ADS54J60EVM: Count spikes appear on histogram every 3 or so bins

Danilo A.

Part Number: ADS54J60EVM
Other Parts Discussed in Thread: ADS54J60

Hi Team,

Our customer is using ADS54J60EVM and TSW14J56 to analyze the electrical noise of 1GHz photodetector. When plotting the histogram they've noticed that the histogram is off as it seems that there's a spike in the number of counts every 3 or so bins. This also happens when no input is applied (as can be seen in the respective figures). He tried freezing the offset correction function, and this sometimes appears to solve the problem. However, the behavior remains inconsistent both in time, with consecutive acquisitions showing different behaviors, but also across channels.

No input applied (Good Histogram)

No input applied (Bad Histogram)

Bad histogram

Bad histogram in the next acquisition

Is this behavior expected?

Thank you for your support!

Regards,

Danilo

over 4 years ago

0 jim s over 4 years ago

TI__Guru* 91947 points

Danilo,

Try the steps in the attached document. Was the EVM modified? What mode are they operating in?

Regards,

Jim

ADS54J60_OS_IL_freeze.pptx

0 Danilo A. over 4 years ago in reply to jim s

TI__Mastermind 28720 points

Hi Jim,

Thank you for your response. According to the customer,

We have not modified the EVM, and I am using the default scripts (ADS54J60_LMF_8224.cfg and LMK_Config_Onboard_983p04_MSPS.cfg). Using the ADS54Jxx GUI, I have frozen the IL engine, and DC offset correction block without input signal, as described, but obtained inconsistent results. Is the 500ms wait time a strict condition, or could there be a longer delay?
After changing the DC bandwidth, while the DC block is unfrozen, the histogram continues to oscillate between having and not having spikes. I have only been able to consistently fix the issue by motoring both channels while the DC offset is unfrozen and only freezing when the histogram momentarily improves (as shown in the attached file). After this, the behavior is consistent over time.

Regards,

Danilo

0 jim s over 4 years ago in reply to Danilo A.

TI__Guru* 91947 points

Danilo,

I am consulting with the deign team about this.

Regards,

Jim

0 jim s over 4 years ago in reply to jim s

TI__Guru* 91947 points

Danilo,

How much current is each 5V source able to provide to the two boards? Make sure they can provide at least 3A for the ADC board and 4A for the TSW board. Are you pressing the ADC reset on the ADS54J60EVM after loading the LMK file?

Regards,

Jim

0 Danilo A. over 4 years ago in reply to jim s

TI__Mastermind 28720 points

Hi Jim,

According to the customer, both adapters are able to supply 4A to the boards. He is also pressing the reset button after loading the LMK file as specified in the ADS64J60EVM User's Guide.

Regards,

Danilo

0 jim s over 4 years ago in reply to Danilo A.

TI__Guru* 91947 points

Danilo,

Please have the customer try the two attached configuration files to see if they help.

Regards,

Jim

ADS54J60_LMF_8224_A.cfg ADS54J60_LMF_8224_B.cfg

Data converters

Data converters forum

ADS54J60EVM: Count spikes appear on histogram every 3 or so bins