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Advice on part selection for ultra-low-noise high current source...

Nick de Smith
Intellectual 775 points
Other Parts Discussed in Thread: TPS7A47

Hi,

as part of a personal project, I'm looking to design an ultra-low-noise current source capable of delivering about 8-10A - it must be programmable in some form (DC voltage?) to set the current limit. Working voltage is in the range 0-20VDC. Required precision is not great - to the nearest 100mA would probably be fine.

Any thoughts on this would be appreciated - there are standard approaches using opamps + bypass FET/NPN but I was wondering what people's thoughts are.

Many thanks

Nick

  • 0
    TI__Guru 71526 points

    Hello Nick,

     Need some clarification, please.  Does the VOUT also have to be programmable?  You stated 0-20V, so do you need programmable 0-20V AND 8-10A programmability?  Or any voltage in the 0(?) > 20V range capable of delivering 8-10A in 100mA steps? 

    ANd when you say "ultra-low noise", what specification do you have in mind?

    I'm also moving this to the DC/DC Power Forum.

    ~Leonard

  • 0 in reply to LeonardEllis
    Intellectual 775 points

    Thanks for the reply - I'm looking at limiting Vout too, so yes - apologies for the vague thinking! Really, the supply will be operating in mostly CC mode rather than CV.

    Looking for lowest possible noise figures - don't have a specific value in mind, but low uV values certainly - ideally close to that of the TPS7A47...

  • 0 in reply to Nick de Smith
    TI__Expert 6620 points

    Nick,

    This is a lot of power.  Using a linear regulator seems to be a bad approach to me.  I would use a switching power supply with two control loops, one to control the max voltage and one to control the current.

    This article might help.

    Thanks,

    Robert

  • 0 in reply to Robert Taylor1
    Intellectual 775 points
    Thanks Robert - it's appreciated - I'll read that shortly - I was going to use a tracking SMPS buck-boost pre-regulator to reduce the power loss in the linear regulator - in my quest for lowest possible noise, I felt that a final linear stage would probably be better than any SMPS.

    My thinking is: Ideal diode bride -> SMPS buck/boost pre-regulation -> final linear stage -> output

    The SMPS would track to be slightly above the linear stage drop-out, thus minimising power dissipation in the linear section.

    Cheers