LP3944 Datasheet, PDF (1/12 Pages) National Semiconductor (TI) – RGB/White/Blue 8-LED Fun Light Driver

November 2003
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/I²C
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
n 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
n 8 LED driver (multiple programmable states — on, off,
input, and dimming at a specified rate)
n 8 Open drain outputs capable of driving up to 25 mA per
LED
Applications
n Customized flashing LED lights for cellular phones
n Portable Applications
n Digital Cameras
n Indicator Lamps
n General purpose I/O expander
n Toys
Typical Application Circuit
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