AMC1311 Input resistance requirement

Part Number: AMC1311-Q1
Other Parts Discussed in Thread: AMC1301, AMC1300, AMC1311

Hi, is it necessary to use two resistances in each input path (ex- 39 ohm in the circuit) or we can just put one combined resistance in only path (ex- 78 ohm in Vinp path).

Also, is it not required to put a resistance (nearly same as the shunt resistance) in Vinn path for bias effect as in case of ac voltage sensing in AMC1300 or AMC1301?

over 1 year ago

+1 Tom Hendrick over 1 year ago

TI__Guru**** 175111 points

Hi RP,

Welcome to our e2e forum! The AMC1311 has a single-ended input. Its designed specifically for voltage monitoring. There is no VINn pin with this device and you do not need to worry about the bias currents associated with the AMC1300 or AMC1301. It is not clear in your schematic snippet above, but the bottom side of R22 (the junction of R22 and R26) needs to be referenced to GND1.

+1 RP over 1 year ago in reply to Tom Hendrick

Prodigy 30 points

Thanks for the reply.

Amc 1301/1300 part is clear.

i want to ask about R19 and R27, is it necessary to use both resistance or we can use only one resistance (R19=78 ohm)?

+1 Tom Hendrick over 1 year ago in reply to RP

TI__Guru**** 175111 points

As I mentioned before, the AMC1311 has a single ended input, R27 is not needed, but C19 has to be referred to GND1. The SHTDN pin also needs to be referred to GND1.

0 RP over 1 year ago in reply to Tom Hendrick

Prodigy 30 points

Just one more thing, for AC voltage monitoring using AMC 1300/1301, is it necessary to use Vref as we have to shift the negative part of the differential output..

0 Tom Hendrick over 1 year ago in reply to RP

TI__Guru**** 175111 points

Hi RP,

Yes - please have a look at this tech brief: https://www.ti.com/lit/an/sbaa229a/sbaa229a.pdf

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AMC1311 Input resistance requirement