AS3665 datasheet(16/78 Pages) AMSCO

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AS3665

Datasheet, Confidential - D e ta i l e d D e s c r i p t i o n C u r r e n t S o u r c e s

Current Sources

The internal circuit of the current sources is shown in Figure 18 (one current source shown; internally there are 9 iden-

tical blocks):

Figure 18. Current Sources

The processing path consists of the following step (using current source 1 as example):

1. The input of the complete current source block is the register pwm_LED1 (see page 22). This register can be

controlled by I

2C directly or by any of the three sequencers (see section Sequencers on page 48).

2. The signal is converted from logarithmic domain to linear domain (depending on signal loglin1 (see page 25))

or multiplied by 16 to obtain 12 bits.

3. It passes an adjustable fader (it can be multiplied by any of the fader registers fader1, fader2 or fader3). If

fader_src1 (see page 25)=0, the fader is not used (signal is unchanged).

4. Color correction is performed (temp_int_ext (see page 24) selects either internal temperature measurement or

use the register led_temp (see page 24)). The gain of the color correction can be adjusted by color_slope1

(see page 25). If color_slope1=0, color correction is disabled.

5. The resulting 12 bit signal goes to the PMW generator and then to the current source itself.

6. The current source is enabled by LED1_on

5 and its current is adjusted by LED_current1 and LED1_max.

5. LED1_on...LED9_on have only effect if all sequencer are switched off (p1_en (see page 46)=00 and

p2_en=00 and p3_en=00). This allow direct control of the LEDs if no program is executed.

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AS3665

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