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Original question:

THS4151: Filter component selection guidance

AMC1300B-Q1: SPWM Measurement using AMC1300B

Rajasekaran
Intellectual 945 points
Part Number: AMC1300B-Q1
Other Parts Discussed in Thread: AMC1300, THS4131,

Dear sir,

We are using AMC1300 based voltage and current measurement circuit. Please find the attached schematic and output waveforms. 

Schematic. 

The output waveform is 

Channel 1 & 3 are gate pulses. 

Channel 2 - Output waveform measured using above circuit 

Channel 4 - Output voltage measured using isolated voltage measurement device (different product)

As shown in the parent thread ([Resolved] THS4151: Filter component selection guidance - Amplifiers forum - Amplifiers - TI E2E support forums), we can able to measure the output pulses for the DC circuits. 


If we use the same measurement circuit in the inverter, we are unable to get the output voltage. Please find the above measured waveform from the inverter output (Channel 2). The Inverter switching frequency 5-20kHz. We can able to get the DC pulse output for the same schematic. But it doesnt work for the AC output (SPWM). 

Kindly guide us to solve the issue. 

Thanking you.

Thanks & Regards,

Rajasekaran.

  • 0
    TI__Mastermind 47625 points

    Hi Rajasekaran,

    How are your power-supplies generated? Are you using +/-1V bipolar power supplies for the high side of the device? 

    Where are the output waveforms measured? Differentially at the output of the AMC or at the output of the THS?

  • 0 in reply to Alexander Smith
    Intellectual 945 points

    Dear sir,

    We are using isolated power supply for AMC high side and low side. Two different 5V isolated power supplies. The THS4131 amplifier having +/-12V power supply. 

    The output waveforms are measured at the output of THS4131.

    Thanks & regards,

    Rajasekaran.

  • 0
    Guru 140200 points

    Hi Rajasekaran,

    some of the issues discussed in the following post seem to be valid here as well:

    Kai

  • 0 in reply to kai klaas69
    Intellectual 945 points

    Dear sir,

    We implemented the AMC1300 for voltage measurement and we are unable to change the circuit now. 

    Queries:

    1. AMC1300 output are connected to an amplifier THS4131. Cloud you please guide us to terminate the AMC1300 output symmetrically. 

    2. In the above circuit, does THS4131 will generate the differential output or floating differential output. If it generates floating differential output, Cloud you please help us to convert it as fully differential output.

    Thanking you.

    Thanks & Regards,

    Rajasekaran.

  • 0 in reply to Rajasekaran
    TI__Mastermind 47625 points

    Hi Rajasekaran,

    It looks like some of the switching noise may be coupling into the measurement. Please take additional scope captures at the input and output of the AMC1300B-Q1. Additionally, please take scope captures of the power-supplies. 

    As Kai mentioned, due to using a device with low input impedance in combination with a large sensing resistor, I would expect to see some offset and potentially gain error with the measurement. However, the main issue seems to be the switching noise. 

    I am not an expert on the THS4131 so I've moved your additional thread with specific questions in regards to that device to their forum.