LP5018 datasheet(13/49 Pages) TI1

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Phase 1

Phase 2

Phase 3

Cycle Time

Phase 1

Phase 2

Phase 3

LED1

LED4

LED22

LED0

LED3

LED21

LED2

LED5

LED23

LP5018, LP5024

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SLVSEB8 – MARCH 2018

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Feature Description (continued)

8.3.1.4 PWM Phase-Shifting

A PWM phase-shifting scheme allows delaying the time when each LED driver is active. When the LED drivers

are not activated simultaneously, the peak load current from the pre-stage power supply is significantly

decreased. The scheme also reduces input-current ripple and ceramic-capacitor audible ringing. LED drivers are

grouped into three different phases.

•

Phase 1—the rising edge of the PWM pulse is fixed. The falling edge of the pulse is changed when the duty

cycle changes. Phase 1 is applied to LED0, LED3, …, LED21.

•

Phase 2—the middle point of the PWM pulse is fixed. The pulse spreads in both directions when the PWM

duty cycle is increased. Phase 2 is applied to LED1, LED4, …, LED22.

•

Phase 3—the falling edge of the PWM pulse is fixed. The rising edge of the pulse is changed when the duty

cycle changes. Phase 3 is applied to LED2, LED5, …, LED23.

Figure 7. PWM Phase-Shifting

8.3.2 LED Bank Control

For most LED-animation effects, like blinking and breathing, all the RGB LEDs have the same lighting pattern.

Instead of controlling the individual LED separately, which occupies the microcontroller resources heavily, the

LP50xx device provides an easy coding approach, the LED bank control.

Each channel can be configured as either independent control or bank control through the LEDx_Bank_EN

brightness-control registers. When LEDx_Bank_EN = 1, the LP50xx device drives the LEDs in LED bank-control

mode. The LED bank has its own independent PWM control scheme, which is the same structure as the PWM

scheme of each channel. See PWM Control for Each Channel for more details. When a channel is configured in

LED bank-control mode, the related color mixing and brightness control is governed by the bank control registers

(BANK_A_COLOR, BANK_B_COLOR, BANK_C_COLOR, and BANK_BRIGHTNESS) regardless of the inputs

on its own color-mixing and brightness-control registers.

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