PCA9551

Features:

• 8 LED drivers (on, off, flashing at a programmable rate)
• 2 selectable, fully programmable blink rates (frequency and duty cycle) between 0.148 Hz and 38 Hz (6.74 and 0.026 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
• Active-LOW reset input
• 8 open drain outputs directly drive LEDs to 25 mA
• Edge rate control on outputs
• No glitch on power-up
• Supports hot insertion
• Low stand-by current
• Operating power supply voltage range of 2.3 V to 5.5 V
• 0 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 JESDEC Standard JESD78 which exceeds 100 mA
• Packages offered: SO16, TSSOP16, HVQFN16


Pinout




Specifications

SYMBOL	PARAMETER	CONDITIONS	MIN	MAX	UNIT
VDD	Supply voltage		0.5	6.0	V
VI/O	DC voltage on an I/O		VSS 0.5	5.5	V
II/O	DC output current on an I/O		-	±25	mA
ISS	Supply current		-	100	mA
Ptot	Total power dissipation		-	400	mW
Tstg	Storage temperature range		65	+150	°C
Tamb	Operating ambient temperature		40	+85	°C

Description

The PCA9551 LED Blinker blinks LEDs in I2C-bus and SMBus applications where PCA9551 is necessary to limit bus traffic or free up the I2C Master's (MCU, MPU, DSP, chipset, 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 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 of PCA9551 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 ofPCA9551 not used for controlling the LEDs can be used for General Purpose Parallel Input/Output (GPIO) expansion.

The active-LOW hardware reset pin (RESET) PCA9551 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.