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Design Techniques for Radiation Hardened Phase Locked Loops

Proportional. Control word. Integral gain. TDC Output. Normalizing gain. Design Techniques for Radiation Hardened Phase Locked Loops. Anantha Nag Nemmani, Martin Vandepas, Kerem Ok, Kartikeya Mayaram and Un-Ku Moon Oregon State University Electrical Engineering and Computer Science.

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Design Techniques for Radiation Hardened Phase Locked Loops

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  1. Proportional Control word Integral gain TDC Output Normalizing gain Design Techniques for Radiation Hardened Phase Locked Loops Anantha Nag Nemmani, Martin Vandepas, Kerem Ok, Kartikeya Mayaram and Un-Ku Moon Oregon State University Electrical Engineering and Computer Science 2005 MAPLD International Conference ◊ Ronald Reagan Building and International Trade Center Washington, D.C. ◊ September 7-9, 2005 Effects Single Event Effects (SEE) Total Ionization Dose (TID) Effect on Phase Locked Loops (PLLs) SEE on PLLs • VCO tuning curves shift • Change in nominal frequency and VCO gain • Change in chargepump current • Loop parameters changed as a result • Loop transfer function altered • Accumulation of charge in gate oxide • Vth NMOS ↓ & Vth PMOS ↑ • Transient error currents • Modelled as sum of exponential current sources Digital PLL Tuning curves of Lee/Kim Ring oscillator before and after radiation. SEE on last stage of frequency divider SEE on control node Digital Loop Filter Time-to-digital converter Digitally controlled analog oscillator • Digitally controlled analog oscillator (DCAO) • Time-to-digital converter (TDC) • Digital loop filter • Exponential delay chain • Latches • Sign detection • Pseudo-thermometor encoder • Lee/Kim delay cell • Fine/Coarse tuning • Fine tuning current DAC • 6 fine bits + 6 coarse bits • Type – II loop filter Analysis Operation of a TDC Analysis Verification DCAO resolution 1. DCAO: Openloop gain For optimum performance Phase margin - ΦM Incremental phase accumulated 2. Phase detector: 3. Loop filter: CPPLL Analogy Response to frequency step at the input. Simulink Agrees with mathematical model Radiation Hardening Self-Calibration Layout Redundancy & Majority Voting Single Event Hardening • Loop parameters • fLSB & dT – Process dependent • Gn, α & β – Digital constants • Loop dynamics are dependent only dependent on: • Self calibration • Calibrate Kdig to the desired value Accumulator Time-to-digital converter Frequency Divider MAPLD 2005/228

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