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Old 20th March 2017, 10:58 AM   #1921
irribeo is offline irribeo  Netherlands
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Why not use the Fsw TI tells everone will give lowest THD ? Because someone posts 1MHz sounds better ? Like the 36dB gain sounds better ?
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Old 20th March 2017, 11:29 AM   #1922
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No, because the Volt+ is running at 1MHz BD, thats why.

Another thing i'm interested in is the increased THD at around 1Vrms.

Setup:
PVCC: 19V
Gain: 20dB
Load: 4R6 resistive
Stock board, only changed inductors.

For this i tested several different inductors:
Click the image to open in full size.

The influence of inductance is shown here, 10uH vs 15uH. The "bubble" is flattened and shifted to higher levels:
Click the image to open in full size.

Different geometries/material at the same inductance:
Click the image to open in full size.

Lower inductance will shift the "bubble" a bit to the lower end:
Click the image to open in full size.

Surprisingly the small Codaca CSD1013B dual inductor performed really well, even compared to its more expensive competitor from Coilcraft, the GA3416.

Click the image to open in full size.

Compared with fig.8 of the TPA3118 data sheet (yes it's BTL), the cheap clone is close to EVM performance with the MSS1278-10uH yet. But of course, comparing PBTL with BTL at the different PVCC/Gain settings isn't accurate.

If now we can get rid of the bubble please.
Attached Images
File Type: png Inductor_Comparison_All.png (19.8 KB, 241 views)
File Type: png Inductor_Comparison_10_vs_15.png (16.4 KB, 236 views)
File Type: png Inductor_Comparison_10.png (24.2 KB, 236 views)
File Type: png Inductor_Comparison_3_vs_10_vs_15.png (22.5 KB, 236 views)
File Type: png Inductor_Comparison_Dual.png (24.6 KB, 237 views)
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Old 20th March 2017, 12:39 PM   #1923
irribeo is offline irribeo  Netherlands
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Being close with pbtl and with mss-inductor also to btl 3251evm with same inductors already is very good. Board is a little small to easily implement a compact, I know you like them, bootstrap snubber/ prefilter snubber

Main ceramics in outputfilter probably cause some distortion, because also TI tells us. And TI doesn't use single ended input testing/measuring.

The high esr inputcaps they use might help grounded negative (in single ended) input too ???
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Old 20th March 2017, 12:44 PM   #1924
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Yes, changing fSW is also pita.

I tried better/different ceramics in the output, can't measure any advantage out of it.

At higher levels, inductor saturation dominates while at lower levels inductance and geometrical construction seem to set the rules.
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Old 20th March 2017, 01:43 PM   #1925
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Regarding input caps ESR, i put in 1k brake resistors between them and the TPA pins.. nope.
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Old 20th March 2017, 11:48 PM   #1926
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Anyone wants to join in?

Mainly 0402 components.

Selectable Gain (20-36dB) 0R-Jumpers
Selectable fSW 400-1200kHz 0R-Jumpers
BTL/PBTL 0R Jumpers
2u2F Softterm input coupling caps (low noise, automotive)
PBTL with parallel inductors (2x2) 0R Jumpers
Diff/SE Inputs
Anti-Pop-Circuit
BS-Snubbers
EMI-Snubbers
AGND island for AFE
AVCC RC-Filter
LC-Filter or Ferrite+C filter or filterless
Master/Slave/Daisychain synchronisation
44x35mm (Length x Wide)
High-Current connectors for PVCC and outputs 2x3 Snap-in
4x M3 (3.2mm) mounting holes
Mute/Shutdown input
opt. LED for power/fault
opt. hickup-mode
No polarity protection
Smaller than Volt+


Click the image to open in full size.
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File Type: jpg TPA3116_Flipper_AliG.jpg (80.5 KB, 259 views)

Last edited by doctormord; 20th March 2017 at 11:58 PM.
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Old 21st March 2017, 12:00 AM   #1927
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Quote:
Originally Posted by doctormord View Post
Smaller than Volt+
It is funny to see that opinions have changed. Your design lacks the cap multiplier though.

If you are looking for testers....
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Last edited by jean-paul; 21st March 2017 at 12:03 AM.
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Old 21st March 2017, 12:54 AM   #1928
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Quote:
Originally Posted by jean-paul View Post
It is funny to see that opinions have changed. Your design lacks the cap multiplier though.

If you are looking for testers....
Could you provide a link to TI dealing with cap multipliers, please?
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Old 21st March 2017, 01:15 AM   #1929
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Quote:
Originally Posted by jean-paul View Post
It is funny to see that opinions have changed. Your design lacks the cap multiplier though.

If you are looking for testers....
What/Which opinions have changed?

I have no opinion about the Volt+, i still just wonder how they achieved this THD-levels at 1MHz..

I'm pretty sure it's not the cap multiplier. (Or as others have mentioned, it doesn't help much with noisy SMPS)
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Old 21st March 2017, 09:39 AM   #1930
alkasar is offline alkasar  France
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agreed. cap multiplier is a mean, not an end.

Quote:
Originally Posted by doctormord View Post
Anyone wants to join in?
maybe...
you earlier said this board will be produced by a manufacturer, not soldered by hand. Are you looking for contributors for the prototypes ?
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