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TAS5630 output inductor

Pierre Watts
Prodigy 155 points
Other Parts Discussed in Thread: TAS5613, TAS5630, TAS5611, TAS5631, TAS5614

Hi,

I'm using the TAS5630DKD with PSU rails at 40VDC. Power requirements are low at 90W/ch in 4ohms.

Implementation is very similar to the evaluation board, but due to severe space limitations I had to use a smaller inductor that I saw mentioned elsewhere on the TI forum for a TAS5613, the Coiltronics CTX10-2-52-R (10uH ,4.7A). Capacitors are Panasonic ECW-F2684JAQ (680nF 250V MKP)

Even though they do work and I managed to push a fair amount of power through them, plus the output waveforms look OK.

Unfortunately, the inductors get scorchingly hot, as in >70degrees Celsius without ANY input signal or output load.

Any help would be appreciated.

 

  • 0
    TI__Guru**** 189399 points

    Hi, Pierre,

    Sorry, we missed your post.

    Did you get this worked out?

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 155 points

    Hi Don,
    Yes, it turned out to be a simple case of excessive core losses - guess that was my fault for not calculating it myself and just settling on an unconfirmed suggested product. We eventually settled on a custom toroid that was fairly similar to the one used by the TAS5630 EVM. Messed up the entire space profile but we had no choice.

    From subsequent reading on the forum it appears that my situation was by far not unique and several engineers are frustrated by the lack of suitable or suggested COTS inductors for the TI amplifier range. In addition, custom-wound inductors are often impossible for a product, either because of cost, labour or time-to-market constraints so even though the custom chokes suggested in the datasheet and EVM might be the best for the application, for the engineer it's a headache when there isn't a suggested off-the-shelf product for quick prototype evaluation or manufacturing deadlines.

    I therefore recommend that TI would consider adding a few suggested readily-available COTS inductors to the TAS56xx amplifier datasheets or app notes, along with the limiting parameters of each (power, temperature rise, core loss, ohmic loss etc.) to simplify development with these products.

  • 0 in reply to Pierre Watts
    TI__Mastermind 18510 points

    Pierre, we actually have almost completed developing off-the-shelf inductors for TAS5630, TAS5631 and the rest of their family (TAS5611/2/3/4).  I am checking with the vendor now to try to confirm that you could use that source.  I will let you know ASAP.  We will also replace the present inductor references in the user guides with their information.

    Best regards,

    Steve.

  • 0 in reply to SteveCrump
    TI__Mastermind 18510 points

    Pierre, I have learned from the vendor, Coilcraft, that they are in final review of the data sheet for  MA5173-AE, identical to the inductor we have been using in TAS5630 EVMs.

    This is a 7uH toroid with Isat >20A, high linearity (so low THD effect), low copper losses and very low core losses (it runs cool to the touch in our EVMs, even with PVDD = 50V.

    You can enter a request for the data sheet now at www.coilcraft.com and it will be sent to you shortly.  They have a couple of hundred pieces in stock and would send you samples on request.

    Best regards,

    Steve.

     

  • 0 in reply to SteveCrump
    TI__Mastermind 18510 points

    Pierre, BTW, Coilcraft are also in final review of the data sheet for  MA5172-AE, identical to the inductor we have been using in TAS5631, TAS5611, TAS5612, TAS5613 and TAS5614 EVMs.

    This is a 10uH toroid similar to MA5173-AE, also with Isat >20A, high linearity (so low THD effect), low copper losses and very low core losses.  The data sheet and samples can be requested the same way as for MA5173-AE.

    Best regards,

    Steve.

  • 0 in reply to SteveCrump
    Intellectual 685 points

    Has TI investigated any of the inductors at http://www.ctparts.com/specs/ctcdtf.asp ? Their specifications seem good for use in a high-power class-D amplifier.

    Russ

  • 0 in reply to Russell May
    TI__Expert 4320 points

    Russell

    The specs for the CTPARTS ctcdtf looks promising, we allways recomend customers to actually measure the performance on a prototype before ordereing.

    if it is a Micrometals Core with material mix -2, http://www.micrometals.com/materials_index.html then it uses the same core as we recomend.

     

    best regards

    Kim N Madsen

  • 0 in reply to Kim Nordtorp Madsen
    Intellectual 685 points

    Their engineering department reports that they also use Micrometals Core with material mix -2.

    I think their smaller parts have sufficient current ratings for the TAS5630 but I am not sure. Their middle-size parts have even higher current ratings but they are slightly larger than the ones in the TAS5630 EVM.

    Russ

     

  • 0 in reply to Russell May
    TI__Mastermind 18510 points

    Russell, if Central Technologies use the MicroMetals T94-2 core in the CTCDTF-094 parts, those parts are almost identical to what we now use in our EVMs.  However, beware of any substitutions.  We have seen inductors that use "T94-2" cores from a different vendor, and those have high core losses (and so high heat dissipation and temperature) and cause increased THD at frequencies above 1kHz.

    I think CT are indicating the MicroMetals T94-2 core when they say "10 permeability Carbonyl MicroMetals Core".  If you can confirm absolutely the MicroMetals T94-2 core, the parts should be fine.  But, as Kim said earlier, check performance of samples before buying any quantity.

    Best regards,

    Steve.

     

  • 0 in reply to SteveCrump
    Intellectual 685 points

    Email from me to Central Technology, citing Kim Madsen's 10-06-2011 post:

    Please verify what material is used in the CTCDTF-series of inductors and maybe how it compares to the one they cite.

    ----

    Central Technologies reply:

    This is the response I received from engineering:
     
    Yes. We use the Micrometals -2 mix exclusively on the CTCDT line
    -----
    Their specs include different information from that in the Coilcraft specs, so it is hard to compare them directly. In general their specs look good. The main curious part is their temperature limitation.

    We have not tried them yet and we have no good way to measure THD rigorously but we are not much interested in fundamental frequencies above 400Hz because the application is not audio. We have samples of their 10uH and 15uH middle-size parts which I think I can fit in a TAS5630DKD2EVM for lab experimentation. Our design originally assumed a TAS5615DKD so the higher inductance should not be a problem. Our board is starting PC layout (soon I hope) so I intend to leave room for the middle-size parts.

    Russ


  • 0 in reply to Russell May
    Intellectual 685 points

    By "middle-size" I am refering to their CTCDTF-106xx parts.