA9551 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) 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 100 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 PCA9551 allow eight devices to operate on the same bus. The newer Fast-mode Plus PCA9634 8-bit LED controller offers an individual PWM dimming control for each channel for better color mixing capabilities with a global PWM for dimming or blinking all channels at the same time. There are 126 possible address combinations and the maximum output sink current is 25 mA per bit and 200 mA per package. 2. Features n 8 LED drivers (on, off, ashing at a programmable rate) n 2 selectable, fully programmable blink rates (frequency and duty cycle) between 0.148 Hz and 38 Hz (6.74 seconds and 0.026 seconds) n Input/outputs not used as LED drivers can be used as regular GPIOs n Internal oscillator requires no external components 2 n I C-bus interface logic compatible with SMBus n Internal power-on reset n Noise lter on SCL/SDA inputs n Active LOW reset input n 8 open-drain outputs directly drive LEDs to 25 mA n Edge rate control on outputsPCA9551 NXP Semiconductors 2 8-bit I C-bus LED driver with programmable blink rates n No glitch on power-up n Supports hot insertion n Low standby current n Operating power supply voltage range of 2.3 V to 5.5 V n 0 Hz to 400 kHz clock frequency n ESD protection exceeds 2000 V HBM per JESD22-A114, 150 V MM per JESD22-A115 and 1000 V CDM per JESD22-C101 n Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA n Packages offered: SO16, TSSOP16, HVQFN16 3. Ordering information Table 1. Ordering information T = - 40 C to +85 C. amb Type number Topside Package mark Name Description Version PCA9551D PCA9551D SO16 plastic small outline package 16 leads body width 3.9 mm SOT109-1 PCA9551PW PCA9551 TSSOP16 plastic thin shrink small outline package 16 leads SOT403-1 body width 4.4 mm PCA9551BS 9551 HVQFN16 plastic thermal enhanced very thin quad at package SOT629-1 no leads 16 terminals body 4 4 0.85 mm 4. Block diagram A0 A1 A2 PCA9551 INPUT REGISTER 2 SCL INPUT I C-BUS LED SELECT (LSn) FILTERS CONTROL REGISTER SDA 0 V 1 DD POWER-ON LEDn RESET RESET BLINK0 PRESCALER 0 PWM0 REGISTER REGISTER BLINK1 PRESCALER 1 PWM1 OSCILLATOR REGISTER REGISTER V SS 002aac504 Only one I/O shown for clarity. Fig 1. Block diagram of PCA9551 PCA9551 8 NXP B.V. 2008. All rights reserved. Product data sheet Rev. 08 31 July 2008 2 of 26