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-   -   TPA3251d2 (https://www.diyaudio.com/forums/class-d/276982-tpa3251d2.html)

Capt Grogg 11th July 2015 03:18 PM

TPA3251d2
 
TI has released TPA3251d2 'AKITA" higher power analog in class D chip with higher order modulator similar to Hypex NCore but with pre filter feedback. First heard about it at CES 3+ years ago. Can be configured as 1,2,3 or 4 channel with 36 volt supply for output stage.

egra 11th July 2015 05:44 PM

I'm really curious how this chip sounds. Pretty impressive description:

"TPA3251D2 is a high performance class-D power amplifier that enables true premium sound quality with class-D efficiency. It features an advanced integrated feedback design and proprietary high-speed gate driver error correction (PurePath™ Ultra-HD). This technology allows ultra low distortion across the audio band and superior audio quality."

I hope the chinese manufacturers will take the first steps soon.

frammis 13th July 2015 11:57 PM

TPA3251D2 THD Curves
 
2 Attachment(s)
This is a closed loop part with pre-filter feedback. THD vs power (at 1KHz) & THD vs Frequency curves from June 2015 datasheet attached. I'd like to try a differential input, BTL output implementation.

TI website has samples: TPA3251D2 | Mid/High-Power Class D Amplifiers | Audio | Sample & buy

doctormord 15th July 2015 12:10 AM

Yeah, let's make a small board <=10x5cm. :)

doctormord 16th July 2015 01:47 PM

Some short calculation for the required heatsink, worst case:

Rds_on (high/low side): 0.1R
Imax: 14A
Tambient: 30C
Rth_jc(Top): 0.36C/W

Power dissipation per channel:

Pd_channel = IR = Imax*2*Rds_on = 14A*2*0.1R = 196A*0.2R = 39.2W

Power dissipation total:

Pd_total = 2*Pd_channel = 2*39.2W = 78.4W

Tcase = Tjunction - Rth_jc * Pd_Total = 125C - 0.36C/W * 78.4W = 125C - 28.224C = 96.776C

Rth_heatsink = (Tcase - Tambient) / Pd_total = (96.776C - 30C) / 78.4W = 0.85C/W

Rth_heatsink includes thermal conductivity of heatsink grease.

--------------

Lets do the calculation again for Irms (sinus power):

Rds_on (high/low side): 0.1R
Imax: 14A

Tambient: 30C
Rth_jc(Top): 0.36C/W

Power dissipation per channel:

Irms = Imax*sqrt(2) = 14A*0.707 = 9.9A

Pd_channel = IrmsR = Irms*2*Rds_on = 9.9A*2*0.1R = 98A*0.2R = 19.6W

Power dissipation total:

Pd_total = 2*Pd_channel = 2*19.6W = 39.2W

Tcase = Tjunction - Rth_jc * Pd_Total = 125C - 0.36C/W * 39.2W = 125C - 14.112C = 110.888C

Rth_heatsink = (Tcase - Tambient) / Pd_total = (110.888C - 30C) / 39.2W = 2.1C/W

Rth_heatsink includes thermal conductivity of heatsink grease.

Much better. :D

As music is normally not pure fixed frequency sine wave the maximum temperature will likely not reached even at full power.

----------------------------------------------------------------------
Lastly, for normal use, with an estimated programm factor of 0.5 there will be:

Rds_on (high/low side): 0.1R
Imax: 14A
Music programm factor (mpf): 0.5
Allowed max junction temperatur: 90% from Tj = 0.9*125C = 113C

Tambient: 35C
Rth_jc(Top): 0.36C/W

Power dissipation per channel:

Irms = Imax*sqrt(2) = 14A*0.707 = 9.9A
Iprog = Irms * mpf = 4.45A

Pd_channel = IprogR = Iprog*2*Rds_on = 4.45A*2*0.1R = 19.8A*0.2R = 3.96W

Power dissipation total:

Pd_total = 2*Pd_channel = 2*3.96W = 7.92W

Tcase = Tjunction - Rth_jc * Pd_Total = 113C - 0.36C/W * 7.92W = 113C - 2.85C = 110.15C

Rth_heatsink = (Tcase - Tambient) / Pd_total = (110.15C - 35C) / 7.92W = 9.5C/W

Buehgemeiste 16th July 2015 01:49 PM

Quote:

Originally Posted by doctormord (https://www.diyaudio.com/forums/class-d/276982-tpa3251d2-post4390342.html#post4390342)
Yeah, let's make a small board <=10x5cm. :)

Please do that!!!
Most of the commonly used chips are 5+ years old.
Did you see the TAS57xx series with integrated DSP stuff?
If i were an engineer...

doctormord 16th July 2015 03:08 PM

Sorry, but i can't find them on the TI page. (With analog inputs)

Buehgemeiste 16th July 2015 03:12 PM

this is one ds:
http://www.ti.com/lit/ds/symlink/tas5756m.pdf

this is the user manual for the software:
http://www.ti.com/lit/ug/slau577a/slau577a.pdf

doctormord 16th July 2015 04:02 PM

Thats something totally different. Digital Inputs, less output power, less operating voltage..

Buehgemeiste 16th July 2015 04:29 PM

yes


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