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INA240: Delta-sigma modulator for INA240

Dmitry Sharihin
Intellectual 420 points

Part Number: INA240
Other Parts Discussed in Thread: ADS1202

Hi there,

[For educational purposes] I want to implement current sensing in my low-voltage H-bridge circuit. Input voltage will not exceed 48V, and (at the moment) no isolation is required.

It seems that INA240 is good part to start with, however, 12-bit ADC integrated in TMS320F280049M looks like to be too coarse for optimal current loop control, so I'd like to use SDFM module, found in newer Piccolo devices.

Can I connect differential output of INA240 to the AMC1306 (or any similar delta-sigma modulator) to achieve 14-16bit resolution of current sensing?

Is there any non-isolated delta-sigma modulators which are easy to use as AMC130x?

Thanks

  • 0
    TI__Mastermind 32395 points
    Hello Dmitry,

    Are you planning to use the INA240 in an in-line configuration and thus measure bi-directional current? Or would this devices go on the high-side of the H-bridge? If you are measuring bi-directional current then it is fine to connect the differential output of the INA240 to the AMC1306 or whatever ADC is chosen. This would mean connecting VREF (1.8V) to the ADC_input- and Vout to ADC_input+. Here is a TI design measuring in-line current with the INA240:
    www.ti.com/.../TIDA-00913

    I don't think you will need any more than 14 bits of resolution since at 3.3V supply and 14 bits, LSB = 201uV. The INA240 has 40nV/rtHz input-referred noise and 400kHz -3dB bandwidth, which means its output noise will be:

    Vout_noise_rms = gain*sqrt(noise BW)*40nV/rtHz
    Vout_noise_rms = 20V/V * sqrt(400,000*1.57)*40nV/rtHz
    Vout_noise_rms = 634uV rms for INA240A1

    It looks like the ADS1202 could be a non-isolated substitute for the AMC130x.

    Hope this helps,

    Sincerely,
    Peter Iliya
    Current Sensor Applications
  • 0 in reply to Peter Iliya
    Intellectual 420 points

    Hello Peter,

    Yes, I'm planning to use INA240 in inline configuration. And ADS1202 looks like a good choice for measure its output.

    Thanks for your consideration