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What is the limit of TPA3130D2 voltage output?

MARTIN JONSON
Prodigy 40 points
Other Parts Discussed in Thread: TPA3130D2EVM, TPA3130D2, TPA3116D2, TPA3118D2, TPA3116D2EVM

Hi,

I’m using a TPA3130D2EVM that I modified to run mono mode, I also increased the capacitors to 2*1.5mF. I’ve added an external filter with 2*100uH and 1uF. The load is a coil 1.3uH and 3.75 ohms.
I’ve tried to get enough output power using different amplification settings but I’m not able to get more than 40V swing over the load. Using a 24V power supply I would expect to get much closer to 48V. Max frequency is 500Hz so the voltage drop is only by a small part explained by the filter.
I get fairly symmetrical clipping when using sinus input.
Isn’t TPA3130D2 expected to support rail 2 rail output?
Will I get a better result using TPA3116D2 instead or does it have the same limitations?
Are there a input amplitude/amplification setting that will work?
Please advice

Martin

  • 0
    Genius 3295 points
    Hi Martin,

    What is your input voltage, Vp-p? The input voltage gain stage must be high enough to drive the output correctly. Also, the power supply being used has to have sufficient current to support the load.

    The device's gain is only set upon power-up, so if you make changes to the gain setting resistors you must cycle power each time. Also, input impedance changes with gain; the EVM does not have a preamp so it is assumed that you have one in your circuit. At the very least, I would use a non-inverting buffer on the input to the PA so that you can remove the input impedance variable of the PA from the equation. The "buffer" can also have some gain.

    Mike T.
  • 0 in reply to Mike Tripoli
    TI__Expert 5000 points

    Hi, Martin

    • In your test, with 2 100uH inductor, usually this large inductor has large DRC (maybe 0.3ohm), so the Total Rs should be 0.3*2 (DCR of 2 inductor)+0.12 (Rdson of Class D)=0.72ohm at least.
    • With PVCC=24v, the max un-clipping Vout  should be 24*(3.75/(3.75+0.72))= 20.13V, That is why your max swing voltage is 40v.                                                  Suggest you use some smaller inductor with smaller DCR and have a try.  BTW, it seems your application is not a low output power,  20^2/(3.75*2)=  53.3W, I think you should select TPA3116D2 with heatsink. But of course you can use TPA3118D2 and have a try.     

  • 0 in reply to Peter Cao
    Prodigy 40 points

    Hi,

    Thanks for the replies. After reading them it is my understanding that I should expect rail to rail output capability (– 2*Rdson-Filter impedance)* I. Is that correct?
    I’ve got some ground noise around 2.8kHz that can’t be removed until I make a new layout that’s why I use the bigger coils I've done some more measurements on a new TPA3116D2EVM using only the filters already mounted. Looking at output rails one at the time clipping seems to be asymmetrical. I get very close to GND but not as high as I expect. Another thing is that I get clipping on negative output before I get it on the positive. I added 1mF at the power rail and gained close to 0.5V Vpp on each output rail. Maybe I can gain even more by adding more cap closer to supply pins. Today it is added at supply terminals. I am close now to reaching desired output level. There is just 1.5V voltage drop on positive "peak" on each output.

    BR
    Martin