RT4539A

Copyright © 2022 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation

DS4539A-01

December 2022

www.richtek.com

25

Figure 10. LED Current (Dimming Down) vs. Fade Out Time

Normal Slope and Advanced Slope

Transition time between two brightness value can be controlled linearly by address 06h[5: 3] from 0 to 1024ms.

Same slope time is used for sloping up and down. With advanced slope, the brightness changes can be made more

smoothing to a human eye.

Table 12. Slope Time Control

Address Bit

Name

Default Value

Description

R/W

06h

[5:

3]

Slope Time Control

512ms

(B101)

B000: 0ms

B001: 1ms

B010: 8ms

B011: 128ms

B100: 256ms

B101: 512ms

B110: 768ms

B111: 1024ms

R/W

[7:

6]

Filter

medium

smoothing

(B10)

B00: No Filter (exponential)

B01: light smoothing

B10: medium smoothing

B11: heavy smoothing

R/W

Fade Out Time (Dimming Down)

49.95

50.00

50.05

50.10

50.15

50.20

50.25

0.0

0.5

1.0

1.5

2.0

2.5

Time (μs)

Brightness

(PWM)

Time

Brightness

(PWM)

Time

Slope Time

Light Smoothing

Medium Smoothing

Heavy Smoothing

Slope Input

PWM Output