LP5009 datasheet(12/52 Pages) TI2

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8 Detailed Description

8.1 Overview

The LP50xx device is an 9- or 12-channel constant-current-sink LED driver. The LP50xx device includes all

necessary power rails, an on-chip oscillator, and a two-wire serial I2C interface. The maximum constant-current

value of all channels is set by a single external resistor. Two hardware address pins allow up to four devices on

the same bus. An automatic power-saving mode is implemented to keep the total current consumption under 10

µA, which makes the LP50xx device a potential choice for battery-powered end equipment.

The LP50xx device is optimized for RGB LEDs regarding both live effects and software efforts. The LP50xx

device controls each LED output with 12-bit PWM resolution at 29-kHz switching frequency, which helps achieve

a smooth dimming effect and eliminates audible noise. The independent color-mixing and intensity-control

registers make the software coding straightforward. When targeting a fade-in, fade-out type breathing effect, the

global RGB bank control reduces the microcontroller loading significantly. The LP50xx device also implements a

PWM phase-shifting function to help reduce the input power budget when LEDs turn on simultaneously.

8.2 Functional Block Diagram

OUT0

VLED

12 Bits

29 kHz

PWM

Generators

VCC

Bandgap

IREF Setting Current

Digital

Interface

V1P8

LDO

Digital Control

Oscillator

15MHz

Thermal Shutdown

OUT1

OUT2

OUT9

OUT10

OUT11

GND

VCC

VCAP

SDA

SCL

ADDR0

ADDR1

IREF

8.3 Feature Description

8.3.1 PWM Control for Each Channel

Most traditional LED drivers are designed for the single-color LEDs, in which the high-resolution PWM generator

is used for intensity control only. However, for RGB LEDs, both the color mixing and intensity control must be

addressed to achieve the target effect. With the traditional solution, the users must handle the color mixing and

intensity control simultaneously with a single PWM register. Several undesired effects occur: the limited dimming

steps, the complex software design and the color distortion when using a logarithmic scale control.

The LP50xx device is designed with independent color mixing and intensity control, which makes the RGB LED

effects fancy and the control experience straightforward. With the inputs of the color-mixing register and the

intensity-control register, the final PWM generator output for each channel is 12-bit resolution and 29-kHz

dimming frequency, which helps achieve a smooth dimming effect and eliminates audible noise. See Figure 8-1.

LP5009, LP5012

SLVSEH2B – MAY 2019 – REVISED AUGUST 2020

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