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TAS5756M: Why is TAS5756M advertised as 30W stereo/40W mono, while the TAS5754M is 40W stereo/61W mono?

Joe454
Intellectual 580 points
Part Number: TAS5756M

These are the headings from the main product pages.  But looking at the datasheets, the power handling in both mono and stereo seems to be identical.  I am aware that (supposedly) the only difference is the modulation scheme, but is there any truth that the 5754M can handle more power?  Under what circumstance?

  • 0
    TI__Mastermind 19080 points

    Hi,

    The modulation scheme of TAS5754 is 1SPW. Compared with BD modulation, when outputting high level signal, only one side of the H-bridge is switching in 1SPW. This will help to reduce the power dissipation and can have higher output power before triggering over temperature protection.

    The drawback of 1SPW is as it is single side switching, the THD+N performance is little bit worse than BD modulation.

    Regards,

    Sam 

  • 0 in reply to Sam(MPAA) Zhang
    Intellectual 580 points

    Thanks!  Your comments do make sense and are a plausible explanation, but I am still having trouble finding where this difference is expressed in the datasheets.  It appears that all of the power plots are nearly identical, but perhaps I am overlooking one?

    For example, Figure 25, which shows maximum power @ 10% THD, is identical for both parts.  The other plots, showing THD+N vs power for BTL and PBTL are essentially identical, and certainly don't reflect a ~30%-50% increase in power capacity described by the product page.  The only place I have been able to find this difference in power expressed is in the main 30W/40W headers on the product page.

    Under what conditions do we see a 30%-50% increase in power performance between these parts?

  • 0 in reply to Joe454
    TI__Mastermind 19080 points

    Hi,

    For the you plots you mentioned, like THD+N vs. Power, they are usually measured as quick sweep. As overcurrent limit are the same, it does make sense that they have similar at 10% THD+N Thermal factors are not taking much effect here.

    In short, TAS5754 has higher efficiency due to the 1SPW modulation, thus has higher power capability before triggering OTP.

    Thanks!

    Regards,

    Sam

  • 0 in reply to Sam(MPAA) Zhang
    Intellectual 580 points

    OK, just to be sure, where exactly on the datasheet is the increased power handling shown?  I would have expected a notable difference in continuous tone capacity, for example.

  • 0 in reply to Joe454
    TI__Mastermind 19080 points

    I think so. Datasheet has no other places to mention the long-term power handling capability. Information on Page 12 may help you. Thanks!

  • 0 in reply to Sam(MPAA) Zhang
    Intellectual 580 points

    Ah, that table is what I overlooked, I was focused on the graphs.  Thanks, there are clear differences there.