ISO224: ISO224 use with ADS8586S ADC

Hi Mehmet,

yes, you can do this.

Kai

Thank you. What about the configuration without opamp? if I connect ISO224 output directly to ADS8586S ADC, can ISO224 output drive ADS8586 ? Which datasheet parameters should I consider?

Regards,

Mehmet.

Hi Mehmet,

the differential output of ISO224 is needed to provide a high common mode rejection from high side to low side and to guarantee a high noise immunity. It's not wise to use only one of the output signals of ISO224 and to omit the differential amplifier (or the true differential input stage). I would never do this.

Kai

Hi Kai,

Thanks for your answer. Actually I want to use both positive and negative output OUTP and OUTN and connect them to differential ADC like below, I take it from datasheet. There is only R-C-R network and connected to differential ADC directly, without using extra opamps. I am asking to be sure, below circuit is not a good idea without opamps at the output side of ISO224? 

Thanks,

Mehmet

Hi Kai,

Thanks again, I am clear now. One final question about R-C-R filter at the output of ISO224, do you have any suggestion about values of capacitor and resistor?

(Input Mains 50hz)

Best Regards,

Mehmet.

Happy Easter, Mehmet!

the RCR filter is more a charge kick back filter than a standard low pass filter. The dimensioning of this filter mainly depends on the used ADC. The datahseet of ADS7945 discusses this issue very thoroughly in section "Application Information" on pages 33, 34 and 35.

The ADS8586S, on the other hand, does not need such a charge kick back filter because it contains its own ADC driver.

Kai

Happy Easter to you too, Collin :-)

Kai