AS3693B1

austriami crosyst ems

www.austriamicrosystems.com

Revision 1.26 / 2011-04-02

10 - 33

7

Block Description

7.1 Feedback Circuit

The AS3693B1 supports a flexible feedback selection for external DCDC – supplies. Beside the default setup for

RGGB lighting, each channel can be assigned to an external DCDC feedback loop. This feedback circuit is

important to reduce power dissipation of the device.

Table 6 – Feedback Control

Addr: 04h

Feedback control

Enables and Disables the Different Feedback modes

Bit

Bit Name

Default

Access

Description

0

Feedback on

1

R/W

1 = Feedback Circuit is active

0 = The entire Feedback Loop is disabled

1

Feedback on PWM

0

R/W

0 = The Feedback Regulator is always active

1 = The Feedback Regulator is only active, if PWM = 1

2

Open_Led_Det_on

0

R/W

Enables open Led Detection Comparators

0 = Open Led Detection Disabled

1 = Open Led Detection Enabled

3

Short_det_on

0

R/W

Enables Short detection

0 = Short detection off

1 = Sort detection on

5:4

VS_L

00

R/W

Short led Detection Voltage ( debounced 3mS )

Detection voltage is defined by Addr 0x58h bit[1:0] and

Addr 0x04 bit[5:4] and the DAC output voltage

Addr 0x58h

Addr 0x04h

bit]1] bit[0]

bit]5] bit[4]

CODE

0 0

0 0

= 3

0 0

0 1

= 5

0 0

1 0

= 0

0 0

1 1

= 1

0 1

0 0

= 6

0 1

0 1

= 7

0 1

1 0

= 2

0 1

1 1

= 4

1 0

0 0

= 10 do not use ( >11V)

1 0

0 1

= 11 do not use ( >11V)

1 0

1 0

= 8

1 0

11

=

9

do not use ( >11V)

The short led detection voltage can be calculated:

Vshort = 5*(0.6 + 0.2*CODE ) - 4*Vdac

The resulting voltage Vshort must be <= 11V

7:6

DCDC_Regulation_tri

p Point (VC)

00

R/W

Trip Point voltage of the DCDC-Feedback Regulation

Circuit. (NOTE: This value has to be adjusted if Analog

Ref select Bit is changed.)

00 = 0.5V (Note use for Currents up to 70 mA)

01 = 0.6V (Note use for Currents up to 80 mA)

10 = 0.8V (Note use for Currents up to 110 mA)

11 = 1.0V (Note use for Currents up to 150 mA)

Table 6a – Short Detect High

Addr: 58h

Short LED High

High bits of short led detection voltage

Bit

Bit Name

Default

Access

Description

1:0

VS_H

00

R/W

Short led Detection Voltage ( debounced 3mS )

Detection voltage is defined by Addr 0x58h bit[1:0] and

Addr 0x04 bit[5:4] ( see Addr. 0x04 definition )