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Published byCornelius Harmon Modified over 9 years ago
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Characterization of 1.2GHz Phase Locked Loops and Voltage Controlled Oscillators in a Total Dose Radiation Environment Martin Vandepas, Kerem Ok, Anantha Nag Nemmani, Merrick Brownlee, Kartikeya Mayaram, Un-Ku Moon Oregon State University Department of Electrical and Computer Engineering MAPLD 2005 September 7-9, 2005
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Outline Test chip description Radiation test setup Results Conclusion
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Test Chip (Honeywell MOI-5)
PLLs LC oscillator PLL Ring oscillator PLL LC oscillators NMOS current source PMOS current source Complementary current source Ring oscillators Maneatis delay cell Linear-load modified Maneatis delay cell Lee-Kim delay cell
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Test Chip Die Photo LC oscillators Ring oscillators LC PLL Ring PLL
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Prototype PLLs Ring-VCO PLL LC-VCO PLL Programmable “N” & “ICP”
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Honeywell MOI-5 0.35µm process 25 (8 inputs, 7 outputs, 10 power)
Prototype PLL Summary Ring-oscillator PLL LC-tank PLL VCO tuning range 0.43GHz – 1.12GHz 1.2GHz – 1.45GHz (simulated) Power consumption 26mW @ 800MHz 35 mW @ 1.2GHz Layout area 600mm × 500mm 1000mm × 1100mm Process Honeywell MOI µm process Total pin count 25 (8 inputs, 7 outputs, 10 power)
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Complementary current sources
Prototype LC VCOs NMOS current source PMOS current source Complementary current sources
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Prototype Ring Oscillators
Maneatis cell Linear-load Lee/Kim cell Maneatis delay cell: symmetric & linear loads Lee/Kim delay cell: traditional & signal-delay-optimized layout Body ties in SOI: with body ties & without (floating body)
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Radiation Test Setup Two tests
500krad(SiO2) at a dose rate of 500 rad/sec One exposure Characterize the oscillators before and after the dose 25krad(SiO2) to 6.4Mrad(SiO2) doubling dosage each step Tested current and lock range of ring PLL vs. total radiation dose Quantify effect of annealing 35 days after radiation at room temperature
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Radiation Equipment at AFRL
Phillips low energy X-Ray (LEXR) tube Shown with cryo chamber (not used) Chip irradiated directly with IC lid removed All circuits biased except buffers
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First Test Current consumption about constant throughout irradiation
Suggests leakage current is not significant for the given dose One notable observation Shifted tuning range for ring-based oscillators Annealing until measurement of VCOs Dependence on process makes characterization of annealing difficult
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PMOS Source LC VCO
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NMOS Source LC VCO
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Complementary Source LC VCO
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Lee/Kim Traditional Layout
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Lee/Kim Signal-Path-Optimized Layout
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Linear-Load Modified-Maneatis Oscillator
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Period Jitter: LC VCOs CHIP 1 PRE-Radiation RMS (ps) Peak-to-peak (ps)
Power (mW) Frequency (MHz) PMOS Source Body Tied 2.75 18.90 29.4 1500 PMOS Source Floating Body 3.00 21.72 28.1 NMOS Source Body Tied 3.14 21.73 28.3 NMOS Source Floating Body - Complementary Body Tied 3.30 22.58 46.13 Complementary Floating Body
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Period Jitter: Ring VCOs
CHIP PRE-Radiation RMS (ps) Peak-to-peak (ps) Power (mW) Frequency (MHz) Lee/Kim Traditional Body Tied 2.59 16.79 26.90 800 Lee/Kim Traditional Floating Body 2.58 16.49 26.40 Lee/Kim Optimized Body Tied 2.40 15.86 23.43 Lee/Kim Optimized Floating Body 2.68 17.80 21.45 Linear-Load (Maneatis) Body Tied 2.79 19.52 102 1200 Linear-Load (Maneatis) Floating 3.38 22.31
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Period Jitter: LC VCOs CHIP 2 POST-Radiation RMS (ps)
Peak-to-peak (ps) Power (mW) Frequency (MHz) PMOS Source Body Tied 3.25 21.08 26.67 1500 PMOS Source Floating Body 3.05 26.90 NMOS Source Body Tied 3.30 26.13 27.92 NMOS Source Floating Body 3.07 20.00 27.69 Complementary Body Tied 3.29 22.34 37.95 Complementary Floating Body 2.94 17.89
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Period Jitter: Ring VCOs
CHIP POST-Radiation RMS (ps) Peak-to-peak (ps) Power (mW) Frequency (MHz) Lee/Kim Traditional Body Tied 3.13 21.92 26.40 800 Lee/Kim Traditional Floating Body 2.74 17.80 26.70 Lee/Kim Symmetric Body Tied 2.53 18.00 22.77 Lee/Kim Symmetric Floating Body 2.91 19.68 21.78 Linear-Load (Maneatis) Body Tied 5.27 37.03 100 1200 Linear-Load (Maneatis) Floating 6.01 40.70 99
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Second Test – Ring PLL Circuit current vs. total dose
Very little annealing After 35 days annealing
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Second Test – Ring PLL Lock range vs. total dose
Still locks at 6.2MRad(SiO2) Gaps are due to test setup After 35 days annealing
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Total Dose Effect on PLLs
Digital blocks Can tolerate large shifts in threshold voltages Immune to large doses of radiation Continue functioning until transistors cannot be turned on Charge Pump and Loop Filter Performance degradation Current mismatch & leakage Eventual functional failure VCO Tuning curve (fOSC, KVCO) changes
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Total Dose Hardening Self calibration/tuning
Analog tuning mechanisms are susceptible to total dose Digital blocks can inherently resist large doses of radiation before functional failure All digital PLLs ideal for total dosage hardening Architectures with loop parameters independent of environment
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Conclusions Analog PLL’s can be sensitive to total dose radiation
Designing with threshold shifts in mind can harden them New all-digital PLL techniques may present total dose hardened by design PLLs
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Acknowledgment We would like to thank Ken Merkel, Steve Clark, Dave Alexander, and Bill Kemp of the Air Force Research Lab in Albuquerque, NM for their direct support of the radiation testing Thanks to AFRL for sponsoring this project
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