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AMC1351-Q1: Design around the Differential to Single-ended Conversion OpAmp

k.m
Prodigy 10 points
Part Number: AMC1351-Q1
Other Parts Discussed in Thread: TLV313-Q1

Tool/software:

I am designing a circuit to detect voltage with a detection range of 800V through isolation using the AMC1351-Q1.

I am considering the circuit constants using the "IsolatedAmplifierVoltageSensingExcelCalculatorRevC.xlsx". Could you please provide guidance on the design around the Differential to Single-ended Conversion OpAmp?

Assuming the use of TLV313-Q1 as per the reference circuit diagram 8-3 in the AMC1351-Q1 datasheet, should I input the values of OPA Input Offset and OPA Offset Drift from the TLV313-Q1 datasheet, which are 0.75mV and 2.00 µV/°C?

I would like to know the design method for the reference voltage.

The calculated Reference Input Offset Voltage from the calculation sheet is 13.25mV. Should I determine the reference voltage divider resistors R3 and R4 to achieve 13.25mV?

Additionally, if you have recommended components for the Ref power supply op-amp and the Differential to Single-ended Conversion OpAmp, please let me know. Is it okay to use TLV313-Q1 for both?

  • 0
    TI__Expert 8455 points

    Hello,

    Thank you for your questions. Yes, you can use the TLV313-Q1 datasheet parameters for the differential to single-ended conversion section of the calculator if that is the op-amp you intend to use for the conversion. 

    The reference input offset voltage is calculated using the OPA input offset and OPA Rf/Rg tolerance user inputs. Rf and Rg should be sized to set the gain of the differential to single-ended conversion. 

    R3 and R4 should be sized to divide the voltage to a midpoint from the power supply to prevent common-mode shifting. The two op-amps depicted are the same they are just different channels. These topics are also discussed in this application note which may be helpful: Isolated Current-Sensing Circuit with +/-250-mV Input Range and Single-Ended Output Voltage. 

    Best regards,

    Eva