6 Detailed Description

6.1 Overview

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 6-1). 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.

The LP3943 is equipped with power-on reset that holds the chip in a reset state until VDD reaches VPOR during

power up. Once VPOR is achieved, the LP3943 comes out of reset and initializes itself to the default state.

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

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

6.2 Functional Block Diagram

Prescaler 0

Register

PWM 0

Register

Oscillator

Power-On Reset

VDD

RST

0

1

LED0

0

1

LED15

Bit 7 of Select Register LS3

Bit 6 of Select Register LS3

Bit 7 of Input Register2

PWM0 Register

PWM1 Register

COPIES

Bit0 of

Select

Register

LED Select Register

Bit1

Input Register

Bit0 of Input Reg 1

I

2C Bus

Control

I

2C

Filters

A2 A1 A0

SCL

SDA

LS0

Prescaler 1

Register

PWM 1

Register

LP3943

SNVS256E – NOVEMBER 2003 – REVISED OCTOBER 2024

www.ti.com

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