AS3675 datasheet(42/81 Pages) AMSCO

42 / 81 page

www.austriamicrosystems.com/AS3675

1v3

41 - 80

AS3675

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

Figure 23. PWM Control Circuit (currX_mode = 10b (PWM controlled)); X = any current sink

The adder logic (available for all current sinks) is intended to allow dimming not only from 0% to 100% (or 100% to 0%)

of currX_current, but also e.g. from 10% to 110% (or 110% to 10%) of currX_current. The starting current for up dim-

ming is defined by 0 + currX_adder and the end current is defined by currX_current + currX_adder.

An overflow of the internal bus (8 Bits wide to the IDAC) has to be avoided by the register settings (currX_current +

currX_adder must not exceed 255).

If the register subX_en is set, the result from the pwm modulator is inverted logically. That means for up dimming the

starting current is defined by currX_adder - 1 and the end current is defined by currX_adder - currX_current - 1. An

overflow of the internal bus (8 Bits wide to the IDAC) has to be avoided by the register settings (currX_adder -

currX_current - 1 must not be below zero).

Its purpose is to dim one channel e.g. CURR30 from e.g. 110% to 10% of curr30_current and at the same time dim

another channel e.g. CURR31 from 20% to 120% of curr31_current.

Note: The adder logic operates independent of the currX_mode setting, but its main purpose is to work together with

the pwm modulator (improved up/down dimming)

If the adder logic is not used anymore, set the bit currX_adder to 0. (Setting adder_currentX to 0 is not suffi-

cient)

At the end of up/down dimming, the pwm_code register keeps its final value (for up-dimming 255 and for down-

dimming 0). This can be used to identify the exact time, when up/down dimming is finished.

Table 56. 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

100,0

255

100,0

255

0,00s

0,000s

75,3

192

87,8

224

0,05s

0,03s

0,005s

0,003s

56,5

144

76,9

196

0,10s

0,05s

0,010s

0,005s

42,4

108

67,5

172

0,15s

0,08s

0,015s

0,008s

31,8

59,2

151

0,20s

0,10s

0,020s

0,010s

23,9

52,2

133

0,25s

0,13s

0,025s

0,013s

18,0

45,9

117

0,30s

0,15s

0,030s

0,015s

13,7

40,4

103

0,35s

0,18s

0,035s

0,018s

10,6

35,7

0,40s

0,20s

0,040s

0,020s

8,2

31,4

0,45s

0,23s

0,045s

0,023s

6,3

27,5

0,50s

0,25s

0,050s

0,025s

!!"

$ %!

% '

!& ! () )

* "!

AS3675

AS3675 датащи(PDF) 42 Page - ams AG

AS3675 датащи(HTML) 42 Page - ams AG

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81

датащи скачать

ссылки URL