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Old 1st February 2013, 09:21 PM   #1
danny92 is offline danny92  Portugal
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Default TDA7297 input ground

Hello everyone,

I'm thinking about making a PCB for a design with TDA7297, I know that with other TDAs, and I think this one is not an exception you have to connect input ground near the TDA at the same PCB, I don't know if I can connect the input ground at the power supply star ground point (which seems better), I've tried to simulate both situations in breadboards and I've only obtained good results when the input ground is connected near the TDA7297 IC (the problem is the very poor impedance characteristics of breadboard conductors). Can anyone help me solving this problem?
I've never made a PCB before, I've only mounted several low power audio opamps (always on breadboards) and I'm afraid of making a PCB that doesn't work like expected.
PCB layouts (Power Supply, TDA7297/TDA2822M and respective voltage regulators) attached to this post.

Thank you very much for your atention,
Best regards,
Daniel Almeida
Attached Files
File Type: pdf tda7297(gnd6).pdf (36.3 KB, 62 views)
File Type: pdf Single Power Supply2 (TDA).pdf (16.1 KB, 42 views)
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Old 2nd February 2013, 10:54 PM   #2
gootee is offline gootee  United States
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You would always want the input ground conductor to stay very close to the input signal conductor, anyway. Otherwise you will be creating "enclosed loop area" which will make an antenna.

You should tightly twist the input signal and input ground wires together, all the way from the input jack to the pcb. Input jack must also be isolated from chassis, so input ground does not get connected to chassis, accidentally. Even better: Use shielded twisted pair, with input signal and input ground on twisted pair, and shield connected to chassis, at one end only, and connected to nothing on the other end.

On the PCB, keep input and input ground traces very close together, with minimal gap between them, everywhere. Pour copper for input ground so that it surrounds all input signal traces and related components.

Input ground on PCB should have separate connection back to star ground, i.e. not mixed with power ground.

Last edited by gootee; 2nd February 2013 at 10:59 PM.
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Old 5th February 2013, 09:03 PM   #3
danny92 is offline danny92  Portugal
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Thank you very much for your reply, I will follow your advices,
Best regards,
Daniel Almeida
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Old 1st April 2013, 10:18 PM   #4
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Join Date: Mar 2009
Default Just bought an amp using the 7297

Danny,

It's REALLY good. You won't regret any effort you put into using it.

I started a thread on the class D amp section http://www.diyaudio.com/forums/class...han-lunch.html about this amp pictured below.
Good luck!
Mark
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Old 1st April 2013, 11:37 PM   #5
danny92 is offline danny92  Portugal
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Location: Lisbon
Thank you very much
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