LP38691-ADJ: Programmable output voltage

HI Are,

Sure. You can use a digital potentiometer as R2

The key is to make sure that the total series resistance (R1+R2) is less than 100K. 

Does this answer your question?

HI Are,

Sure. You can use a digital potentiometer as R2

The key is to make sure that the total series resistance (R1+R2) is less than 100K. 

Does this answer your question?

Hi Art,

To be safe, the sum total of R1+R2 should be less than 100K. If it is more than this the input leakage into the ADJ pin could impact regulation accuracy. I would recommend using R3, R5, R6(R2), and R8 at 1/10th the current value.

Regards,

John

Hi Art,

I think this is how you would hook it up. This should allow you to sweep the output voltage from 1.25V up to 5.5V:

If VIN of the LP38691 is greater than 5.5V, then the H pin of the potentiometer should be connected to a 5V rail or lower. 

You may want to confirm with the data converter team or at a minimum order an EVM for both to try it out.

I hope this helps.

Hi Art,

No. An analog potentiometer can be connected directly between the FB pin and GND. I think this is a better approach.

If you want simple digital control, the Any-Out(TM) feature with a device like the TPS7A83. The Any-Out pins connected to GND simply add to the reference. So with an open-drain MCU or GPIO expander, you can sweep VOUT from 0.8 to 3.85V in 50mV steps. 

Let me know what you think.