LP3944

RGB/White/Blue 8-LED Fun Light Driver

General Description

LP3944 is an integrated device capable of independently

driving 8 LEDs. This device also contains an internal preci-

sion oscillator that provides all the necessary timing required

for driving each LED. Two prescaler registers along with two

PWM registers provide a versatile duty cycle control. The

LP3944 contains the ability to dim LEDs in SMBUS/I

applications where it is required to cut down on bus traffic.

Traditionally, to dim LEDs using a serial shift register such as

74LS594/5 would require a large amount of traffic to be on

the serial bus. LP3944 instead requires only the setup of the

frequency and duty cycle for each output pin. From then on,

only a single command from the host is required to turn each

individual open drain output ON, OFF, or to cycle a pro-

grammed frequency and duty cycle. Maximum output sink

current is 25 mA per pin and 200 mA per package. Any ports

not used for controlling the LEDs can be used for general

purpose input/output expansion.

Features

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Internal power-on reset

n

Active low reset

n

Internal precision oscillator

n

Variable dim rates (from 6.25 ms to 1.6s;

160 Hz–0.625 Hz)

Key Specifications

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8 LED driver (multiple programmable states — on, off,

input, and dimming at a specified rate)

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8 Open drain outputs capable of driving up to 25 mA per

LED

Applications

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Customized flashing LED lights for cellular phones

n

Portable Applications

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Digital Cameras

n

Indicator Lamps

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General purpose I/O expander

n

Toys

Typical Application Circuit

20085301

November 2003

© 2003 National Semiconductor Corporation

DS200853

www.national.com