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Change feedback resister dinamically

Kai Nomiyama
Expert 5285 points

Hi Team,

I have general question about changing feedback resister.

DCDC has external feedback resiter to set output voltage.

If we change resister value e.g. from AΩ to BΩ while DCDC is working, are there any problem?

What my customer wants to do is below

24Vin

--> 6V/400mA out

--> 10V/800mA out

feedback resister is changed by external FET.

Please let me know if you have any concern?

Thanks,

Regards,

Kai

  • 0
    TI__Guru**** 191445 points

    generally speaking you can do that.  For large output voltage changes you may see some overshoot or undershoot on the transition, depending on how fast the FET switches.  Also, this works better using voltage mode control as the lower feedback resistor is not part of the small signal loop.  If you use current mode control, make sure the compensation works for both 6 V and 10 V cases.