LP5012 datasheet(14/51 Pages) TI

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8 Bits Brightness

Brightness Control

Linear OR Logarithmic

Log_Scale_EN

Figure 8-2. Logarithmic- or Linear-Scale Intensity Control

255

128

160

192

224

LEDx_BRIGHTNESS Register Input

Linear Scale Dimming Curve

LEDx_BRIGHTNESS Register Input

Logarithmic Scale Dimming Curve

100%

80%

60%

40%

20%

100%

80%

60%

40%

20%

128

160

192

224

255

Figure 8-3. Logarithmic vs Linear Dimming Curve

8.3.1.3 12-Bit, 29-kHz PWM Generator Per Channel

8.3.1.3.1 PWM Generator

With the inputs of the color mixing and the intensity control, the final output PWM duty cycle is defined as the

product obtained by multiplying the color-mixing register value by the related intensity-control register value. The

final output PWM duty cycle has 12 bits of control accuracy, which is achieved by a 9 bits of pure PWM

resolution and 3 bits of digital dithering control. For 3-bit dithering, every eighth pulse is made 1 LSB longer to

increase the average value by 1 / 8th. The LP50xx device allows users to enable or disable the dithering function

through the PWM_Dithering_EN register. When enabled (default), the output PWM duty-cycle accuracy is 12

bits. When disabled, the output PWM duty-cycle accuracy is 9 bits.

To eliminate the audible noise due to the PWM switching, the LP50xx device sets the PWM switching frequency

at 29 kHz, above the 20-kHz human hearing range.

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

LP5009, LP5012

SLVSEH2B – MAY 2019 – REVISED AUGUST 2020

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