lt3086 - voltage output regulation with digital potentiometer

Hello,

I would like to use digipot to regulate output voltage in following circuit:

The regulation shall be allow the output from 0,4V -> 25V. Based on calculation, the resistance shall be from 0 to 0.5M. I can use the AD5293, but is has 100k max.

Is there any way to control output voltage with low voltage digipot? 

Im thinking about:

Extend Low-Voltage Digipot Resolution to Control an Adjustable Regulator | Electronic Design

but the set pin compare the expects to have 50uA current. Is there any other way to regulate voltage with this chip?

It is a part of power supply provided from 

Please advice how I can use digipot in above concept.

best regards

Maciek

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  • 0
    •  Analog Employees 
    on Apr 14, 2021 6:07 AM

    Hi Maciek,

    You have to use multiple AD5293 in series to achieve 500K ohm resistance.

    If you want to use a low voltage digipot, then you have to use amplifiers as attenuator before digipot and amplifier after digipot to get the right set voltage.

  • Hi Vsethia,

    any example how to build attenuator? should it attenuate the input of the digipot as I understand. Lets make simple attenuator using 2 extra resistors 200k each connected to A and B. Having 100k digipot between these resistors, when output voltage will be 24V, we got ~5V between A and B of digipot. But it is not 5V measured to GND. In that case how to power the digipot?

    best regards

    M.

  • 0
    •  Analog Employees 
    on Apr 15, 2021 4:44 AM in reply to MaciekM

    You need an In-Amp at LT3086 Vout to GND with an voltage divider at the In-Amp input that will trim the LT3086 Vout to within the digipot terminal voltage range.

    Use the IN-Amp VOUT pin to connect to Digipot terminals followed by a second stage amplifier to meet the LT3086 SET and VOUT range requirements.

Reply
  • 0
    •  Analog Employees 
    on Apr 15, 2021 4:44 AM in reply to MaciekM

    You need an In-Amp at LT3086 Vout to GND with an voltage divider at the In-Amp input that will trim the LT3086 Vout to within the digipot terminal voltage range.

    Use the IN-Amp VOUT pin to connect to Digipot terminals followed by a second stage amplifier to meet the LT3086 SET and VOUT range requirements.

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