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DRV8662: Need more explanation about Single-Ended Input with Dummy Filter

Part Number: DRV8662

Hi team,

I would like to understand better why dummy filter is needed for single-ended input.

I mean, I want supplemental explanation about P.13,14 of SLOU319B.

Could you support this?

And, I am not sure the difference between Figure 12 and Figure 13 of SLOU319B. First of all, what do red, yellow, orange waveform mean?

Regards,

Noriyuki Takahashi

  • Hi Takahashi-san,

    Let me explain further the dummy filter effect:
    The reason to use a dummy filter is the difference in settle time between single-ended input and differential input.

    • With differential input, both IN+ and IN- settle at the same time, thus the output signal looks stable all the time.
    • With single-ended input, IN+ and IN- does not settle at the same time, so the output will have some variation during this settle time. The settle time begins at the moment the device is enabled (through EN pin).

    On Figure 12 and 13 you can see the following:

    • Yellow is OUT+
    • Red is OUT-
    • Orange is differential output, it is the math function of (OUT+) - (OUT-)


    Finally, by using the dummy filter and connecting the input of the filter to a resistor divider from EN pin voltage, the variation at the output can be reduced, this is because the resistor divider provides the mid-supply bias that the single-ended input already has. This effect can be observed on Figure 15.

    I hope this helps, please let us know if you have further questions.

    Best regards,
    -Ivan Salazar