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THS4551: PSRR CMRR curve ends at 10MHz! (also THS4552)

Merten Bausch
Prodigy 25 points
Part Number: THS4551
Other Parts Discussed in Thread: THS4552

Tool/software:

Dear TI,

could you please extend the CMRR and PSRR curves in the datasheets of THS4551 and THS4552 to 100MHz? The end is at 10MHz at 85dB (CMRR) and 80dB (PSRR, 5V). I need the values up to about 30MHz, 100MHz would be nice.

Under the curve is written: "simulated with G =1 V/V" (CMRR) and "simulated to differential output". Can I trust that these CMRR PSRR values are reached in the real usage of THS4551 or THS4552?

Thanks!

Merten

  • 0
    TI__Mastermind 24349 points

    Hello Merten,

    I can discuss your request with our validation team.  I will check our data repositories; some specifications are simulated and not measured.  In this case, it may be some time before updated value can be shared.

    Could you share your circuit so I can assist you?  We also offer SPICE models for simulation, which include CMRR and PSRR subcircuits.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 25 points

    Hello Alec,

    thanks in advance. Time is precious, I need to replace the LTC6362, for which there is no official package-compatible device. THS4551 could be a good and package-compatible replacement, but without a database of CMRR and PSRR I can not use it.

    Alec Saebeler said:
    Could you share your circuit so I can assist you?  We also offer SPICE models for simulation, which include CMRR and PSRR subcircuits.

    I don't need assistance in the schematics/pcb, the design works very well. It is almost the standard circurit you can find in every Differential-Opamp Datasheet, with gain=1 and Rf=750 Ohms. I am only searching a replacement Opamp.

    Maybe I could use the Simulation to get some information, but it is not the same quality of information as that provided by a datasheet. Maybe it's than easier to design a new pcb and use a not package compatible Opamp with specified CMRR and PSRR within my requirement.

    It would help me to get official data of CMRR and PSRR, otherwise the not availible data indicates to me, that THS4551 is not able to suppress interferences aboth 10MHz reliably.

    Thanks,

    Merten

  • 0 in reply to Merten Bausch
    TI__Mastermind 24349 points

    Hello Merten,

    I am working with my team to discuss PSRR & CMRR data.

    In the interim, please share if you have any issues or changes in performance when switching from LTC6362 to THS4551/2.

    Best,

    Alec

  • +1 in reply to Alec Saebeler
    TI__Mastermind 24349 points

    Hello Merten,

    I was able to find our team's data from THS4551/2 release, which happened to have data out to 100MHz.  In general it is not trivial or quick to find or measure such data, but it is good the data was already taken in years prior.  This does make the support of your request easier to fulfill Slight smile.

    Please see the attached PDF of the data:

    Datasheet_Plot_Extension_Request.pdf

    The data supports the understanding of a 20dB per decade roll-off of PSRR and CMRR, as would be expected.  You can continue with your design-in of THS4551/2 to replace LTC6362.

    Best,
    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 25 points

    Hello Alec,

    thanks. This plot is a statement. Obviously it is an ideal simulation with (as you mentioned) perfect 20dB per decade roll-off, so the simulation model is indistinguishable to a first order lowpass function ( f(w)=K/(1+j*w/w0) ). Real measurement data would be nice, but I assume that I will never get that, development of this opamp is obviously completed.

    Thank you for your quick commitment, and statement stays a statement. The plot shows 60dB at 30MHz (-5V PSRR) or even 73db (5V +PSRR), 40dB would be sufficient, so mission accomplished.

    Regards,

    Merten

  • 0 in reply to Merten Bausch
    TI__Mastermind 24349 points

    Hello Merten,

    I am glad this data assists in your evaluation.  If you do find issue or require bench support when adopting THS4551/2 into the design, I can assist with measurements as needed.  

    As long as the circuit solution performs as expected, there may not be a need for measurements.  However, if there is a difference in performance or a need t debug the circuit with THS4551/2, please revisit this thread or open a related one.

    Best,

    Alec