TMUX1208: PART NUMBER : TMUX1208

This sounds as if the noise comes from pin 8. Is it connected to anything that might generate noise? Can you show an oscilloscope trace of those pins?

Hi Jayanthan,

Is it possible for you to provide oscilloscope screen captures of the address pins, drain pin(D), and the source (S) pins you are using? What is the VDD and EN voltage levels? With more information we can give more accurate recommendations for debugging your circuit.

Thanks,
Tyler

Hi Tyler,

Thanks for your reply,

VDD = VEN = 5V, Address lines are powered at 1.8V.  

Here is the input signal at source line, when all address lines are don't care.

Here is the output signal at Drain, when address lines are configured.

I'm getting same thing at the input Source pin, when address lines are configured.

HI Ladisch,

Thanks for your response,

Here is the input signal at source line, when all address lines are don't care.

Here is the output signal at Drain, when address lines are configured,I'm getting same thing at the input Source pin, when address lines are configured.

Hi Jayanthan,

For your first capture, when you say the address lines are don't care, are they left floating?

For the second capture, it sounds like you are seeing the desired result where the output waveform matches the input waveform.

Thanks,
Tyler

Hi Tyler,

In the 1st capture, address lines are left floating.

if I select A2=0,A1=0,A0=0 , now S1 is selected. at this time, I'm getting 2nd capture (attached already in previous reply) as output at S1 & D pin. If I change my input to S2 & unchanging the address lines , I'm getting correct output(as input) at S2. at a time, I'm getting 2nd capture (attached already in previous reply) as output at D pin(Now, Input is given at S2 line & Address lines remain unchanged). 

Irrespective of the input at Sx, I'm getting output at Drain pin

Problem arises only when the address lines are configured. There is no noise at source line , when address lines are don't care. 

Thanks,

Jayanthan

You must never allow the address inputs to float. If necessary, add pull-up or -down resistors.

You did not answer my question about what is connected to pin 8. Try disconnecting it (remove R7).

Hi Jayanthan,

The address lines cannot be floated, they have to be pulled up or down. Do you have another device which you can test your circuit with? Is it possible that the device you have been using has been damaged?

With the address pins configured, you should not see signals from unselected source pins(Sx) at the drain(D). The multiplexer is a bidirectional, passive device which should not introduce any noise.

Thanks,
Tyler

Hi Clemens,

I'm feeding the input( square wave 500Hz) at say, S3. I'm checking the input at S3 using oscilloscope . I'm what the exact square wave at S3 pin. At this time address lines are A2=A1=A0=0(GND), now, if I change the address lines to A2=0,A1=A0=1, then D must connect to S3, now inpout at S3, should reflect at D. But I'm getting some noise (refer second capture attached previously). After that, I removed the input at S3, then also I can observe noise at D with lower Peak-to-Peak value. 

2. R7 is removed. then also, I'm facing same issue.

Thanks,

Jayanthan

Hi Tyler,

Sorry for the wrong information. Address pins are pulled down

The noise must come from somewhere. The most like candidate is whatever is connected to D; other possibilites are power/GND or other S pins, but those would have to be very strong.

I isolated Drain pin. then also I'm getting noise

Hi Jayanthan,

If you put EN at GND, essentially turn off thew switch, is the noise present at D?

Thanks,
Tyler