PCA9550 datasheet(2/17 Pages) PHILIPS

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Philips Semiconductors

Product data

PCA9550

2-bit I2C LED driver with

programmable blink rates

2003 May 02

FEATURES

• 2 LED drivers (on, off, flashing at a programmable rate)

• 2 selectable, fully programmable blink rates (frequency and duty

cycle) between 0.15625 and 40 Hz (6.4 and 0.025 seconds)

• Input/output 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

• 2 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 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 JEDEC Standard JESD78 which

exceeds 100 mA

• Packages offered: SO8, TSSOP8

DESCRIPTION

The PCA9550 LED Blinker blinks LEDs in I2C-bus and SMBus

applications where it 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 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.

PIN CONFIGURATION

LED0

LED1

VSS

VDD

SDA

SCL

RESET

SW00926

Figure 1. Pin configuration

PIN DESCRIPTION

NUMBER

SYMBOL

FUNCTION

Address input 0

LED0

LED driver 0

LED1

LED driver 1

VSS

Supply ground

RESET

Active-LOW reset input

SCL

Serial clock line

SDA

Serial data line

VDD

Supply voltage

ORDERING INFORMATION

PACKAGES

TEMPERATURE RANGE

ORDER CODE

TOPSIDE MARK

DRAWING NUMBER

8-Pin Plastic SO

-40 to +85

°C

PCA9550D

PCA9550

SOT96-1

8-Pin Plastic TSSOP

-40 to +85

°C

PCA9550DP

9550

SOT505-1

Standard packing quantities and other packaging data is available at www.philipslogic.com/packaging.

I2C is a trademark of Philips Semiconductors Corporation.

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