TPA3122 - not working. Nothing - diyAudio
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Old 4th April 2011, 03:49 PM   #1
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Default TPA3122 - not working. Nothing

I'm VERY new to DIY amplifiers, but I did obtain a TI TPA3122D2 chip.
I've designed the board (attached) and powered it up using +15V DC.
Nothing happens. No hiss, no audio what so ever.

I'm wondering where I've made the error. I followed the reference design in TI's manual for the evaluation board, SLOU214A.pdf.

Any help would be appreciated.

Thanks!

Brian




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Old 4th April 2011, 04:48 PM   #2
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Sorry to be lazy and check it for You, but..
-> Shutdown pin has to be pulled to high
mute pin has to be pulled to low
in order to make it work.
Make sure You done it.

You might want to remove the resistors and just solder the wires directly to gnd / vcc .
2 volts is the tripping voltage, might not affect anything but still worth a shot.
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Old 4th April 2011, 05:43 PM   #3
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Thanks Arty, I'll certainly check SD and mute pins tonight.
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Old 4th April 2011, 06:35 PM   #4
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SD and MUTE looks OK (amp should be ON with both switches/jumpers open). The power track going to pin10 looks way too thin, but should still work.

What's with C9 and C16 (should be inductors)?

I can't immediately make out any other mistakes that would keep it from working. The layout looks a bit poor; especially the ground fill.

I've built a handful of amps from these chips and they have all worked the first time. They seem almost bullet proof as well.

I used double sided board for mine, using the second side as a ground plane with no ground fill on the track side. Using a ground plane allowed the boards to be made without any jumpers.

Last edited by theAnonymous1; 4th April 2011 at 06:37 PM.
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Old 5th April 2011, 06:00 PM   #5
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The inductors L1 and L2 are present.

I'm going to make a new board with cleaner layout and try again.

I've carefully checked everything, and I don't see the error (yet).

Very frustrating.
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Old 5th April 2011, 10:33 PM   #6
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C7 is *way* too far away from Pin1,Pin20. Remove your .1uF monolithic caps from their current locations. Solder .1uF mono caps right across Pin1-Pin20, Pin10-Pin11, and Pin7/8-Pin16/17.

Your power trace to PVCCR (Pin10) is too thin. Solder a 24G (or larger) wire from Pin10 to VCC.

I also recommend decoupling AVCC from PVCC through a small resistor (100-220 ohms is good). In my circuit I also increased the 10uF power cap on AVCC in the reference schematic to 100uF for greater immunity to drops in PVCC voltage.

And the ROUT trace in your PCB is too thin. This won't affect if the chip works or not, but LOUT/ROUT should be as thick as possible to minimize voltage drops in your audio out.
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Old 6th April 2011, 12:56 AM   #7
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http://focus.ti.com/lit/ug/slou214a/slou214a.pdf

Use that as a guide, if it works for TI, it should work for you.
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Old 6th April 2011, 10:41 AM   #8
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Quote:
Originally Posted by killerbobjr View Post
C7 is *way* too far away from Pin1,Pin20. Remove your .1uF monolithic caps from their current locations. Solder .1uF mono caps right across Pin1-Pin20, Pin10-Pin11, and Pin7/8-Pin16/17.

Your power trace to PVCCR (Pin10) is too thin. Solder a 24G (or larger) wire from Pin10 to VCC.

I also recommend decoupling AVCC from PVCC through a small resistor (100-220 ohms is good). In my circuit I also increased the 10uF power cap on AVCC in the reference schematic to 100uF for greater immunity to drops in PVCC voltage.

And the ROUT trace in your PCB is too thin. This won't affect if the chip works or not, but LOUT/ROUT should be as thick as possible to minimize voltage drops in your audio out.
Thanks for the advice. I clearly did not spend enough time studying TI's reference design when I did my board layout. I'm learning now that you can't rush this stuff. I'll try your recommendations.
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Old 6th April 2011, 01:08 PM   #9
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Quote:
Originally Posted by aviatorbja View Post
Thanks for the advice. I clearly did not spend enough time studying TI's reference design when I did my board layout. I'm learning now that you can't rush this stuff. I'll try your recommendations.
It's not necessarily about not being able to 'rush' things. You can do things like this very quickly, the trouble here is that you need to learn good PCB design practice, which in itself can take a lot of time.
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Old 6th April 2011, 03:15 PM   #10
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Default Pin 7/8 tied to ground?

Quote:
Originally Posted by killerbobjr View Post
C7 is *way* too far away from Pin1,Pin20. Remove your .1uF monolithic caps from their current locations. Solder .1uF mono caps right across Pin1-Pin20, Pin10-Pin11, and Pin7/8-Pin16/17.

Your power trace to PVCCR (Pin10) is too thin. Solder a 24G (or larger) wire from Pin10 to VCC.

I also recommend decoupling AVCC from PVCC through a small resistor (100-220 ohms is good). In my circuit I also increased the 10uF power cap on AVCC in the reference schematic to 100uF for greater immunity to drops in PVCC voltage.

And the ROUT trace in your PCB is too thin. This won't affect if the chip works or not, but LOUT/ROUT should be as thick as possible to minimize voltage drops in your audio out.
According to the data sheet, pins 7/8 (analog ground) don't get connected to 0.1uF capacitors.
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