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# AMC1211-Q1: AMC1211-Q1 Sensing Accuracy

Part Number: AMC1211-Q1

Hi Team,

There is customer want to know how to calculate the output voltage error when use AMC1211 in automotive.

Is gain error include input offset voltage error ?

When sensing the voltage, I need to know how accurate this solution can sense it. Which factor can affect the voltage sensing reliability?

1. Gain error with input resistance of AMC1211-Q1 (AMC1211-Q1 might have buffer on the input side with 1Gohm input resistance?)

2. Rf+Cf filter?

3. Input offset voltage of AMC1211-Q1

3. Modulator performance of AMC1211-Q1?

4. Gain error with Input impedance of TLV313-Q1 (But there is not gain error and input resistance value in TLV313-Q1 datasheet..)

5. Input offset voltage of TLV313-Q1

Should I consider all of these things? How can I suggest reasonable voltage sensing accuracy to my customer?

BR

Songzhen Guo

• Hi Songzhen,

Is gain error include input offset voltage error ?

No, think of the voltage transfer as being is the form of y=mx+b. m is the gain, and b is the offset. Gain error is the difference between the expected and actual gain.

When sensing the voltage, I need to know how accurate this solution can sense it. Which factor can affect the voltage sensing reliability?

All of them.

This excel calculator (look under the single ended configuration, then select AMC1211-Q1) accounts for 1, 3 & 3.

https://e2e.ti.com/support/amplifiers/f/14/p/815789/3019110#3019110

2. Will be an expected voltage drop across Rf which can be calculated and accounted for in the expected gain calculation. Make Rf as small as possible to minimize the voltage drop, increase Cf to maintain fc = ~200kHz.

4.The gain error of the TLV will be set by the tolerance mismatch of the gain and feedback resistors. i.e if Rfeedback = Rgain = 1k and they both have 1% tolerance, the worst case maximum gain error would be (1k*1.01)/(1k*.99) = 1.02, where 1 is expected. The worst case minimum gain error would be the inverse, (1k*1.01)/(1k*.99) = 0.98, where 1 is expected.

5. Input offset voltage of the TLV will be directly translated to the output, i.e, take the end result input offset voltage for the AMC1211 calculation and add the TLV offset error.

Please take a look at these calculations and let me know if you have any questions.