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DRV2510-Q1: Is there any methods to improve the performance because of tolerance of components when differential mode be used

YUN LIN
Intellectual 535 points
Part Number: DRV2510-Q1

Hi teams,

 As you know, there is differential mode can be used for DRV2510. And low pass filter consisted of resistors and condensers is recommended for each IN port.

However, because of tolerance of resistor or condenser, these two LPF would show characteristic variation between each other.

 For example,  if the resistors of  +/- 5% be used for the LPFs, and the resistors of LPF to IN+ are all +5% while the resistors of LPF to IN- are all -5%, the difference between IN+ and IN- could be more than 10%. In this case, even if two same PWM signals which had the same peak voltage and duty ratio were introduced to IN+ and IN-, because of the difference that would be amplified according with GAIN value of IC, the difference of voltage will be generated in the output side. 

  Above all, we wonder there is any method that can help us to decrease the difference when differential mode be used.

Best regards,

Yun Lin.

  • 0
    TI__Guru* 84915 points

    Hi, Yun,

    Unfortunately, these are components issues based on their worst cases tolerances. So, the only recommendation for this kind of issues is to try to get components with less percentage of tolerance. In case your application is really sensitive to these values, I also recommend to ensure that the PCB traces have the same width and length. This will help to prevent additional differences on the differential inputs.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Intellectual 535 points

    Hi Luis,

     Additionly,  there is description on the BD Mode Modulation as below figure5 from datasheet.

    The waveforms of OUT OUTP and OUTN only be shown in the graph.

    Could you show the input waveform introduced into the IN+ and IN- port at the same time for the figure5.

    Best regards,

    Yun Lin.

  • 0 in reply to YUN LIN
    TI__Guru* 84915 points

    Hi, Yun,

    Unfortunately, I don't have the full details about the input voltage used in these graphs. However, I can ensure that for each case it was used a constant level.

    - 0V differential input for first graph
    - Positive differential input for second graph. 
    - Negative differential input for third graph

    Depending of the selected gain, the differential input can be increased until the output voltage reaches the PVDD level.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Intellectual 535 points

    Hi Luis,

     In our opinion, the 1st case of "0V differential input" cannot be achieved becasue of the tolerance of conponents of IN side.Therefore, ouput side can not be stopped because of differential inputs signal. Is that right? Additionly, for our usage of the DRV2510 device, there is a microcontroller sending two independent PWM signals to IN+/- through the low pass filters.I mean do you have any more suggestions that can help to upper the performance.For example, whether utilizing a DA converter between microcontroller and haptics driver IC that can get a higher performance than the current method that using a microcontroller directly or not.

     There are parameters of "VICMIN" and"VICMAX" in table6.5(Electrial Characteristics) , could you help to provide more information about what these two parameters are. We thought these are the limitaion of the differential voltage between IN+ and IN-.

    Best regards,

    Yun Lin.

     

  • 0 in reply to YUN LIN
    TI__Guru* 84915 points

    Hi, Yun,

    The 1st case is not related to the input components. The device has a 3V input common-mode level generated internally if the AC-coupling capacitors are used (recommended connection). The capacitance tolerances won't affect the common-mode level in the device. So, when there's a 0V differential input (both inputs at same level) the device will take it as the reference level.

    What I would recommend is to request a DRV2510-Q1EVM so you can perform these tests and ensure that this is correct. You should expect this behavior even if the component tolerances are 10%.

    The VICMIN and VICMAX are the limits of the common-mode level when the internal bias is not used (no AC-coupling capacitors). In case you are looking to use a different common-mode level (differential input with an offset level), these would be the limits for the device.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Intellectual 535 points

    Hi Luis,

    From the user guide of DRV2510-Q1EVM, there is Figure4 of recommended input low pass filter as below. 

    It seems there is not any AC coupling capacitor in it.

    https://www.tij.co.jp/jp/lit/ug/slou449/slou449.pdf?ts=1607953859110&ref_url=https%253A%252F%252Fwww.tij.co.jp%252Ftool%252Fjp%252FDRV2510Q1EVM 

     As your mentioned, the VICMIN and VICMAX are the limits in our use case. Are these limits the difference between IN+ and IN-, or the value for each side.

    Best regards.

    Yun Lin.

  • 0 in reply to YUN LIN
    TI__Guru* 84915 points

    Hi, Yun,

    This is correct. As shown in the DRV2510-Q1EVM, it is possible to use the analog inputs without AC-coupling capacitor. This is a case where you may use external common-mode level.

    In the typical application circuits of the datasheet, you may find the AC-coupling capacitors suggested between the LPF and the inputs. This configuration allows using the internal common-mode level.

    Regarding your question about the common-mode level limits, these limits are the value for each side.

    Best regards,
    Luis Fernando Rodríguez S.