LM4950 Cross Talk problem

Anand Sethi

Other Parts Discussed in Thread: LM4950

I am using two LM4950 on a board powered by same main source power supply. These amps are in a high gain mode but the signals cross talk quiet a bit. I have seprate ground and power back to the source. The supply for one is going through a linear regulator. I was wondering why is there a cross talk. Moreover is there an active circuit solution to reduce cross talk. I need to be 75 db down. I though PSRR etc would help me out but that is not the case. I need some suggestion or guidance to an active circuit to reduce this problem.

over 10 years ago

0 Don Dapkus over 10 years ago

TI__Guru**** 189401 points

Hi, Anand,

That's odd. Try separating the power supplies more. Can you add more decoupling to each one?

Can you verify that the issue is coming from the power supply? Can you power one from a bench supply or something to prove that the issue is coming from the power supply?

-d2

0 Anand Sethi over 10 years ago in reply to Don Dapkus

Prodigy 135 points

Hello Don,

Thanks for the response. I veriied that by using an external supply and the cross talk went down in the -80 db range. I also have linear regulator on one of the amps to reduce it but it still does not work. I was thinking maybe the noise is on the ground and evades the linear regulator which should potentially act as LPF. Is there an active way of cancelling this ripple or I am I doing something wrong.

Thanks,
Anand

0 Don Dapkus over 10 years ago in reply to Anand Sethi

TI__Guru**** 189401 points

Hi, Anand,

This sounds like a PCB layout issue. Look at your ground plane to see if that is where the noise is coming from.

-d2

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LM4950 Cross Talk problem