ADC08DJ3200: Noisy spikes appear in the signal

Emir Karamehmedovic

Part Number: ADC08DJ3200
Other Parts Discussed in Thread: TSW14J57EVM

Hi TI,

I use ADC08DJ3200EVM (together with TSW14J57EVM to capture data). I use single channel (A) differential signal coupled through 100nF DC blocking capacitors. Everything works well, but I get spikes in the signal that can sometimes confuse data processing. Typical spikes are shown in the figures below. What could be the cause of this? When I look at the same signal on a scope, there are no such spikes.

over 1 year ago

0 Neeraj Gill over 1 year ago

TI__Mastermind 20541 points

Hi Emir,

Are you using the ADC in background calibration mode? Or are you using it with foreground calibration mode?

Regards,

Neeraj

0 Emir Karamehmedovic over 1 year ago in reply to Neeraj Gill

Prodigy 100 points

I use foreground calibration.

0 Neeraj Gill over 1 year ago in reply to Emir Karamehmedovic

TI__Mastermind 20541 points

Emir,

Can you please provide the JMODE and sampling frequency. Can you also share the data set with good and bad data.

Regards,

Neeraj

0 Emir Karamehmedovic over 1 year ago in reply to Neeraj Gill

Prodigy 100 points

JMODE5 is used and sampling frequency is 3200MHz (6400MHz in TSW)

0 Emir Karamehmedovic over 1 year ago in reply to Neeraj Gill

Prodigy 100 points

Hi Neeraj, do you think this may be due to use on inadequate dc blocking caps? Which type and capacitance would you recommend?

0 Neeraj Gill over 1 year ago in reply to Emir Karamehmedovic

TI__Mastermind 20541 points

Hi Emir,

If you are using the EVM with default caps through the Balun. I don't expect this issue. can you try to reduce the sampling frequency to half and see if the errors still occur.

Regards,

Neeraj

0 Emir Karamehmedovic over 1 year ago in reply to Neeraj Gill

Prodigy 100 points

No, I have differential signal, so I removed resistors that couple SE signal through the balun to ADC inputs, and mounted the capacitors myself to connect the differential input SMAs to the ADC. But I will try sampling with a different frquency.

0 Emir Karamehmedovic over 1 year ago in reply to Neeraj Gill

Prodigy 100 points

I reduced the sampling frequency and the noise/glitches are still there.

0 Neeraj Gill over 1 year ago in reply to Emir Karamehmedovic

TI__Mastermind 20541 points

Hi Emir,

Are you seeing the spikes with input a signal into the ADC? What type of input signal are you feeding into the ADC?

Regards,

Neeraj

Data converters

Data converters forum

ADC08DJ3200: Noisy spikes appear in the signal