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TPA2100P1 evm driving Murata Piezo speaker

chrisw957
Intellectual 480 points
Other Parts Discussed in Thread: TPA2100P1

Should the TPA2100P1 EVM be able to directly drive a Murata piezeo model VSLBG1914E1400-T0?

http://search.murata.co.jp/Ceramy/CatalogAction.do?sHinnm=?&nbsp&sNHinnm=VSLBG1914E1400-T0&sNhin_key=VSLBG1914E1400-T0&sLang=en&sParam=VSLBG1914E1400-T0

It appears to be a fairly standard piezo speaker, 0.9uF, 200 to 20khz, etc...

We have it connected, but out+ and out- seem to be exactly the same, so there ends up being no differential signal across the piezo, and we get no audio.

Out signal is around 300khz, 10V square wave when audio is present at the input.

Thanks.

  • 0
    TI__Guru**** 189399 points

    Hi, Chris,

    Hmmm, that's odd. It looks like the TPA2100P1 should be able to drive your piezo. It actually sounds like maybe one of the output filter elements is broken.

    If you look before the output filter (L2 and R5) do you see the outputs in phase?

    Note, they will be in phase with no input signal.

    Also, please note that we have used a shorting input jack on this EVM... If you drive your signal into J2, you must put an RCA plug into the input jack, or it will short out your input signal. That actually sounds like what's going on here.

    -d2 

  • 0 in reply to Don Dapkus
    Prodigy 220 points

    Hi Don / Chris. Just to confirm, we just tested the same EVB a few minutes ago with the same Murata Piezo speaker for a pending design. Our wiring was direct to the RCA jack and after wasting some time, we noted the short between the RCA jack. Thanks for this post - should have read it sooner. After we cut the trace from the "hot" of the RCA jack, the audio is playing from the Murata 1913 Piezo (24 db setting). We are operating the EVB @ 3.3 volts. The TPA2100 is on the approved Murata list of devices. Thanks.

    Kumar

  • 0 in reply to Mon2
    TI__Guru**** 189399 points

    Yay! Sorry we use that pesky RCA jack... 

  • 0 in reply to Don Dapkus
    Intellectual 480 points

     

    Apparently it turned out to be a bad eval kit.  Mouser exchanged it for us, and the new one worked right off the bat.

    Thanks.