-40

80

TEMPERATURE (°C)

-10

-5

0

5

10

60

40

20

0

-20

LP3943

www.ti.com

SNVS256A – MAY 2004 – REVISED MAY 2004

Electrical Characteristics (continued)

(1)

Limit

Symbol

Parameter

Conditions

Typical

Units

Min

Max

Maximum Pulse Width of Spikes

(3)

that Must Be Suppressed by the

50

ns

Input Filter of Both DATA & CLK

Signals

Typical Performance Characteristics

Frequency vs. Temp

Application Notes

THEORY OF OPERATION

The LP3943 takes incoming data from the baseband controller and feeds them into several registers that control

the frequency and the duty cycle of the LEDs. Two prescaler registers and two PWM registers provide two

individual rates to dim or blink the LEDs (for more information on these registers, refer to Table 3). Each LED

can be programmed in one of four states—on, off, DIM0 rate or DIM1 rate. Two read-only registers provide

status on all 16 LEDs. The LP3943 can be used to drive RGB LEDs and/or single-color LEDs to create a colorful,

entertaining, and informative setting. Alternatively, it can also drive RGB LED as a flashlight. This is particularly

suitable for accessory functions in cellular phones and toys. Any LED pins not used to drive LED can be used for

General Purpose Parallel Input/Output (GPIO) expansion.

To bring the LP3943 into reset, hold the RST pin LOW for a period of TW. This will put the chip into its default

state. The LP3943 can only be programmed after RST signal is HIGH again.

The data on SDA line must be stable during the HIGH period of the clock signal (SCL). In other words, state of

the data line can only be changed when CLK is LOW.

Copyright © 2004, Texas Instruments Incorporated

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