TPA3251D2 - 2 x 175W stereo 350W Mono class-D amplifier

In analogy to the TAS family (TAS5630B, TAS5613A, TAS5611A) Texas Instruments introduced a new class-d chip amplifier, the TPA3251D2 (HTSSOP44).

Specs are:

  • Differential analog inputs 2Vrms
  • Efficiency 90% (4 ohms)
  • 12-36V power supply
  • 2 x 175 Watts into 4 Ohms BTL (10% THD)
  • 2 x 220W into 3 ohms BTL (10% THD)
  • 350W at 2 ohms PBTL (10% THD)
  • 2 x 140W into 4 Ohms BTL (1% THD)
  • 2 x 175W 3 ohms BTL (1% THD)
  • 285W at 2 ohms PBTL (1% THD)
  • Possible configurations are: Stereo (2 x BTL), Quad (4 x SE), Mono (PBTL), 2.1 Stereo Sub (2 x SE 1 x BTL)
  • 100 kHz bandwidth
  • 60dB PSRR, <60uV output noise, >111dB SNR
  • HTSSOP44

Update (05.08.2015): Rev 0.A PCBs are ordered at Elecrow
Update (30.08.2015): Rev 0.A Erstes Testmuster aufgebaut
Update (14.03.2016): “Shrink Mod” TPA3251D2 in 60x60mm

Many thanks to"Fishing electronics“, “Texas Instruments"and"Coilcraft"for the support.

100 x 100 mm² should be possible, cooling might be challeging.

TPA3251D2 mockup

TPA3251D2 mockup

TPA3251D2-KiCAD

TPA3251D2-KiCAD

The fully differential inputs require an external driver, the TPA3251D2 itself has an internal gain of 20 DB.

Simulation

Input level

Variant with a PNP differential amplifier

Differential PNP Inputstage 30V

Differential PNP input at 30V

Differential PNP input at 12V

Differential PNP input at 12V

Variant with operational amplifiers

Differential OPAMP input at 12V

Differential OPAMP input at 12V

Differential OPAMP input at 12V AC

Differential OPAMP input at 12V AC

Differential OPAMP input at 12V FFT

Differential OPAMP input at 12V FFT

Output level

MOSFET Rds_on

Based on data from Texas instruments.

TPA3251D2 MOSFET Rds_on

TPA3251D2 MOSFET Rds_on

Circuit details

Anti-Pop – Spannungsüberwachung

The following circuit is used to avoid noise when switching off the amplifier stage on the EVM. Depending on the used step down converter and power supply that works more or less well. Be observed can, that the "power monitor" must be set to a safe shutdown of noise-free bit "sharper". That through reduction of R31 (> = 33 k < 100 k) as well as parallel connection of a further Widerstandds to # 17. Unfortunately you bought a higher sensitivity to shocks of the supply voltage at higher levels in the event that the power supply can supply enough not "hard" it. In addition, temperature-induced effects arise.

TPS3801 EVM

TPS3801 EVM

Alternatively a circuit can be used, as shown below, - where to set the threshold on the related power supply and whose state of tension.

TPS3801 adjust

TPS3801 adjust

TPA3251D2 – Revision 0.A

Mookups

TPA3251D2 Mockup Blue #1

TPA3251D2 Mockup Blue #1

TPA3251D2 Mockup Blue #2

TPA3251D2 Mockup Blue #2

TPA3251D2 Mockup Blue #3

TPA3251D2 Mockup Blue #3

TPA3251D2 Mockup Blue (vs TPA3132D2) #1

TPA3251D2 Mockup Blue (vs TPA3132D2) #1

TPA3251D2 Mockup Blue (vs TPA3132D2) #2

TPA3251D2 Mockup Blue (vs TPA3132D2) #2

Board layout

TPA3251D2 Rev 0.A front

TPA3251D2 Rev 0.A front

TPA3251D2 Rev 0.A back

TPA3251D2 Rev 0.A back

Test Setup

TPA3251D2 Blue Rev.0A #1

TPA3251D2 Blue Rev.0A #1

TPA3251D2 Blue Rev.0A #2

TPA3251D2 Blue Rev.0A #2

TPA3251D2 Blue Rev.0A #3

TPA3251D2 Blue Rev.0A #3

TPA3251D2 blue Rev. 0A #4

TPA3251D2 blue Rev. 0A #4

TPA3251D2 blue Rev. 0A #5

TPA3251D2 blue Rev. 0A #5

TPA3251D2 blue Rev. 0A #7

TPA3251D2 blue Rev. 0A #7

TPA3251D2 blue Rev. 0A #7

TPA3251D2 blue Rev. 0A #7

TPA3251D2 blue Rev. 0A #6

TPA3251D2 blue Rev. 0A #6

TPA3251D2 – Shrink Mod

Reduction of the system on 60x60mm with active cooling and dual coils.

TPA3251D2 60x60mm PCB #1

TPA3251D2 60x60mm PCB #1

TPA3251D2 60x60mm PCB #2

TPA3251D2 60x60mm PCB #2

TPA3251D2 60x60mm sideview

TPA3251D2 60x60mm sideview

TPA3251D2 60x60mm

TPA3251D2 60x60mm

TPA3251D2 100x100mm vs. 60x60mm #2

TPA3251D2 100x100mm vs. 60x60mm #2

TPA3251D2 100x100mm vs. 60x60mm #1

TPA3251D2 100x100mm vs. 60x60mm #1

Measurement results

Frequency response

TPA3152D2 frequency response

TPA3152D2 frequency response

System temperature

Heat sink temperature for 2x25W and 2x75W compared to the EVM by Texas instruments.

TPA3251D2 - relative temperature (heat sink) without Standoffs

TPA3251D2 - relativeTemperatur (heat sink) without standoffs

TPA3251D2 - relative temperature (heat sink) without standoffs - extrapolation

TPA3251D2 - relativeTemperatur (heat sink) without standoffs - extrapolation

A significant improvement in results when using 8mm of spacers/standoffs under the Board.

TPA3251D2 - relative temperature with / without Standoffs

TPA3251D2 - relative temperature with or without standoffs

The following measurements were carried out with 8 mm of spacers/standoffs under the Board.

System temperature at idle with a special focus on the Coilcraft MSs1210 inductors used.

TPA3251D2 - Temperature idle (heatsink + MSS1210)

TPA3251D2 - temperature idle (heatsink MSS1210)

The following chart gives the Coilcraft MSS1210 relative to the ambient temperature. Interesting here, the temperature decreases to central services (75W per channel).

TPA3251D2 - relative Temperatur MSS1210 (25W/75W)

TPA3251D2 - temperature MSS1210 (25W/75W)

The corresponding heat sink temperature is to:

TPA3251D2 - temperature (heatsink + MSS1210)

TPA3251D2 - temperature (heat sink MSS1210)

Surface temperatures (idle) is summarized in a heatmap.

TPA3251D2 - Heatmap temperature distribution

TPA3251D2 - heat temperature distribution

To be continued, further discussions on stromrichter.org and diyaudio.com.

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43 Responses

  1. Jens says:

    Hi,
    very good looking designs / boards!
    I would be particularly interested in the “TPA3251D2 - Shrink Mod” (60x60mm).
    Do you sell the boards in assembled form and if so, how much do they cost?
    (I don't need potentiometer / volume control)
    Do the boards have a minimum supply voltage?
    Would at least temporarily want to use a 24V power supply.

    Thanks a lot and best greetings
    Jens Degenhardt

    • 360customs says:

      I have maybe 1-2 of the small boards left, I don't have any more in stock, that would have to be done by myself. Write an email if interested. Greetings Christian

  2. peter says:

    Need two TPA3251 assembly module. thanks. Peter

  3. Dean J Halleck says:

    Hi , are there any amplifiers or PCB’S still available???

  4. anubhav sharma says:

    Hello please send me the link to buy the PCB’s

  5. Audiobits says:

    Hi . Can you please tell me how and where where to buy the PCB of 3251? Please reply in my email.

    I’ve been following the progress of your great works since last year.

    Thanks a lot

  6. Ali Cameron says:

    Hello
    I’d like to know more about the pcb price and availability please
    Thanks

  7. Hince says:

    Could you please send me email where to buy the PCB?

    Thank you.

  8. Hince says:

    Hi. Where to buy the PCB of this amp?

    Thank you.

  9. Hince says:

    When is the availability of the complete kit of 3251?

  10. Denis says:

    Hello! Can I buy ready-made modules?

  11. Dimitri says:

    Hi,
    Nice job !
    I need a pcb, please send me a mail.

  12. Paul says:

    Hi,

    I watched the thread about this amp on Diyaudio. It seems awsome.
    I want to buy the pcb. May I have a BOM?

    Thanks.

  13. Karel says:

    I need buy two mini TPA3251 boards or assembly module. thanks.

  14. Andreas Kåll says:

    Love to buy one 🙂

  15. PJ says:

    Where can I buy the pcb? do you have a BOM also?
    Thanks!

  16. ppy says:

    I want to buy too.
    Do you sell only pcb board, or have sets of kit?

  17. Period C says:

    Hi,
    I am regularly checking your progress on 3251d2 here and on diyaudio and I am amazed by the clinical functionality and aesthethics of your designs. I already own a 3116 and I like its sound for such a small and cheap design. I wonder if there are 3251d2 eagle boards/pcbs and BOM available to try to make one myself or even if a complete kit 10×10 or 6×6 with plexi box can be purchased. That would be great. It just looks awesome!
    Thank you!

  18. shaun moloney says:

    also would like to buy pcb what is price and where can i order

  19. Max says:

    You said that the small version is still uder testing phase, but what about the bigger one. Can I buy some of those?

    Thank you

  20. Ct says:

    Any updates on modules for sale?

  21. Thomas says:

    Hello,

    where can I order these things?

    FG

  22. Are we talking of a real product or just of a proof of concept?
    It would be a DIY kit or a mounted product?
    Where and when more info on it?

  23. Georch says:

    Can you measure the IMD parameter and compare with Maxim part?
    I heard that the audio quality of Class-D amp is dominated by IMD.

    Thanks!

  24. jira says:

    I want to buy

  25. Ralf says:

    Hello,

    I will not figure out your site, find it but interesting. What is it with the TPA3251D2 and MAX9708 on himself?
    I'm always on the lookout for new and possibly better digital amplifier modules, have even many of them, currently TPA3116.

    Use their modules to listening to music?
    How do they sound compared with other modules?
    Can I buy ready-made modules?
    I am grateful for any info...

    Thank you and greetings

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