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DRV8301-69M-KIT Analog interface

Mojo
Expert 1570 points

Other Parts Discussed in Thread: DRV8301

Hi Chris,

with respect to the DRV8301-69M-KIT, I'll be grateful if you could specify the bandwidth of the analog filters for the sampled waveforms:

1. phase currents

2. phase voltages

3. DC-Bus voltage

I'm sorry but I haven't got the knowledge to understand these circuits...yet...

thanks a lot

  • 0
    TI__Mastermind 21320 points

    Hi Mojo,

    I will jump in for Chris here and see if I can't answer some of your questions. As you have noticed the controller reads a variety of values from the board. I may need some clarrification on exactly what you are looking for but I will give you a brief rundown for now.

    1. The kit senses phases currents through a sense resistor on the low side of each half bridge (R80, R81, R82). The high side and low side of this sense resistor feedback to a differential amplifier. The kit makes use of both the internal amplifiers on the DRV8301 and external amplifiers. The amplfier feeds to an ADC on the controller. If you have more questions about these circuits I can go into furthur detail.

    2/3. The phase voltages and DC-Bus voltage are sensed through voltage dividers with a capacitor on the low side to filter out some of the noise (R60, R62, C67, etc...). These dividers can be adjusted if your application runs at a lower voltage to obtain a better accuracy.

    Here is the schematic I am refering to. Feel free to ask more questions if you need more explanation or I have completely missed the mark.

    7180.515502~1.PDF

  • 0 in reply to Nicholas Oborny
    Expert 1570 points

    Hi Nicholas,

    thanks for the reply.

    actually I'm only interested on the value of the bandwidth of the low pass filters of the various signals (currents and voltages) that are currently implemented on the TI kit.

    when I come to design my own board, I'll use the appropriate values..

    So if you can provide a small table with the various bandwidths of the analog filters that will be great

    thanks a lot

    keep on the great support !!

  • 0 in reply to Mojo
    TI__Mastermind 21320 points

    Mojo,

    On the F2806XISO-CONTROLCARD there are low pass filters on each of the ADC pins A0-7, B0-3. This is to filter out some high freqeuncy noise.

    R = 56 Ohm in series and C = 2.2 nF to GND. I'm not sure how much you know about filters but a quick google search on low pass filters should answer any basic questions.

    To calculate the cutoff frequency the formula is "Fcutoff = 1/(2*pi*R*C)". So for the control card 1/(2*pi*56*2.2E-9) = 1.29MHz