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TAS5624A Value of Bootstrap Capacitor

Sadanori Kato
Guru 36490 points
Other Parts Discussed in Thread: TAS5624A

Hi,

I understood that TAS5624A is recommended to use 0.033uF ceramic capacitors for the bootstrap supply as the following post.
We are considering to increase the value of the bootstrap capacitor by reducing the ripple voltage for the gate-drive circuit to improve the sound quality.
So, we have some questions.
Do you have the experience that increased bootstrap capacitors ?
In addition, do you have trouble examples ?
Please tell us if there is the available maximum value for them.

http://e2e.ti.com/support/amplifiers/audio_amplifiers/f/6/t/478196

Best regards,
Kato

  • 0
    TI__Guru 57800 points

    Hi, Kato-san,

    I asked my colleague to check your questions, he will get back to you early next week after Holiday.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Guru 36490 points

    Hi Diego-san,

    Thank you for your quick response.
    I am looking forward to getting the information from you.

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    Guru 36490 points

    Hi Diego-san,

    Please let me know if you have any updates on my question.

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Genius 9175 points

    Hello Kato-san,

    I apologize for the delay. I was out for holiday.

    Generally it is not recommended to change the bootstrap capacitor value. The TAS5624A was designed and tested with 33nF capacitors. This is standard for our devices. Channing this value may cause the part to not function properly at very high and very low PWM modulation levels.

    Also, the bootstrap capacitor will have little impact on audio quality. Typically the loop filter, loop gain, and architecture of the amplifier determines overall performance level.

    If your customer is looking fro better performance, I would recommend the TPA32xx family of device.

    Best Regards,

    Matt

  • 0 in reply to Matthew Beardsworth
    Guru 36490 points

    Hi Matt-san,

    Thank you for explaining so politely.
    I have one additional request.
    Could you please share the detailed information to me if you have the experience regarding the trouble information which occurred by increasing the bootstrap capacitor in the market ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Genius 9175 points

    Hello Kato-san,

    If the bootstrap capacitors are too large, we have seen that the cap does not charge up to the full GVDD supply level when the PWM output is low. The RC time constant is too long. Therefore, as the PWM transitions high the bootstrap cap may not hold the high-side gate on for the full length of the PWM.

    This is especially true at high modulation indexes (high output power) where the PWM is low for a very short time and high for a long period of time. This will cause dropout issues at high power.

    Best Regards,

    Matt

  • 0 in reply to Matthew Beardsworth
    Guru 36490 points

    Hi Matt-san,

    Thank you for explaining so politely.
    I understood and will inform our customer of your information.

    Best regards,
    Kato