TLV6001: Back calculating the input from output signal chain with Isolated Amplifier and opamp

HARI T O1

Part Number: TLV6001
Other Parts Discussed in Thread: AMC1350

Hi Team,

We are measuring the voltage of a charger using the below circuit with the help of an ADC present in a uC.

The value of charger voltage is required for some other applications.(he value of charger voltage is used to calculate isolation resistance).

So I tried to calculate the input from output. I am getting an error of almost 2V in my calculations.

We are using AMC1350 and TLV6001 in the signal chain.

Please see my circuit diagram and calculations below.

From the circuit diagram you can see that the input V2 is 58V.I used the equation shown in the second image to calculate V2 from Vout.

I am getting a value of 56V instead of 58V.May I know where I went wrong.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 318050 points

Is the current through R4 and R7 the same, and through R5 and R8?

0 HARI T O1 over 2 years ago in reply to Clemens Ladisch

Expert 1675 points

Current through each resistors is given below,

R4,R5 = 124uA

R7,R8 = 32.15uA

0 Clemens Ladisch over 2 years ago in reply to HARI T O1

Guru 318050 points

Sorry, my question did not make much sense.

0 Ashley Kang over 2 years ago in reply to Clemens Ladisch

TI__Genius 16240 points

Hi Hari,

I confirmed you did the derivation for the first portion using the TLV6001 correct in Section 1. See below for the transfer function and simplification similar to what you did.

Since the AMC1350 is not an op amp device, I will move this thread over to the data converters team to assist further.

Best Regards,
Ashley

0 HARI T O1 over 2 years ago in reply to Ashley Kang

Expert 1675 points

Hi Ashley,

Thank you very much.

Regards

HARI

0 Alexander Smith over 2 years ago in reply to HARI T O1

TI__Guru 55542 points

Hi Hari,

You can reference our voltage sensing accuracy excel calculator for this: https://www.ti.com/lit/zip/sbar013

However, I see that you are powering both VDD1 and VDD2 from the same power supply in your schematic?

This connection violates the isolation barrier and separate power supplies and grounds are required for correct use of the device.

0 HARI T O1 over 2 years ago in reply to Alexander Smith

Expert 1675 points

Hi Alex,

Thank you very much.

In original board the VDD1 and VDD2 are different.

While back calculating I am not getting the exact value.There is a 2V difference.

I am not considering the common mode voltage of AMC1350(1.44V) in my calculation.

Will it cause any error in back calculation.

Regards

HARI

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TLV6001: Back calculating the input from output signal chain with Isolated Amplifier and opamp