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DRV8243H-Q1EVM: Current accuracy

Sergej EgorenkovSergej
Prodigy 20 points
Part Number: DRV8243H-Q1EVM
Other Parts Discussed in Thread: DRV8243S-Q1LEVM, DRV8243-Q1, DRV8873-Q1

Hello,

I've recently tested the "DRV8243S-Q1LEVM" evaluation board. An important point for me was the current measurement accuracy.

I got better current measurement accuracy than what is in the datasheet.

So I wanted to ask you why is that?

According to the data sheet, it comes with:

 

I did my measurements as follows:

I have set the following settings on the GUI: S_ITRIP: 2.64V RIPROPI: 1.5kΩ Slew Rate: 43V/usec TOFF: 30 usec

I soldered the RIPROPI resistor 1.2 kΩ.

As a load I used resistive load. I examined the current measurement accuracy as follows:

- Measured the voltage at the IPROPI pin (mean value recorded on the scope - UIPROPI in tabel)

- Measured the current through the load with an ammeter (KEYSIGHT34450A)

- IIPROPI calculated according to the formula from the data sheet

- AIPROPI = 3075, RIPROPI = 1.2kΩ

- Compare the calculated IIPROPI current with the measured current (with KEYSIGHT34450A).

- From this the measurement accuracy is determined

Here are my values:

What's the difference? Can you please tell me what the current measurement accuracy depends on and why it is so inaccurate with smaller currents?

My desired current measurement range is up to 6 A.

Thanks and Regards

Sergej

  • 0
    TI__Mastermind 24615 points

    Hi Sergej,

    Thank you for your question and sharing your data.

    Based on your measurement result, accuracy is getting lower in <0.8A and <0.2A.  This is matching to datasheet. 

    Datasheet min/max includes the parts to parts variation. So one part you measured could show better.

    In order to keep better current sense accuracy in high current region, DRV8243-Q1 current sense accuracy in low current region is compromised. This is the reason.

    If you are looking for better current accuracy in lower current area, DRV8873-Q1 could be option.

     

    regards

    Shinya Morita

  • 0 in reply to Shinya Morita
    Prodigy 20 points

    Hi Shinya,

    Thank you for the feedback.

    I.e. I got a good component that has better measurement accuracy, but it could also be something else?
    I was also able to get a component with poorer measurement accuracy?

    What does it depend on?

    Does it depend on the batch?

    I made measurements at +75 °C and -25 °C. I could not determine any dependency on the ambient temperature. The results were similar.

    For me the range 0.2 A - 0.8 A is important. I need better accuracy here. Is there any way to improve accuracy in this area?


    The DRV8873-Q1 has worse accuracy (other than what you've attached) according to the datasheet:
    on page 7:


    Thanks and Regards

    Sergej

  • 0 in reply to Sergej EgorenkovSergej
    TI__Mastermind 24615 points

    Hi Sergej,

    Thank you for your question.

    Accuracy has parts to parts variation. Particular single part could be much better than SPEC min/max.

    Datasheet shows data of 6 sigma.as follows. Finally datasheet min/max is device performance for all part we ship out.

    regards

    Shinya Morita

  • 0
    Prodigy 20 points

    Hello Shinya,

    Thanks very much.

    Can you influence the accuracy (e.g. through settings or external components)?

    You are offered the DRB8873-Q1 because it has better accuracy.
    I looked at the datasheet of the driver but the accuracy doesn't match your attachment (see my answer from before).
    Is that a different component?
    Could you please send me the designation?

    Thanks and regardes

    Serej

  • 0 in reply to Sergej EgorenkovSergej
    TI__Mastermind 24615 points

    Hi Sergej,

    Accuracy variation comes from part to part variation. External component and settings does not help.

    My previous attachment of DRV8873-Q1 is extracted from datasheet. It is at page 7.

    Here is the link of product folder. Then datasheet is here.

    DRV8873-Q1 data sheet, product information and support | TI.com

    regards

    Shinya Morita