255

0

32

64

96

128

160

192

224

LEDx_BRIGHTNESS Register Input

Linear Scale Dimming Curve

0

LEDx_BRIGHTNESS Register Input

Logarithmic Scale Dimming Curve

100%

80%

60%

40%

20%

0%

100%

80%

60%

40%

20%

0%

32

64

96

128

160

192

224

255

8 Bits Brightness

8 Bits Brightness

Brightness Control

Linear OR Logarithmic

Linear OR Logarithmic

Log_Scale_EN

11

LP5009, LP5012

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SLVSEH2 – MAY 2019

Product Folder Links: LP5009 LP5012

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Copyright © 2019, Texas Instruments Incorporated

Feature Description (continued)

Figure 3. Logarithmic- or Linear-Scale Intensity Control

Figure 4. 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.