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ADC14155QML

Stephen Mitchell
Prodigy 100 points
Other Parts Discussed in Thread: ADC14155QML-SP, THS4513-SP, THS4511-SP, THS4511, THS4513, ADS5463-SP, THS4509, ADS5463

I need some help finding an Op Amp to drive the ADC14155QML-SP. The op Amp must receive a single-ended signal and provide differential outputs with a Vcm of 1.5V to be compatible with the ADC14155QML-SP. The single-ended input signal to the Op Amp is a log video signal so I need to use a DC coupled interface so i don't distort rise times of the pulses. Lastly, it needs to be a QML component for this application.

Thanks,

 

  • 0
    TI__Genius 17125 points

    Hello Stephen,

    Please see the THS4513-SP.  That along with the THS4511-SP are the two space qualified, radiation tested differential op amps that TI offers.

    The TI space products can be found at the following website:

    http://www.ti.com/hirel/docs/productcontent.tsp?sectionId=603&tabId=2403&DCMP=MIXEDSIGNALANDANALOG+Other&HQS=Other+OT+radiation

    The National space products will soon be added to this page, but for now can be found at:

    http://www.national.com/en/space/index.html

  • 0 in reply to Kirby Kruckmeyer96848
    Prodigy 100 points

    Hi Kirby,

    Thanks for the pointers. I do have another question with regard to proper grounding of the ADC14155QML-SP. In our system it is planned to have seperate analog and digital ground planes. On page 4 of the data sheet it states that the DRGND pins should be connected to the system digital ground but in section 7.0 of the data sheet it recommends using a single common ground plane...which one is correct?

    In the past I have always treated ADCs/DACs as analog components and connected all ground pins (AGND and DGND) to the system analog ground plane and then used the differential data outputs to cross over the split ground; the theory being this prevented any noise from digital switching coupling into the analog circuitry of the ADC/DAC. However, in this case the ADC14155QML-SP has single-ended ouputs that I need to drive into an FPGA...what is the best way to handle this?

    Lastly, the SMD part number for this part is listed as TBD...any updates as to when it will have an SMD part number?

    Thanks again for the help,

    Steve Mitchell

  • 0 in reply to Stephen Mitchell
    TI__Genius 17125 points

    For the ADC14155QML, the analog and digital returns should be on the same ground plane as described in section 7 of the datasheet.  With the FPGA on a separate digital plane, a CMOS buffer should be used between the ADC outputs and the FPGA.

    Releasing the SMD for the ADC14155QML is waiting for DLA to update the wording of MIL-PRF-38535 and MIL-STD-883 to include the use of decoupling capacitors inside the package.  Work on this is in process.  We hope to have this completed before the end of the year.

     

  • 0 in reply to Kirby Kruckmeyer96848
    Prodigy 100 points

    Hi Kirby,

    A while back you had suggested using the THS4513 (or THS4511) amp to drive an ADC. Our ADC selection has changed to the TI ADS5463-SP. On page 17 of the ADS5463-SP data sheet an example circuit for using the THS4509 to drive the ADC is shown in figure 17.

    Can the THS4509 in figure 17 of the ADS5463-SP data sheet be replaced with the THS4513-SP with no changes to resistor/capacitor values? (assuming same gain is needed)

    In out application we will have a DC-coupled input to the THS4513 that is a 50ohm source. My understanding is that the 78.9ohm and 100ohm resistors on the input of the amp in figure 17 of the ADS5463-SP data sheet are there to match the impedance of the source..but 100||78.9 is only 44.1ohm so is my understanding wrong?

    Lastly, a very similar circuit drawing is show in figure 66 of the THS4513-SP data sheet for driving an ADC. However, the resistor values on the input of the amp are slightly different...69.8ohms show in THS4513-SP data sheet vs. 78.9ohm shown in ADS5463 data sheet....which value woudl be correct for using the THS4513-SP to drive the ADS5463-SP ADC?

    Any help you can provide for properly driving the ADS5463-SP with the THS4513-SP is greatly appreciated.

    Thanks,

    Steve