TA11-370: A 2.56 GHz Radiation Hardened Fractional-N Sub-sampling All-Digital Phase-Locked Loop

https://radnext.web.cern.ch/ https://www.linkedin.com/company/radnext EDMS NO. 3355734 VALIDITY Released REV. 1.0 DOI: 10.5281/zenodo.17288030 RADNEXT Transnational Access Summary Report Project title A 2.56 GHz Radiation Hardened Fractional-N Sub-sampling AllDigital Phase-Locked Loop Project TA identifier TA11-370 General application High-energy accelerators Type of test SEE Group leader, Institute Paul Leroux, KU Leuven Co-authors, Institutes Jeffrey Prinzie, KU Leuven Qichao Ma, KU Leuven Date(s) of the experiment 16th May, 2025 Facility RADiation Effects Facility, University of Jyväskylä Amount of access granted 6 h Objectives of the experiments The goal of this project is to study the radiation performance of the proposed fractional-N Subsampling ADPLL and to verify whether our radiation-hardened-by-design technique can enhance its radiation tolerance. 1. Verifying the effectiveness of the TMR strategy. 2. Testing the SEE cross section of the DTC, which can cause faulty Bang-Bang Phase Detector (BBPD) outputs. A heavy ion test will determine if such disturbances affect SSADPLL operation. 3. Building on our previous work, which demonstrated that the fast recovery algorithm can mitigate disturbances from SEEs in the inductor of an integer ADPLL [2], we will now verify this algorithm in the fractional-N SSADPLL. This structured approach will provide insights into potential improvements and validate the robustness of our radiation-hardened techniques. Experiment test report The ADPLL configured in three different modes was exposed to three different ions (Xe, Kr, and Ar) with Linear Energy Transfer (LET) values ranging from 58.5 MeVcm2/mg to 9.7 MeVcm2/mg. For each ion, a fluence of 1.5×106 ions/cm2 and a flux of 1000 ions/cm2/s was achieved for each ADPLL configuration. The tests were conducted in air mode without tilting. During the test, A 40-MHz clock provided from a SKYWORKS SI570-PROG-EVB board was employed EDMS 3355734 v.1 status In Work access Restricted PDF from TA11-370-Zenodo.doc modified 2025-10-07 16:07 https://radnext.web.cern.ch/ https://www.linkedin.com/company/radnext EDMS NO. 3355734 VALIDITY Released REV. 1.0 as the reference clock. Different configurations including loop gain, switching time for each bandwidth level and the threshold to trigger the fast recovery can be set through SPI. The ADPLL operated at 2.56 GHz with a prescaler of 2 at the output of DCO, yielding an output frequency of 1.28 GHz. To measure the ADPLL output frequency, it is firstly down-converted to 25 kHz and then sampled with a sampling rate of 5 MHz by an NI USRP-2900 Software-Defined Radio (SDR). The ADPLL was configured in closed loop with three different ions (Xe,Kr and Ar) to study if the SEEs cross section has increased significantly compared with our previous integer ADPLL. The cross section of the test results are shown in figures below. The cross section of this fractional-N ADPLL was compared with that of the previous integer ADPLL, as shown below. The cross section of the fractional-N ADPLL is much higher than that of the integer ADPLL. This unexpected result may be due to the different cocktails used during the two tests. Further analysis is ongoing to determine the reason for this difference. https://radnext.web.cern.ch/ https://www.linkedin.com/company/radnext EDMS NO. 3355734 VALIDITY Released REV. 1.0 Outcome of the experiments Please indicate what the experiment is likely to lead to by putting an ‘X’ next to one or more of the possible outcomes below. Journal publication X Data for Thesis Follow-up experiment at same facility Follow-up experiment at another facility Other As a RADNEXT user, we encourage you to submit the scientific results of your experiments to journals as well as to the NSREC and RADECS data workshops. Please remember to include the RADNEXT acknowledgment into your publications! RADNEXT acknowledgment: This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 101008126.