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ADS8339: Reference buffer

Roy Hsu
Genius 9190 points
Part Number: ADS8339
Other Parts Discussed in Thread: REF5045, THS4281, , REF3240, OPA140, ADS8864, REF6045, OPA350

Hi Team,

1. In the ADS8339 EVM, REF5045 is buffered by THS4281 then sent to the REF pin of ADS8339. I'm also aware that our REF6xxx family is internally buffered. What are the pros and cons of using the EVM architecture v.s. the REF6xxx?

2. Below is a snapshot from the TIDU181. The REF3240 below is shared between the REF pin of ADS8864 and the ADC driver OPA140. I'm wondering if this would affect the ADC operation or not.

Thanks.

Roy Hsu

  • 0
    TI__Genius 9190 points

    Adding the picture which is missing in my previous post.

  • 0 in reply to Roy Hsu
    TI__Mastermind 36240 points

    Hello Roy,

    The REF6045 would be the preferred reference for the ADS8339.  The external ref buffer was recommended in the datasheet because the REF60xx did not yet exist.  There are a couple of cases where you may want to use the REF5045 and an external buffer.

    1. You have multiple ADC's in the system, and you would like to use one system reference.  Each ADC would have its own external buffer, but all ADC's would use the same reference.

    2. The REF6045 drift is 5ppm/C max.  The REF5045 drift is 3ppmC max for the higher grade part.  You can get better performance using the higher grade version of REF5045 and the suggested external buffer circuit.

    Regarding the reference design, the OPA350 functions as the external buffer for the ADS8864, and will take care of driving the input capacitor charge currents.  The REF3240 will only see the high input impedance of the OPA350, and can be used in other parts of the system with no degradation in accuracy.

    Regards,
    Keith Nicholas
    Precision ADC Applications