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TPA3250D2EVM: Alternate p/n for inductor and AC coupling cap question

Part Number: TPA3250D2EVM
Other Parts Discussed in Thread: TPA3250, TPA3245EVM, TPA3245, TPA3251

I have (2) questions regarding the TPA3250D2EVM

1. Can you provide an alternate p/n for L2, L3, L4, L5 ( Coilcraft p/n MA5172-AE)? Specifically, I am looking for an inductor that is shielded and more compact.

2. The output AC coupling caps (C21,C34,C42,C56) have the option to be shorted with a jumper. Is the output AC coupling capacitor optional or is the shorting jumper present for possibly relocating the AC coupling capacitor to another location? The TPA3250 data sheet circuit connection diagram (section 10.2.4) does not show an output AC coupling capacitor. I am trying to determine if the output AC coupling capacitor is required for the TPA3250 to achieve optimal performance. 

  • Hi Frank,

    1. I can help direct you better with some more information about the amount of current you are needing. We use the UA8013-ALD on the TPA3245EVM but they also have a 10uH equivalent. The power losses are larger on these inductors but they are very compact and dual core. They might not be able to handle the amount of current you need though. 

    2. These AC coupling capacitors are only needed if you are performing Single-ended output mode. In that configuration, the speakers would see an DC voltage without the AC coupling capacitor. You can see what I'm talking about if you look at the circuit diagram in Section 10.2.3.

    Regards,

    Robert Clifton

  • Hi Robert,

    Thanks for your reply and suggestion on the alternate inductor UA8013-ALD.

    I compared the UA8014-ALD to the  MA5172-AE. The only real difference I see between the UA8014-ALD and the MA5172-AE is the Isat current is lower in the UA8014-ALD. Is this an important characteristic?

    The TPA3245 is a 115 Watt amplifier vs the TPA3250 which is a 70 Watt amplifier. Trying to understand why the UA8014-ALD would not handle the current in the TPA3250 which is a lower power amplifier. Are you saying I need to limit the amplifier output (e.g. by limiting the input)?  

    Thanks in advance.  

  • Hi Frank,

    A general rule of thumb I have is I look at the inductance vs current curve to see how much of a drop in inductance there is at the maximum current that the inductor expects to see. Ideally there is little drop in inductance as you wouldn't want the LC filter to change based on output current! 

    As for the second part. I was thinking TPA3251 instead of TPA3250! Sorry to add confusion to that. These inductors should work for the TPA3250 likely work for TPA3250 by just calculating the maximum current out of the device you expect to see and seeing what the inductors inductance vs current curve shows. 

    Best Regards,

    Robert Clifton