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AS3820

16-Channel White LED Controller for LCD Backlight

Rev. 1.1

Datasheet

www.dialog-semiconductor.com

34 of 52

05-Feb-2019

8.4 Power Supply

8.4.1 Voltage Regulator V3_2

A build in linear voltage regulator provides 3.2V supply voltage for external devices at pin V3_2. A 2.2μF decoupling

capacitor should be connected to pin V3_2.

8.4.2 Interface Power Supply V3_2

Pin V3_2 supplies all digital inputs/outputs.

8.5 Safety Features

8.5.1 Temperature Shutdown

If “autotoff_ot” = 1 the outputs of the device are turned OFF when the die temperature reaches 140°C. If the die

temperature goes below 130°C the outputs are turned ON again.

8.5.2 Register Lock/Unlock

To prevent wrong writing to registers due to noise on the seria interface a lock/unlock mechanism is implemented.

Group1 and can only be written if Group1 is unlocked by the “LOCKUNLOCK”-byte (Reg: 0x36)

“LOCKUNLOCK”-byte (Reg: 0x36)

The default value of the Groups is locked.

8.6 Dynamic Feedback Control

The output of pins “FB1” and “FB2” can be used to control any external power supply for best power efficiency.

Every power supply senses its output voltage with a resistive voltage divider. This voltage divider can be modified to

set the output voltage between a minimum output voltage VMIN and a maximum output voltage VMAX. The design of

the dynamic feedback control is done in 2 steps.

Step 1: Calculate resistors R1 in order to achieve the desired voltage range (VMAX – VMIN) with 255μA maximum

current DAC output.

Figure 8.13 : Step 1

VoutMAX – VoutMIN

R1 = _________________

255μA

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