ISO224: Maximum Input Resistance

Ray Vincent Aranzaso

Genius 16535 points

Part Number: ISO224

Hi,

Good Day.

I just want to clarify why there is no value for the maximum input resistance of the ISO224.

It is because the ideal input resistance of an op-amp is infinite?

Please advise. Thank you very much.

Best Regards,

Ray Vincent

over 1 year ago

0 kai klaas69 over 1 year ago

Guru 140200 points

Hi Ray,

Ray Vincent Aranzaso said:
It is because the ideal input resistance of an op-amp is infinite?

No, this is not the reason. Usually, it is the minimum input resistance which can become an issue, since the input resistance forms a voltage divider in combination with the source resistance of the circuit driving the input of ISO224. To find out the worst case error caused by this voltage division, the minimum input resistance needs to be known. And since each min and max specification in the datasheet makes a costly and time consuming factory check necessary, the number of these specifications is limited to absolute necessary.

I guess that the max specification of input resistance is about 25...30% above the typical value.

Kai

0 Alexander Smith over 1 year ago in reply to kai klaas69

TI__Guru 51572 points

Please see this FAQ: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1023946/faq-does-ti-provide-guidance-on-input-resistance-variation-due-to-manufacturing-process-temperature-drift-and-lifetime-for-isolated-converters

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ISO224: Maximum Input Resistance