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MAX98390 Dynamic Speaker Management limit Setting

Category: Software
Product Number: MAX98390
Software Version: v1.5.1.0

Dear Sir

Use the DSM tool for MAX98390 EVK to set the Vdrx, play the 1Khz sing wave, and use the 4Ohm cement load + Low pass filter to measure the output waveform with an oscilloscope.
Then adjust the Volume upwards,
It was found that the output can still exceed the set voltage of Vdrx and is not limited to clipping.
My understanding is that Vdrx should limit the output limit, and the part exceeding the setting should be protected by clipping.
Is this current phenomenon normal?
How should I set it to achieve the condition of Output power limit = 2W /4Ohm?

  • Hello FrankChu19830219,

    Yes, for your test condition, this is normal. Vdrx is the voltage at which a sealed speaker sub-unit will reach its maximum excursion, it does not directly set the limit of the amplifier's output. The MAX98390 uses a model of the speaker's acoustic performance to limit the excursion of the speaker at the appropriate frequencies and volumes, one of the parameters of this model is the Vdrx value. 

    The overall power to the load can be limited by setting the static digital volume control to a value that meets this limit. 

  • Dear Andrew 

    Thank you for your explanation, I think I understand I think I understand the limiting principle of Vdrx

    Thank You

    Frank