Single Event Upset Energy Dependence In a BuckConverter

Single Event Upset Energy Dependence In a Buck-Converter Power Supply Design Gary Drake, Member IEEE, James Proudfoot Argonne National Laboratory, Lemont, IL USA On Behalf of the ATLAS Tile Calorimeter System Bruce Mellado 2, Anusha Gopalakrishnan 1, Sanish Mahadik 1, Robert Reed 2, Abhirami Senthilkumaran 1 1 - University of Wisconsin-Madison, WI USA 2 – The University of the Witwatersrand, Johannesburg, SA The Tile. CAL Low Voltage System LVPS Brick • Power for Tile. CAL Front-End Electronics • Novel Switching DC-DC Power Supply LVPS Box 8 bricks per Box – Custom, Compact, High-Efficiency, 250 Watt – 8 Different Voltages Customized Bricks – Water Cooled; System Interface & Monitoring – Environment: Magnetic Field, Radiation Tolerant • 256 boxes on detector, 2048 bricks, + spares ð Reliability is Important Infrequent Access Detector Section End of Long Barrel LVPS Access on Detector Drawer Electronics We have performed a study of the susceptibility to Single Event Upsets (SEU) on the new upgraded supplies Radiation Testing Methodology 3. 78 2. 74 x 1011 6. 74 x 1010 RSHUNT - GNDPRI VIN* IIN* Run Startup Stop & Shutdown Over Temp Control • SEU Testing Program – Proton beam at Mass. Gen. Hospital – 200 Me. V protons – Read out continuously during irradiation To ELMB Test Setup Configuration Startup Shutdown (Control Interface) OVP, OCP, Temp, & Monitor + Transformer SEE Fluency (protons/cm 2) FET Driver 200 V LT 1681 Controller Chip + VPRI - Op. Amp SEC Power NIEL Fluency (neutrons/cm 2) + LC Filter Vout RSHUNT + VSEC - - GNDSEC VFB Opto Isolator TID (Grays) LC Buck VOUT* IOUT* Monitor Voltages IFB Primary Opto Isolator – 10 Years of Running, L = 1034 cm-2 sec-1 Test Setup at MGH LC Filter PRI Power • Radiation Tolerance Requirements Block Diagram of Brick Isolated Secondary Measurements & Results • 1 st Measurement – Dec. , 2010 • The Fix – Soft Start not used in brick operation – But, circuit does control startup rate ð Want capacitor for cold start ð Want capacitor out of circuit for normal operation ð Add a diode & resistor: – Bricks tripped from SEUðSEU Problem – 188 Me. V protons • 2 nd Measurement – Feb. , 2011 – Test board with individual components – 188 Me. V protons – Discovered: LT 1681 Controller Chip trips & restarts ðSoft Start Feature • 4 th Measurement – Apr. , 2012 Study SEUs as a function of energy – 60 Me. V, 80 Me. V, 100. 5 Me. V, 140 Me. V, & 216 Me. V – Results: See energy dependence Schematic Soft-start capacitor External component Value controls startup delay • Theory: Bendel Parameters [1] LT 1681 Block Diagram – Diode conducts at cold start – Diode is back biased – SEUs still happen, but recovery is fast – In general, SEU susceptibility depends on fab tech. , feature size, layout, and configuration – Bendel Parameters: Parameterization of form: –Our fit: SEMI-EMPIRICAL 2 PARAMETER FIT • 3 rd Measurement – Apr. , 2011 – Fix installed on 3 bricks – No more trips! • A Puzzle – SEUs not seen in earlier tests at 60 Me. V – Why? . . . [1] W. J. Stapor, et al. , IEEE Trans Nucl. Sci. , Vol. 37, NO. 6, pp. 1966 -1973, December 1990. Argonne National Laboratory is a U. S. Department of Energy laboratory managed by U Chicago Argonne, LLC.