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LP5560

SNVS873D – AUGUST 2012 – REVISED JUNE 2016

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7.3.5 Rise and Fall Time Settings

Rise and fall times of each pulse can be programmed independently. Rise and fall time can be set from 0 to

1584 ms with 105.6 ms steps. Rise and fall times are generated using a combined PWM and current control.

Ramp has 32 PWM steps. For the first 8 steps LED current is decreased to 12.5%. For the remaining steps

current is set to 100%. Each step is 3.3 ms long. This results in the minimum ramp time of 3.3 ms × 32 = 105.6

ms. When ramp time is increased each PWM step is done multiple times. When setting rise and fall times they

are always rounded down. For example if calibration pulse length is 1 ms and rise time setting pulse is 2.9 ms

rise time is set to 2 which is 211.2 ms. Rise and fall times can be set to zero by giving pulse that is shorter than

calibration pulse.

Table 3. Rise and Fall Time Settings

RAMP SETTING

RAMP TIME (ms)

0

0

1

105.6

2

211.2

3

316.8

4

422.4

5

528 default

6

633.6

7

739.2

8

844.8

9

950.4

10

1056

11

1161.6

12

1267.2

13

1372.8

14

1478.4

15

1584