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Looking for a replacement for the ADS7820

james marquardt
Prodigy 80 points
Other Parts Discussed in Thread: ADS8505, ADS8504

Hello,

I am looking for a replacement for the ADS7820 as it is not RoHS compliant and is no longer available.  Of course a drop in replacement would be great, but if I can get something close, I can deal with having to redo the PC Board.

Any recommendations are appreciated.

JIm

  • 0
    TI__Expert 5705 points

    Hi Jim,

    We don't have an exact drop-in replacement but the ADS8504 (12-bit) or ADS8505 (16-bit) are good alternatives. Both devices are pin-compatible with the ADS7820 and have similar performance, but the ADS850x devices are also faster (250KHz), lower power and (probably) cheaper. There are a few significant differences between the ADS7820 and the ADS850x:

    - The ADS7820 has a 5V unipolar input range while the ADS850x devices have a +/-10V range

    - The ADS7820 provides a straight binary output while the ADS850x devices output conversion data in 2's complement format

    - The ADS850x are only available in an SOIC package

    Using the ADS8504 will require a new input driver that can scale and offset the 0-5V ADC input to span the +/-10V range. Additionally, software modifications may be needed to convert the ADC output from 2's complement to straight binary format.

    On the other hand, with the ADS8505, you can use the existing input driver over just 1/4th of the ADC's full-scale input range, without losing resolution. And to convert the 16 bit 2's complement output to 12 bit straight binary words, all you have to do is capture the 12 MSBs of the output word and ignore the 4 LSBs.

    It appears that the ADS8505 would be the better (less disruptive) option.

    Thanks,
    Harsha