PCA9550
2
2-bit I C-bus LED driver with programmable blink rates
Rev. 05 13 October 2008 Product data sheet
1. General description
2
The PCA9550 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 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
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the amount of trafc on the I C-bus and uses up one of the master's timers. The PCA9550
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.
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).
One hardware address pin on the PCA9550 allows two devices to operate on the same
bus.
2. Features
n 2 LED drivers (on, off, ashing at a programmable rate)
n 2 selectable, fully programmable blink rates (frequency and duty cycle) between
0.172 Hz and 44 Hz (5.82 seconds and 0.023 second)
n Input/output not used as LED drivers can be used as regular GPIOs
n Internal oscillator requires no external components
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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 2 open-drain outputs directly drive LEDs to 25 mA
n Controlled edge rates to minimize ground bounce
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 kHz to 400 kHz clock frequencyPCA9550
NXP Semiconductors
2
2-bit I C-bus LED driver with programmable blink rates
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: SO8, TSSOP8 (MSOP8), HVSON8
3. Ordering information
Table 1. Ordering information
Type number Package
Name Description Version
PCA9550D SO8 plastic small outline package; 8 leads; body width 3.9 mm SOT96-1
[1]
PCA9550DP TSSOP8 plastic thin shrink small outline package; 8 leads; body width 3 mm SOT505-1
PCA9550TK HVSON8 plastic thermal enhanced very thin small outline package; no leads; 8 terminals; SOT908-1
body 3 3 0.85 mm
[1] Also known as MSOP8.
3.1 Ordering options
Table 2. Ordering options
Type number Topside mark Temperature range
PCA9550D PCA9550 T = - 40 C to +85 C
amb
PCA9550DP 9550 T = - 40 C to +85 C
amb
PCA9550TK 9550 T = - 40 C to +85 C
amb
4. Block diagram
A0
PCA9550
INPUT
REGISTER
SCL 2
INPUT I C-BUS
LED SELECT (LS0)
FILTERS CONTROL
REGISTER
SDA
0
1
V
DD
POWER-ON
LEDn
RESET
RESET
BLINK0
PRESCALER 0 PWM0
REGISTER REGISTER
BLINK1
PRESCALER 1 PWM1
OSCILLATOR
REGISTER REGISTER
V
SS
002aad241
Only one I/O shown for clarity.
Fig 1. Block diagram of PCA9550
PCA9550_5 NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 05 13 October 2008 2 of 26