AMC1301: How to choose divider resistor for AMC1301 and AMC1200

Lin_Charles

Part Number: AMC1301
Other Parts Discussed in Thread: AMC1200

Hi team,

My customer is using AMC1200/AMC1301 to measure 5V bus. The divider resistor is 120k/2.4k. And 1200 works fine but 1301 may have some deviation. When changing resistors to 800/20, the result is good for 1301. My questions are below,

I believe this deviation is from Ib of 1301, right?
Do we have any recommendation about the selection of divider resistor for 1200 and 1301?
What causes 1200 and 1301 cannot be P2P?

Thank you for your help here.

over 6 years ago

0 kai klaas69 over 6 years ago

Guru 140200 points

Hi Lin,

have you seen section 10.2.2 of datasheet of AMC1301?

Kai

0 Lin_Charles over 6 years ago

TI__Expert 4260 points

YES. But you means that 120k/2.4k and 120/2.4 will have the same result? Only need to add R3' on the input pin of VINN?

0 Tom Hendrick over 6 years ago in reply to Lin_Charles

TI__Guru**** 176421 points

Hi Charles,

Picking the resistive divider boils down to choosing values that get your voltage into the input range of the amplifier, the amount of power you are willing to dissipate, and the levels of offset and gain that you can tolerate. The bias current in the AMC1301 will have offset and gain issues with larger values resistors acting as the 'shunt'. A larger value resistor (2.4K vs. 20 ohms) makes a difference due to the bias current.

Technically, the AMC1200 and AMC1301 are pin compatible, the difference is in the input section of the amplifier as can be seen in the two block diagrams - the AMC1200 does not have the VCM block and does not have the same resistive elements on the input stage.

0 kai klaas69 over 6 years ago in reply to Lin_Charles

Guru 140200 points

Hi Lin,

do both, keep the resistances of voltage divider as small as possible and add the compensation resistor.

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AMC1301: How to choose divider resistor for AMC1301 and AMC1200