AS3677 datasheet(31/68 Pages) AMSCO

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AS3677

Datasheet - D e ta i l e d D e s c r i p t i o n

PWM Generator Registers

3,5

1,45s

0,73s

0,145s

0,073s

3,1

1,50s

0,75s

0,150s

0,075s

2,7

1,55s

0,78s

0,155s

0,078s

2,4

1,60s

0,80s

0,160s

0,080s

2,0

1,65s

0,83s

0,165s

0,083s

1,6

1,70s

0,85s

0,170s

0,085s

1,2

1,75s

0,88s

0,175s

0,088s

0,8

1,80s

0,90s

0,180s

0,090s

0,4

1,85s

0,93s

0,185s

0,093s

0,0

1,90s

0,95s

0,190s

0,095s

Table 37. Pwm control

Addr: 16h

Pwm control

This register controls PWM generator

Bit

Bit Name

Default Access

Description

2:1

pwm_dim_mode

00b

R/W

Selects the dimming mode

00b

no dimming; actual content of register

pwm_code is used for pwm generator

01b

logarithmic up dimming (codes are increased).

Start value is actual pwm_code

10b

logarithmic down dimming (codes are

decreased). Start value is actual pwm_code;

switch off the dimmed current source after

dimming is finished to avoid unnecessary

quiescent current

11b

5:3

pwm_dim_speed

000b

R/W

Defines dimming speed by increase/decrease pwm_code

000b

by 1/4

th every 50 msec (total dim time 1.0s)

001b

by 1/8

th every 50 msec (total dim time 1.9s)

010b

by 1/4

th every 25 msec (total dim time 0.5s)

011b

by 1/8

th every 25 msec (total dim time 0.95s)

100b

by 1/4

th every 5 msec (total dim time 100ms)

101b

by 1/8

th every 5 msec (total dim time 190ms)

110b

by 1/4

th every 2.5 msec (total dim time 50ms)

111b

by 1/8

th every 2.5 msec (total dim time 95ms)

Table 36. PWM Dimming Table

Decrease by 1/4th

every step

Decrease by 1/8th

every step

Seconds

Step

%Dimming

PWM

%Dimming

PWM

50msec/

Step

25msec/

Step

5msec/

Step

2.5msec/

Step

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