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DRV5825P: Questions to Fit Piezo Speaker Capacitance in DRV5825 PPC3

Wayne Chen
Guru 16055 points
Part Number: DRV5825P

Hi Sirs,

I tried to fit 10uF Piezo speaker with DRV5825 PPC3 GUI, while it fits as 6.5uF as the pictures below. Would you please tips to resolve it?
Another question, there is no option to change the PWM frequency to 384kHz with 1SPW. Is it an known issue with the PPC3 GUI?

Input 10uF Cpiezo

Fitted as 6.5uF. Is it correct?

Cannot change to 1SPW mode

Cannot reduce Class-D PWM frequency


Wayne Chen
08/11/2022 

  • 0
    TI__Genius 13360 points

    Wayne

    DRV5825 only support BD mode, 768kHz.

    About loop bandwidth un-adjustable, it seems like its a software bug. i will confirm with our software team.

    As the overcurrent and maximum PVDD limitation, at 20khz frequency, DRV5825 can only suffer the max capacitance is 6.5uH.

    otherwise, the oc will trigger.

    tks.

    jesse

  • 0 in reply to Jesse Ji
    Guru 16055 points

    Hi Jesse,

    Thank you for your advise of the capacitance limitation of 6.5uF. Regarding to the modulation, I can  reduce the switching frequency by sending the following commands to the CH-B of DRV5825 EVM successfully. Is there any risk? 

    # 384kHz, 1SPW Mode, Spread Spectrum Enable
    # -----------------------------
    # Enable device
    w 9a 00 00
    w 9a 7f 00
    w 9a 03 0f
    w 9a 00 00
    w 9a 00 00
    w 9a 00 00
    w 9a 00 00

    # Select book 0
    w 9a 7f 00
    # Select page 0
    w 9a 00 00
    # Analog Fault Clear
    w 9a 78 80
    # Fsw=384kHz,1SPW mode, BTL
    w 9a 02 01
    # Enable Spread Spectrum, disable spread spectrum, 0x6b=0x00
    w 9a 6b 03
    # Set Tri-Frequency to 24kHz, Frequency range 336kHz~432kHz
    w 9a 6c 03
    w 9a 03 03

    Thank you and Best regards,

    Wayne Chen
    08/12/2022

  • +1 in reply to Wayne Chen
    TI__Genius 13360 points

    Hi Chen

    According to datasheet, those register setting is reserved.

    we don't recommend customer using those reserved registers.

    when signal is large, 1spw 1 side is 0, 1 side is large duty cycle PWM wav, it maybe similar to DC so that capacitor been damaged.

    thanks.

    Jesse