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Help Selecting Level Shifting Amplifier

Rajasekaran
Intellectual 945 points
Part Number: AMC1300
Other Parts Discussed in Thread: OPA172, TLV271, ADS131A02

Dear sir,

we are using AMC1300 for current measurement. 

Measurement range : 0 to 75A

Shunt resistance : 1mOhm

High side voltage : 75mV

low side voltage : 615mV.

measurement signal frequency : DC-20kHz

We wish to have amplifier get the secondary side voltage as 10V. Could you please suggest the suitable amplifier to connect in the AMC1300 output circuit. 

Thanks & regards,

Rajasekaran

  • 0
    TI__Mastermind 47625 points

    Hi Rajasekaran,

    I'm going to move this to the amplifiers forum so that they can help you select an amplifier. 

    Would you like to perform a differential to single-ended conversion as well? 

    Have you already selected an ADC? If so, which one? 

  • 0 in reply to Alexander Smith
    TI__Guru*** 140136 points

    Hello Rajasekaran,

    I will help you with an amplifier. I understand that sense voltage is 0mV to 75mV, AMC1330 converts that to 0mV to 615mV differential. The (yet to be determined) amplifier should convert AMC1300 output to 0V to 10V scale (Gain 16.26) abs min BW=16.26*20kHz = 325kHz. abs min slew rate = Vpp*pi*F = 0.63V/us. Starting look at least 4 times the abs minimum. 

    The 10V is easy, the 0V is more difficult if the op amp power is "single supply". Amplifiers can get very close to 0V output, however this is also the low current range near 0 Amps of input current where measurement error can request a output of less than 0V which slows the amplifier response due to a effect called "overload recovery". Having an output range instead of say, 0.5V to 10V would be better. Other solutions are to use a +/- power source to the op amp or simply tolerate slower response near 0A where it might not matter.

    Lots of amplifiers could work, like TLV271 or higher performance OPA172, Supply voltage 11V to 16V for TLV271, 11V to 36V for OPA172.

  • 0 in reply to Ron Michallick
    Intellectual 945 points

    Dear sir,

    Thanks for your reply. 

    The AMC1300 may get the input from AC signal. so we will get the AMC1300 output as +/-615mV.

    we are looking for the differential amplifier. Could you please suggest some models for the same.

    Thanks & regards,

    Rajasekaran.

  • 0 in reply to Alexander Smith
    Intellectual 945 points

    Dear sir,

    Thanks for your reply. 

    we would like to amplify the signal as differential signal. and we need to identify the ADC also. Kindly suggest the suitable ADC having 24-bit resolution and minimum 50kS/s per channel for this signal. 

    Thanking you.

    Thanks & regards,

    Rajasekaran

  • 0 in reply to Rajasekaran
    TI__Guru*** 140136 points

    Rajasekaran,

    Attached in a lightly tested in simulation circuit that takes -75mV to 75mV sense voltage and converts that to +/-10V difference output and that goes to an ADC, ADS131A02 , with a 3.3V supply, charge pump off, and Vref set to 2.442V. The HV and ADC common mode voltage is 1/2 of the 15V and 3.3V supply. 

    Full scale for the ADC is set to 120% of the 75mV signal. If desired, It can set to 100% instead by removing R12 and R11 and re-scaling the simple resistor divider to get a gain of 0.241

    Draft1.TSC

  • 0 in reply to Ron Michallick
    Intellectual 945 points

    Dear sir,

    Thanks for your help. 

    we will build the circuit based on the reference circuit. 

    Thanks & Regards,

    Rajasekaran