HD3SS3412A: Question about connectivity

AI:

    on the left side, did you connect to Gnd?  A to B or A to C depends on SEL status.

Regards,

brian

Dear Brian, 

Sorry, I don't quite get your question, are you talking about A0-, A1-, A2- and A3- should be connected to ground? 

Also, yes I understand for switching, I need to control SEL pin, but by default A and B should be connected.

Thank you.

AI:

    I just saw something on  your schematic, are they just test point?

   By default, you mean SEL is low?

Dear Brian,

The blue circle is actually SMA connectors, i want to inject signal with signal generator. But before I do that, I want to do connectivity test with multimeter, how do I do that? 

By default, what I mean is when SEL is low, that is correct.

Thank you very much! 

when SEL is low, A0+  should be connected to B0+ with around 10 ohms. Did you solder ground pin to thermal pad together?

Regards,

brian

Dear Brian,

I have checked, the thermal pad is grounded. And I got 0 ohms when probing A0+ and B0+. Is there a specific setting I need to do on the switch instead?

Next, I have done some testing where I inject 3.3V at A0+ and connect B0+ and B1+ to ground. From here, I can measure 3.3V when probing A0+ and B0+/B1+, the weird thing is that both B0+ and B1+ always shows 3.3V when probing regardless of the switching outcome. Did I test this wrongly?

Please Advice and thank you.

AI:

    Normally don't directly connect B0 to gnd, pls adding 50 ohm  to test .

    Also max differential voltage is 1.8v, means single ended is 0.9v, 3.3v is too much for the device.

   It's better to input ac signal to A0+ and monitor B0+ on scope.

  B1+ should be related to A1+.

Regards,

Brian

Dear Brian,

Good evening, sorry for the late reply because I have finally setup the signal generator and oscilloscope. The signal generator is generating LVDS 1.8V and 500MHz .

I connected the signal generator on the green font and then connected the Oscilloscope on the red font. However, it shows no signal at all. I have done the following:

1) Oscilloscope fully calibrated.

2) Used different HD3SS3412A to make sure I am not working on a spoiled IC.

3) Tested the signal generator by connecting directly to the oscilloscope to make sure signal generator is not a problem.

4) I have double checked the datasheet and all pin configuration looks okay (please take a look as well).

5) I have confirm thermal pad is connected to ground

Can you please advice me what to do for me to get signal at the oscilloscope?

Thank you very much!

Pls try 0.8v input signal and set SEL high or low.

Regards,

brian

Dear Brian,

I am just curious, 1.8V and 0.8V input signal is different? I tried with 1.8v input signal and I set high and low but the result is the same. However, when I reverse the position (figure below)... I get a huge difference reading, about 1.2mV! What is the explanation on this, I am quite confuse why it reacted that way.

Please advice.

Thank you very much!

max differential spec is 1.8v, means single ended is 0.9v.

If your application is 1.8v single ended, then this is not the right part.

Regards,

brian

Dear Brian, 

I do not have 0.9V supply at the moment but while I search for it, I want to ask what is this VBUS? I don't see any explanation on what is it except the tracer need to carry 2A, is this a possible root cause?

Thank you very much!

Sorry, it's a mistake. We need to correct it.

Regards,

Brian