DAC53508 datasheet(26/40 Pages) TI1

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8.2.1.2 Detailed Design Procedure

The DAC is used to set the source current of a MOSFET using a unity-gain buffer, as shown in Figure 8-1.

Connect the LED between the power supply and the drain of the MOSFET. This configuration allows the DAC

to control or set the amount of current through the LED. The buffer following the DAC controls the gate-source

voltage of the MOSFET inside the feedback loop, thus compensating this drop and corresponding drift due to

temperature, current, and ageing of the MOSFET. The current set by the DAC that flows through the LED is

calculated with Equation 2. To generate 0 mA to 20 mA from a 0 V to 5 V DAC output range, a 250-Ω RSET is

required.

ISET=VDACRSET

(2)

The following pseudocode is provided to help get started with the LED biasing application:

//SYNTAX: WRITE <REGISTER NAME(Hex Code)>, <DATA>

//Power-up the device and channels

WRITE DEVICE_CONFIG(0x01), 0x0000

//Program mid code (or the desired voltage) on all channels

WRITE DACA_DATA(0x08), 0x07FC //10-bit MSB aligned

WRITE DACB_DATA(0x09), 0x07FC //10-bit MSB aligned

WRITE DACC_DATA(0x0A), 0x07FC //10-bit MSB aligned

WRITE DACD_DATA(0x0B), 0x07FC //10-bit MSB aligned

WRITE DACE_DATA(0x0C), 0x07FC //10-bit MSB aligned

WRITE DACF_DATA(0x0D), 0x07FC //10-bit MSB aligned

WRITE DACG_DATA(0x0E), 0x07FC //10-bit MSB aligned

WRITE DACH_DATA(0x0F), 0x07FC //10-bit MSB aligned

8.2.1.3 Application Curve

Figure 8-2. DC Transfer Characteristics of LED Biasing Circuit

DAC43508, DAC53508, DAC63508

SLASF08A – DECEMBER 2021 – REVISED MAY 2024

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DAC53508 Datasheet(PDF) 26 Page - Texas Instruments