AMC1200: Minimum input current

Takuya Terada

Expert 5925 points

Part Number: AMC1200

Hi team,

My customer has a question about AM1200.

They would like to use under 15uA input current.

I found following fig on datasheet and i think 15uA is enough.

Could you tell me are there minimum input current?

best regarsd,
Takuya

over 5 years ago

0 Alexander Smith over 5 years ago

TI__Guru 58252 points

Hello Terada-san,

Can you please clarify what you are asking about?

Is the 15uA current flowing through the sense resistor, or are you asking if 15uA of current flowing into the device pin is acceptable?

If 15uA is flowing through the sense resistor and the full-scale range of 250mV is used, that means that the sense resistor will be ~16.66kohm. This sense resistor value will be in parallel with the differential input impedance of the AMC1200, which is 12kohm. This will generate large errors if this is the case.

For the second case, 15uA should be fine. There is not a specified minimum input current.

0 Takuya Terada over 5 years ago in reply to Alexander Smith

TI__Expert 5925 points

Hi Alex,

Thank you for your support.

Second case is what I meant.

>>This sense resistor value will be in parallel with the differential input impedance of the AMC1200, which is 12kohm. This will generate large errors if this is the case.

i dont understand why this generate large error.

could you explain about that?

best regards,

Takuya

0 kai klaas69 over 5 years ago in reply to Takuya Terada

Guru 140200 points

Hi Takuya,

if you mount a resistor of 16.66k and internally is a 12k resistor invisibly sitting in parallel, then the effective resistance is 6.976k, allthough you think it is 16.66k. This will generate a large error in your calculations.

Kai

0 Alexander Smith over 5 years ago in reply to kai klaas69

TI__Guru 58252 points

Hi Takuya-san,

For more information on this error, please consult this cookbook circuit: https://www.ti.com/lit/an/sbaa350/sbaa350.pdf?ts=1594655683176&ref_url=https%253A%252F%252Fwww.google.com%252F

Thank you Kai!

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AMC1200: Minimum input current