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Siglent SDS1202X-E ground bounce between channels

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calvingloster:
I am using a microcontroller to get an ADC reading from a 16 bit ADC (LTC2326). The SPI clock speed is set to 500KHZ and im getting massive ringing on the clock, MOSI and MISO lines. this ringing seems to be showing up on channel two which is what I'm using to trigger on. I have added 50 ohm resistors in series to try damp the lines but the ringing and crosstalk is still showing up quite significantly. Is there something wrong with my scope? I tried using a 10X probe on channel two and the crosstalk gets worse.

The setup is on a breadboard and I've tried to keep channel 1 and channel 2 leads separated as much as I can. Ive added a screenshot.

Could there be something wrong with my scope?

Grandchuck:
Try shorter oscilloscope ground leads.

2N3055:
Clock frequency (repetition rate) of 500kHz makes no difference.. That chip can use 100 MHz SPI clock.. Which means it will have sub 1ns edges... Those are seriously fast edges..
Like Grandchuck say, use very short probe wires (use direct spring connection if you can).

Title is wrong.. What you see is not crosstalk between channels but ground bounce...

Crosstalk between channels is what you get if you connect a signal to one ch, and nothing at all to other, and then try to see if you see anything where there is nothing connected..

Ground bounce is artefact of PCB layout and probing technique...

So I would suggest to change misleading (wrong) title..

calvingloster:
Thanks for the reply much appreciated. So is this an artifact of measurement or is it inherently in the circuit itself? If it's only showing up on the ossciloscope because of leads and it's not actually causing havoc in the circuit then I don't mind.
I just need the circuit to be as noise free as possible.

The ADC will be on an analog board recieving a differential signal from a femto bias current op amp thats measuring tunneling current of a Scanning tunneling microscope so having this bounce is def going to slow the scanning speed down somewhat if it is actually something inherent to the circuit. Is this ADC not suitable because it has such fast rise and fall time?

BillyO:

--- Quote from: calvingloster on June 20, 2023, 12:36:30 pm ---I am using a microcontroller to get an ADC reading from a 16 bit ADC (LTC2326). The SPI clock speed is set to 500KHZ and im getting massive ringing on the clock, MOSI and MISO lines. this ringing seems to be showing up on channel two which is what I'm using to trigger on. I have added 50 ohm resistors in series to try damp the lines but the ringing and crosstalk is still showing up quite significantly. Is there something wrong with my scope? I tried using a 10X probe on channel two and the crosstalk gets worse.

The setup is on a breadboard and I've tried to keep channel 1 and channel 2 leads separated as much as I can. Ive added a screenshot.

Could there be something wrong with my scope?

--- End quote ---

This may not be a great image of what you are talking about, but I don't see anything of concern in it.

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