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THS4521EVM gerbers

Jonathan Edelson
Prodigy 60 points

Other Parts Discussed in Thread: THS4521, THS4551

This question is a followup to: https://e2e.ti.com/support/data_converters/precision_data_converters/f/73/t/527356  

1) Are gerbers available for the THS4521EVM, described in this datasheet: http://www.ti.com/lit/ug/sbou080/sbou080.pdf 

2) Is there a suggested layout for the decoupling capacitors when the amplifier is used with a single supply, per the circuit on the first page of the datasheet?

Many thanks,

Jonathan Edelson

  • 0
    TI__Genius 13935 points

    Hi Jonathan,

    I will try to locate the THS4521 GERBER files for you. 


    For single supply the decoupling capacitors should be near the V+ pin and should have low impedance vias to the ground plane.We recommend continuous planes for both V+ and Ground. 

    Regards,

    Loren

  • 0 in reply to Loren Siebert 1
    Prodigy 60 points
    Many thanks. I could not add the following until after my post was 'moderated', however after asking my question I became aware of the THS4551 device, which is available in a pin compatible version to the THS4521.

    The gerbers for the THS4551EVM would be a perfect substitute for the THS4521 gerbers.

    All the best,
    Jonathan Edelson
  • 0 in reply to Jonathan Edelson
    TI__Genius 13935 points

    THS4521_GERBERS.zipHi Johnathon,

    Our PCB designer sent me the GERBER files for the THS4521.  If you want the THS4551 I could get those as well.

    Regards,

    Loren

  • 0 in reply to Loren Siebert 1
    Prodigy 60 points

    Thanks again!  The THS4521 gerbers are sufficient; now I can see clearly the layout described in the datasheet.   I do not need the THS4551 gerbers.

    I do have an additional question.  I am trying to understand the layout requirement (datasheet http://www.ti.com/lit/ds/sbos458h/sbos458h.pdf section 11.1) that power and ground planes should be removed below input and output pins.  

    The EVM gerber is for dual supply use, and shows the ground planes removed from under _all_ the pins and from under the decoupling capacitors.  What is the recommended ground and power plane removal layout for single supply operation?  Should the ground and power planes be removed on the Vs- side? Should they only be removed from under the input and output pins, or over a larger area?

    Regards,

    Jonathan Edelson

  • 0 in reply to Jonathan Edelson
    TI__Genius 13935 points

    Hi Jonathan,

    The goal of removing the power and ground planes from under the Vout pin and the Inverting input pin are to reduce the capacitance on these pins.  They are the most sensitive pins to parasitic capacitance.  On the inverting input pin any parasitic capacitance will increase gain at high frequencies, on the output pin parasitic capacitance delays the feedback signal and directly contributes to reduced phase margin.  Both of these effects can be minimized by reducing the amount of metal that is near these pins.  (Note that for an FDA both inputs are inverting inputs). 

    For small packages it is difficult to remove such small areas, so the cut out material may extend to other device pins as well. 

    For single supply parts there is one less power connection, but the overall concept is the same, to remove metal from near the output pin and the inverting input pin. 

    Regards,

    Loren

     

  • 0 in reply to Loren Siebert 1
    Prodigy 60 points
    Perfect. I am generating a layout based on the above.
    All the best,
    Jonathan Edelson