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THS4520 - ADC input driver(AC, DC) of ADS58C28

Other Parts Discussed in Thread: THS4520, ADS58C28, LMH6552, THS4509, THS4541, OPA2357

Hi all,

Would you mind if we ask THS4520?

Our customer will use ADS58C28, and our customer would like to measure followings signal;

<Sampling signal>
-Input voltage range: 0-5V
-Input type: rail to rail
-Power type: single suply 5V
-Signal rate: 20Mbps

When they use ADS58C28, TI recommends LMH6552, THS4509 and THS4520 as ADC input driver(AC ,DC both).
These amplifiers don't correspond input range 0-5V, do they?

So, how about OPA2357 and THS4541?
If you have some advice, could you let us know?

Kind regards,

Hirotaka Matsumoto

  • Hello Hirotaka-san,

    When you mention the input range of 0-5V, do you mean the input common-mode range of the amplifiers to be 0 to 5V? The fully differential amplifiers (FDA) LMH6552, THS4509, THS4520 and THS4541 do not have the input type as rail-to-rail or input common-mode range from 0 to 5V, but can be used to process 0 to 5V input signal swings. For example, the below THS4541 circuit is configured for a unity gain single to differential conversion, where you can process a 0 to 5V voltage range signal. 

    The OPA2357 is an op-amp with single-ended output, and thus would not recommend while driving the ADS58C28.

    One thing to remember is that the ADS58C28 has an input common mode voltage of 0.95V and 1.9Vpp full scale input swing. While processing a 0 to 5V input swing with the output common mode voltage of the FDA set to 0.95V, you are definitely going to clip on the lower output level side in a unity-gain FDA configuration. This is because each of FDA outputs has to swing 1.25V below the output common mode voltage of 0.95V, which is outside the output signal limits. In such a scenario, you would have to configure the gain of FDA lower than unity-gain to not clip at the FDA outputs. This should also take care of the full-scale clipping at the ADC. I would highly recommend using the THS4541 for your project, if the input voltage range is what I interpreted.

    Best Regards,

    Rohit

       

  • Rohit san

    Thank you for your excellent reply!

    "Do you mean the input common-mode range of the amplifiers to be 0 to 5V?" -> yes, we mean the input common-mode range of the amplifiers.
    And, we reccomend our customer to use THS4541.

    Kind regards,

    Hirotaka Matsumoto