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A radiation-tolerant LDO voltage regulator for HEP applications F.Faccio, P.Moreira, A.Marchioro, S.Velitchko CERN Outline Motivation Specifications Implementation Measured performance Radiation performance Conclusion Heidelberg LECC05 F.Faccio – CERN/MIC Motivation Power distribution in LHC experiments is a real challenge Need for voltage regulation close to the electronics to be powered: linear regulators are often used To limit (useless) power dissipation, LDO regulators are desired, having drop-out voltages as low as 100150mV Rad-hard regulators with these characteristics are prohibitively expensive A rad-hard LDO regulator with limited current capability (300mA) can be developed as an ASIC using “our” quarter micron CMOS process at low cost! Heidelberg LECC05 F.Faccio – CERN/MIC Specifications Min Typ Output V (V) Input V (V) Output I (mA) Max Comment 2.5 Fixed in this version 2.65 2.7 3.5 0 250 300 Dropout V (mV) 150 Quiescent I (mA) At 300mA current 1 Over-V prot. (V) 3.5 Protects regulator itself Over-I prot. (mA) 400 600 Switch to current regulation Over-T prot. (oC) 150 170 Disable in/out Heidelberg LECC05 yes F.Faccio – CERN/MIC Possible to disable, output flag Implementation (1) Regulator named “CRTREG1”, as part of the CERN Radiation Tolerant (CRT) family of components External compensation solution chosen: the dominant pole is the output pole This imposes value (min. 1, suggested 6.6mF) and characteristics (low ESR of the order of 20mOhm) of the output compensation capacitance, but allows for larger regulator bandwidth, hence good PSRR and transient response Integrated in 0.25mm CMOS technology using radiation-tolerant layout techniques Heidelberg LECC05 F.Faccio – CERN/MIC Implementation (2) Functional block diagram Vin Vout Switches for disable R1 Over-I monitor Over-V monitor off Error amplifier R2 Over-T monitor Bandgap Disable in Disable flag Heidelberg LECC05 F.Faccio – CERN/MIC Gnd Implementation (3) Chip size: 2x2mm Multiple pads for input and output current Mounted on a very compact plastic package (4.9 x 6.1 x 1.6 mm), 16L-EPP-SSOP Heidelberg LECC05 F.Faccio – CERN/MIC Measured performance Samples packaged and mounted on test boards, with different output capacitors (to test transient response) 10 samples measured Quiescent current: 800mA at Vin=2.65V; 950mA at Vin=3.3V Output noise (Cout=6.6mF), over full bandwidth: 170mV rms for I=0 530mV rms for I=250mA Heidelberg LECC05 F.Faccio – CERN/MIC CRTREG1 Cout Measured performance: line and load regulation Measurements on 10 samples Dropout at 300mA output current: average 160mV, maximum 235mV Line regulation above Vin=2.8V, for I=300mA: average 1.7mV (0.09%/V), maximum 2.5mV (0.14%/V) Load regulation from I=0 to I=300mA, for Vin=2.8V: average 14.2mV (0.0018%/mA), maximum 15.5mV (0.002%/mA) Line regulation 2.6 2.56 2.55 2.54 2.5 Iout=0A Vout (V) Vout (V) Load regulation 2.58 Iout=0.05A 2.45 Iout=0.1A 2.52 Vin=2.6V 2.5 Vin=2.65V Iout=0.15A 2.4 2.48 Iout=0.2A Vin=3.0V Iout=0.25A 2.35 Vin=2.7V 2.46 Iout=0.3A 2.3 Vin=3.5V 2.44 2.5 2.7 2.9 3.1 3.3 3.5 0 Vin (V) Heidelberg LECC05 0.05 0.1 0.15 0.2 Output current (A) F.Faccio – CERN/MIC 0.25 0.3 0.35 Measured performance: protections Over-Temperature OK: when regulator draws more than 1.8A at Vin=3.3V, it is disabled (test in temperature done by disabling Over-current protection and heating the regulator with large currents) Over-Voltage OK: when Vin is above about 3.55 V, the regulator is disabled Over-Current works but sets-in at current depending on Vin (up to 800mA). Origin understood and easy to correct. Heidelberg LECC05 F.Faccio – CERN/MIC Measured performance: line and load transients Line transients: Input voltage Output voltage 200mV/div 50mV/div Load transients: Transient of 500mV Vin At 100mA and 250mA For Cout =3.3mF and 6.6mF I=250mA, Cout=6.6mF Output voltage 100mV/div Vin=2.8V, Cout=6.6mF 250mA to 0 0 to 250mA Time 10mS/div Heidelberg LECC05 Transient from I=0 to 250mA At Vin=2.65, 2.8 and 3.3V For Cout =1mF, 3.3mF and 6.6mF Time 10mS/div F.Faccio – CERN/MIC Measured performance: PSRR Power Supply Rejection measured injecting sine wave signal at different frequency at the input (50-100mV peak-peak) Measurements for I=0 and 250mA, and for Cout=3.3mF and 6.6mF 0 -10 Vin=3V Cout=6.6mF PSSR (dB) -20 Load=0A Load=250mA -30 Able to filter effectively at full load up to 100kHz (similar regulators cut at 1kHz typically) -40 -50 -60 -70 -80 -90 1.E+00 Heidelberg LECC05 1.E+02 1.E+04 1.E+06 Frequency (Hz) F.Faccio – CERN/MIC 1.E+08 Radiation performance (1) Irradiation at IONISOS (Dagneux, F) with a 60Co source; dose rate about 200 krad/h Regulators under bias during irradiation: Vin=3V, I=0 (3 samples) and 250mA (3 samples) TID levels achieved: 1.7 Mrad – 1 sample 7.1 Mrad – 1 sample 12.4 Mrad – 2 samples 20 Mrad – 2 samples Measured performed for all samples at the end of irradiation, hence after annealing for 57-114 hours at room T and under bias Heidelberg LECC05 F.Faccio – CERN/MIC Radiation performance (2) 2.7 Main effect: output voltage shifts with TID (max 110mV after 20Mrad). This is due to shift in bandgap voltage reference. Line and load regulation do not change significantly Line regulation before (dots) and after 20Mrad (lines) 2.7 Vin=3V and 3.5V 2.65 2.65 I=0 to 300mA, step 50mA 2.6 Vin=2.7V 2.6 2.55 Vout (V) Vout (V) Load regulation before (dots) and after 20Mrad (lines) 2.5 2.45 2.55 Vin=2.65V 2.5 2.4 Vin=2.6V 2.45 2.35 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 0 Vin (V) Heidelberg LECC05 0.05 0.1 0.15 Output current (A) F.Faccio – CERN/MIC 0.2 0.25 0.3 Radiation performance summary Output voltage shifts with TID Over-voltage detection threshold shifts with TID TID effects not dependent on load condition Regulator tolerant to TID up to 20Mrad, probably more 1.7Mrd+144hours load=250mA pre-rad after rad Output voltage (V) Dropout V (mV) Line regulation (mV) I=100mA I=300mA Load regulation (mV) Vin=2.75V Vin=2.8V OverV threshold (V) Vbandgap (V) V2V5 (V) Heidelberg LECC05 7.12Mrd+117hours load=0 pre-rad after rad 12.4Mrd+96hours load=0 pre-rad after rad 20Mrd+57hours load=250mA pre-rad after rad 2.53 234 2.54 138 2.55 186 2.59 134 2.55 135 2.63 135 2.54 135 2.65 137 0.7 1.2 0.8 0.9 1.2 1 1.7 0.6 0.2 2.3 0.9 0.9 0.7 2.4 1.4 2 18.3 14.8 3.61 14.1 13.7 3.57 1.18 2.35 15.7 14.2 3.6 14.9 13.8 3.62 1.196 2.38 14.6 14.2 3.57 33 15.1 3.67 1.214 2.42 14.3 13.6 3.55 53.2 16.5 3.69 1.223 2.43 F.Faccio – CERN/MIC Conclusion CRTREG1, a compact LDO radiation-tolerant voltage regulator has been developed Its performance is well comparable to commercial LDO regulators (dropout, line and load regulation, transient response, PSSR) First prototype fully working, easy correction to be implemented for better stability of over-current protection Radiation tolerance up to 20Mrad from 60Co source has been demonstrated The regulator is ready for production Heidelberg LECC05 F.Faccio – CERN/MIC