LED171596ARSLR datasheet(17/153 Pages) TI1

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Time

Sloper Input

Sloper Output

Slope Time

Linear Slope

Advanced Slope

LEDxx PWM Brightness = ledgrp[1...3]_bri

ledxx_bri

master_bri

LED171596A

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SNVSAY2 – OCTOBER 2017

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7.3.3.1.4

Group Brightness Control Method

The group brightness control is used to select LEDs into 1 to 3 groups where each group has a separate register

for brightness control. Every LED has 2-bit selection register LEDxx_GRPSEL to select whether or not it belongs

to one of the three groups:

•

00 – Not a member of any group

•

01 – Member of group 1

•

10 – Member of group 2

•

11 – Member of group 3

The brightness level for each group is controllable with the LED_GRP1_BRI, LED_GRP2_BRI and

LED_GRP3_BRI registers. The matrix sloper does not affect any LEDs that are assigned to these three groups.

The master brightness register (MASTER_BRI) affects all LEDs regardless of group selection as shown in

Equation 4.

(4)

7.3.3.2 Sloper

Two optional sloper functions create smooth transitions from one brightness value to another. One sloper

operates for master brightness changes, and the second sloper can be assigned to any individual LED or group

of LEDs using the LEDxx_slope bits.

Sloper transition time between two brightness values is programmed with register bits master_slope_select[1:0]

and matrix_slope_select[1:0]. For 2-ms and 10-ms durations the sloper is linear. For 50-ms and 200-ms

durations the sloper uses a curve-bending function to produce a brightness transition that appears visually

smoother. Further, a master_slope_en[0] bit is used to disable the function for the master sloper. To disable the

matrix sloper, all the LEDxx_slope bits can be set to 0. The sloper_matrix_done and sloper_master_done bits are

set once the sloper is complete.

The master sloper may be interrupted with a new brightness change, and it restarts from current brightness and

begins sloping to new brightness target. The matrix sloper must finish before being used again for a new

brightness level or different group of LEDs. While the matrix sloper is in progress any LEDs that were assigned

to the sloper continue to follow the sloper output and are not updated by a new LATCH event. All other registers

of LEDs not assigned to an in-progress matrix sloper can be updated and LATCHED normally.

Figure 14. Master Sloper

LED171596ARSLR Datasheet(PDF) 17 Page - Texas Instruments

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