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TPA3118D2: small size caps for BRP(N)P/L to OUTP(N)R/L

Katsu Matsunaga
Expert 7730 points
Part Number: TPA3118D2
Other Parts Discussed in Thread: TPA3128D2,

Hello,

 

I have question about size of capacitor between BSN(P)R/L and OUTN(P)R/L.

 

My customer is designing a loudspeaker system with TPA3118D2, and refer TPA3128D2 EVM user guide.

Their design is BTL connection, Vcc:DC25V, Load:3ohm/60W output (peak power 120W)

 

Regarding C15, C16, C17 and C18 of TPA3128D2 EVM, they are 0.22uF/25V GRM188R71E224KA88D (Murata)

The EVM uses 0603(1.6x0.8mm), my customer want to use small capacitor as 0201(0.6x0.3mm) or 0402(1x0.5mm) due to 0603 shortage.

 

Question are below

  1. If they use the small size and the same spec as 0.22uF/25V, is there problem?

  2. If the small size but no exact spec, is it possible to make capacitors connected in parallel?

  3. Voltage rating of the capacitor are necessary over 25V?

 

Best regards,

Katsu

  • 0
    TI__Prodigy 600 points

    Hi Katsu,

    1. Except for capacitance and voltage rating, please also pay attention to material. Quality of X5R or better are recommended, which may be expensive under small package. If these specs are satisfied, then it can be used.
    2. Yes, parallel caps can be used.
    3. Voltage rating of at least 16V is recommended.

    Rgards,

    Hector Zhang

  • 0 in reply to Hector Zhang
    TI__Expert 7730 points

    Hi Hector-san,

    Thank you for your support.

    I would like to confirm about inductor (10uH) in reference design. Is the inductor possible to use? 

    IHLP5050FDER100M01 (Vishay)

    Best regards,

    Katsu

  • 0 in reply to Katsu Matsunaga
    TI__Prodigy 600 points

    Katsu,

    I have checked the current ratings of IHLP5050FDER100M01 and yes, this part can be used for your application, with enough margins. Thanks.

    regards,

    Hector Zhang

  • 0 in reply to Hector Zhang
    TI__Expert 7730 points

    Hi Hector-san,

    My customer would like to confirm about boot strap capacitor below two.

    - voltage rating of the capacitor is recommended over 16V, is this enough for 3 ohm load and 120W?

      Their understanding is that voltage of the capacitor is DC + Pulse factor. So 16V rating looks not enough.

    - Regarding internal circuit, switching FET gate always get 6.9V(GVDD)?  Don't we need to concern an effect from pulse factor(AC?)  and capacitor?

      capacitance is changed by DC bias, so how do we choose capacitor range of 0.22uF?

    Best regards, Katsu

     

  • 0 in reply to Katsu Matsunaga
    TI__Prodigy 600 points

    Katsu-san,

    The BST capacitor sees a voltage difference between OUT and Gate. This voltage difference is basically GVDD, no matter where the absolute OUT voltage goes. So no need to worry about ac pulse.

    Since GVDD is around 7V, as long as the capacitor is chosen with a DC rating of 16V or higher, and with a quality of X5R or better, there is no need to worry about the capacitance drop due to DC bias. A 0.22uF cap should be enough.

    Best regards,

    Hector Zhang