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LT3090 output voltage controlled by DAC

Dear Sir/Madam,

I used the TPS7A3301 in an application where i adjusted the feedback voltage using a DAC. Vin=-30 and Vout=-27 to -28. It worked nicely however i ran into a problem with this part at these voltages that made the solution non viable.

I would like to use the LT3090 in the same application where the output voltage can be changed by using a DAC or something similar. Vin = -30 and Vout=-27 to -28V.

Page 15 of the DS mentions the following:

For applications requiring higher accuracy
or an adjustable output voltage, the SET pin may
be actively driven by an external voltage source
capable of sourcing 50μA – the application limitations
are the creativity and ingenuity of the circuit designer.

Any thoughts how to achieve this without impacting on the noise performance of the LDO?

Regards Joe

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  • Hi ARad,

    Thank you.

    I took a slightly different approach by using a active filter to reduce DAC noise.
    The DAC is represented by a voltage source 0 to +2V048.
    The output of the OPA376 swings 0 to -2V048.
    The +-2V5 rails power up first and the DAC output powers up at 0V.

    Do you see any issues with this circuit?

    Regards Joe