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Original question:

DRV8316: DRV8316 Ioffset_Current sense offset low side current in of CSA

DRV8316: DRV8316 Current Amplifier

Chuang Qi
Prodigy 10 points
Part Number: DRV8316

Tool/software:

Hello ,
DRV8316 datasheet states that SOA,SOB,SOC pin integrate current sense amplifier .What is the output impedance and output current of the SOX pin? ADC input range is 1V,and Is it possible to add external voltage divider resistors to adapt the voltage input range of the ADC?
Is there a more detailed internal block diagram of the I/V converter?

  • 0
    TI__Genius 16776 points

    Hey Chuang,

    Thank you for the question. We will take a look at this and provide feedback shortly.

    Best,

    Akshay

  • 0
    TI__Intellectual 2670 points

    Hi Chuang,

    I am looking into the requested information and aim to provide a more thorough response by next week. In the meantime, could you provide additional information on requirements for your system, such as what levels you are looking for from the output impedance and current and how they affect your system?

    Please refer to the following diagram of the output voltage as a function of the sensed current. The output range is based on VREF, but you can use a voltage divider from SOx to fit the output into the range of the ADC. We also typically recommend putting an RC lowpass filter on SOx to mitigate high frequency noise.

    Best,

    Davis

  • 0 in reply to Davis Jackson
    Prodigy 10 points

    Hi Davis,

    ADC input impedance 3000 ohms, refer to Xilinx UG580 Page 37, XADC input impedance.

  • 0 in reply to Chuang Qi
    TI__Intellectual 2670 points

    Hi Chuang,

    You will need to factor in this ADC input impedance when calculating the voltage divider and RC filter from SOx. I am still looking into additional information and will provide a response next week.

    Best,

    Davis

  • 0 in reply to Chuang Qi
    TI__Intellectual 2670 points

    Hi Chuang,

    We recommend designing the resistor divider to reduce the SOx output into the range of the ADC such that the max current (Vsox/Rtotal) is around 100uA. Then, you can filter the signal after this divider. To correct my earlier statement, the impedance shown in the table above should be used for the filter calculation, not the resistive divider. I hope this answers your questions.

    Best,

    Davis

  • 0 in reply to Davis Jackson
    Prodigy 10 points

    Hi Davis,

    Can you confirm whether the following resistor divider network can be used?

  • +1 in reply to Chuang Qi
    TI__Intellectual 2670 points

    Hi Chuang,

    Using Vsox/Rtotal, the resistor divider should only draw 100uA DC. As for the filter, we usually recommend setting the cutoff frequency to be 10x the switching frequency for trapezoidal control (100x for FOC). Based on the 3k resistor and 3p capacitor, I would recommend adding some additional capacitance to meet these recommendations. You can refer to section 9.2.1.1.6 of the datasheet for more information on SOx recommendations.

    Best,

    Davis