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DRV632: frequency response at low frequency

國元 羅
Prodigy 10 points

Part Number: DRV632

Hi team,

In current, I had a question with DRV632.

our schematic is below.

for audio frequency response of RMS value test

My test result(use 1k sine wave as 0dB reference)

20Hz->-2dB

1kHz->0dB

20kHz->-0.09dB

I need to adjust 20Hz result in +-0.3dB.

I try other combination but not better than this option

Can you give me some hint how to adjust resistance/capacitance value to fix this problem?

  • 0
    TI__Mastermind 18545 points

    Hello, 

    Our team is looking into this thread and will respond as soon as possible. 

    Best Regards, 
    Justin Beigel

  • 0
    TI__Guru** 114535 points

    Hi,

    Have you tried without RC filter at the output? Based on the schematic values there should not be an attenuation at 20kHz.
    Have you verified the attenuation is not present at the input of the DRV632?

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators

  • 0 in reply to Ivan Salazar
    Prodigy 10 points

    Hi teams,

    I change resistance value as figure below.
    Then,I did three experiments and the results are as follows

    1.no low pass
    (R202/R210->short,C170/C178->NC)
    20->-1.73dB
    1k->-0.001dB
    20k->-0.164dB

    2.change source to APx555 495mVrms
    (Use APx555 generate 495mVrms sine tone to ADAC_AOR and ADAC_AOL)
    20->-1.375dB
    1k->-0.001dB (497.7mV)
    20k->0.007dB

    3.bypass line driver(DRV632)
    (R204/R202->NC,connect C169 to AOR net/ R211/R210->NC,connect C175 to AOL net)
    (verified original source)
    20->-0.129dB
    1k->-0.001dB (497.7mV)
    20k->0.043dB

  • 0 in reply to 國元 羅
    TI__Guru** 114535 points

    Hi,

    Did you removed the low-pass filter for the 2nd test as well? I would say results from test 2 are looking OK.
    I couldn't open the picture most likely due to protected, network, I'll check if from a different place.
    Let us know if you have any further questions.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators

  • 0 in reply to Ivan Salazar
    Prodigy 10 points

    Hi,

    I remove low-pass filter(R202/R210->short,C170/C178->NC) when I did these three tests.

    you think results from test 2 are OK means attenuation -1.375dB at 20Hz is normal for DRV632?

    I uploaded schematic of new resistance value configure again with imgur, please try again.

    https://imgur.com/oxrmIJw

    Thanks for your help~

  • +1 in reply to 國元 羅
    TI__Guru** 114535 points

    Hi,

    The frequency response of the device depends on the external components. Input resistor and capacitor form high-pass filter as Fc = 1/(2*pi*14k*1u) = ~11.4Hz. This Fc is at -3dB so ~-1.3dB at 20Hz higher does not sound wrong.

    Let me know if you have any further quesitons.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators

  • 0 in reply to Ivan Salazar
    Prodigy 10 points

    Hi,

    I change C169/C175 with 10u,and attenuation as below

    20->-0.048dB
    1k->-0dB
    20k->0.056dB

    Thanks for your detailed explain~