Electronics > PCB/EDA/CAD

Linear Regulator Output Adjustment

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joniengr081:
Hello,

I am wondering about Digital Potentiometer DS1868B in order to adjust the output voltage of a Linear Regular using voltage divider. Let's suppose I have a Linear Regulator with a fixed output of 3.3 V and the Linear Regulator can deliver or support 1.5 A load current.

If the load requirement I my design is variable between 2.5 V to 3.0 V with current approximately 1 A. Can I use Digital Potentiometer DS1868B in a voltage divider such that I can adjust the output voltage by Digital Potentiometer DS1868B through FPGA ?

How much current will run through the voltage divider resistors ? Do I need to care about power rating of the resistors used in the voltage divider ?

xvr:

--- Quote ---Can I use Digital Potentiometer DS1868B in a voltage divider such that I can adjust the output voltage by Digital Potentiometer DS1868B through FPGA ?
--- End quote ---
You can't use Digital Potentiometer as direct divider between output of LDO and load because current capacity of DP is quite low (mA ranges).
You can't use DP in feedback/ground circuit of LDO because any divider here can also increase output voltage of LDO, but you need to decrease it.
You can create buffered (by transistor) divider between LDO output and load, but it will be roughly the same as adding another one LDO to already existing one.

joniengr081:
The third option you mentioned with transistor. Can I also invert the voltage as well ? But this will be a fixed output. I am wondering how can I control the voltage level through FPGA. I also need to make it adjustable.

xvr:
No, transistor can't invert output - it used as simple follower. For digital control of output can be used various regulators (both liner and switched mode) and even trivial opamp circuit. It depends on requirements for current and stability. There are a set of regulator with direct digital control also exist.

joniengr081:
Thanks for your comment. Do you mean linear regulator with digital control through FPGA. I am not aware of. Kindly give me some example because this is exactly what I am looking for.

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