Bigga, A

Bonna, G

Duperray, R P

Faccio, F

Glaser, M

Imbruglia, A

Jarron, Pierre

Roberts, B

CERN Document Server

5th workshop on electronic for LHC experimentsSnowmass (Colorado), 20 - 25 september 1998A RADIATION-HARDENED LOW-DROPOUT VOLTAGE REGULATORFOR LHC AND SPACE APPLICATIONS.G. Bonna(1), A. Imbruglia (1), H. Duperray (3), P. Jarron (2), F. Faccio (2), A. Bigga (2),M. Glaser (2), B. Roberts (2)(1) STMicroelectronics, Catane, Italy(2) CERN Geneva, Switzerland(3)  STMicroelectronics, Rennes, France 1. AbstractIn the LHC experiments, standard voltage regulators are placed in the dete-ctor or in the experimental hall and have to function in a challenging radiationenvironment. At present, there is not radiation-hardened low-dropout voltageregulator available hardened to total dose and displacement damage. Chargedhardrons and neutrons dominate the LHC environment and such particles inducedisplacement damage in semiconductors severely deteriorating in such a way theperformances of voltage regulators manufactured in lightly-doped high-voltagebipolar technologies. In addition total ionizing dose effects contribute to the per-formances deterioration in a way that is difficult to quantify experimentally dueto the presence of Low Dose Rate Effects (LDRE). Based on a previous study ofa bipolar radiation-hardened technology presented at the LEB conference inRome in 1998, a radiation-hardened voltage-regulator has been developed bySTMicroelectronics under a CERN RD49 contract. Specifications, performancesand radiation response to total dose, neutrons and protons are presented.2. Device outlineDuring the last two years at STMicroelectronics Laboratories of Catane theelementary structures of a ST proprietary technology, RHBip1, have been evalu-ated in its ability at working under irradiation and upgraded. The most relevantresults have been presented at the 4th workshop in Rome last year [1]. A qua-litative sinthesys is shown in fig.1.1Following the outcomes concerning Total Dose Effects (TDE), Low-DoseRate Effects (LDRE) and Neutrons, a radiation-hardened voltage regulator ableto operate in LHC and Space applications has been developed. The initial targetwas that of getting a device still able to work after an exposure to a radiationdose of 500 krad with a degradation of the performances of no more than 30 per-cent compared to the pre-rad condition.Fig 2 shows an overview of the block schematic.Apart from the circuitry usually implemented (feedback regulationloop, thermal and current limit protection, internal voltage reference) itincludes among other an overcurrent monitor. This latter operates under130100 uApre-rad10 krad100 krad500 krad    Irradiation results concerningNPN bipolar of the RHBip1 70100 uA    Irradiation results concerningPNP bipolar of the RHBip1HfeHfeFIG.1erroramplif.shutdowncurrentlimitantisat.driverON/OFFfig.2: basic block schematic of the regulatorVIN1T4II3(currentsense)alla current limitRspowerovercurrentmonitorbandgapthermalGNDSH_CNTRL    OCMINHIBITOUTPUTSENSE2the control of the current limit section giving on the pin OCM a voltagelevel of 0.4 volts whenever this protection intervenes at limiting the cur-rent at the OUTPUT pin. Being the OCM pulled-up by an internal resistorto VIN, under normal operating conditions the relative voltage levels areconcident.Others features are:.possibility of adjusting the short circuit current within 30 % of its typicalvalue by placing an external resistor between the SH_CNTRL and VINpins;.a remote sensing, allowing the regulator to function with an the outputload far from it;.possibility of controlling the OFF/ON switching of the device trough anINHIBIT pin.Even if the general architecture is basically similar to that of a conventio-nal linear regulator, each block has been designed in order to minimize asmuch as possible the performances degradation under radiation operation.This has been achieved by making use of proper rules during both theschematic and the layout phases, some of them coming from the experi-mental issues told before and others are in ST proprietary know-how inrad-hard design practice..An overview of the main target specifications is given in fig. 3.33. Characterization tests results.Some of the tests have been performed at CERN laboratories in Geneve.Up to now the responses in terms of line and load regulation have beenchecked by using the following radiations sources:.Co-60 up to 1.3 Mrad at ESA-ESTEC.total dose by X-ray 10 KeV up to 4 Mrad.neutron fluence up to 1013 n/cm2.proton fluence up to 5 x 1013 p/cm2A selection among the most significant results is presented at page 6. Allvalues on y-axis are expressed in percent units with respect to the nominaloutput voltage.Parameter                                      Test conditions                         Min.          Typ        Max   UnitOutput voltage accuracy (Vo)          Iout=5mA,Operating input voltage (Vin)    Io=3A                                         1.25                            9.7       VCurrent Limit                              Adjustable                                   1                             4.5        A                                                        Vin=Vout+2                -2              2         %                                                from 1 to 4.5 ALine regulation                          Vo+1<Vin<12V                                                 1                      %Load regulation                         5mA <Iout<3A, Vin=Vo+1                                 2                     %Quiescent current (Iq)                Vo+2.3<Vin<12,  Iout = 0 mA                         2 m                  A                                                                     Iout= 3 A                                      50 m    200m     A                                                    Vin=Vo+2, OFF mode                                    50u                   ASVR                                            Vin=Vo+2, Io=5mA f=120 Hz                        60                    dBDropout voltage                        Io=1A                                                               0.5                    V           Io=3 A                                                             1.5                    V                                                                                      f=33   Khz                     30                    dBInhibit voltage (OFF mode)   2   VInhibit voltage (ON mode)                           0.8   VInhibit input current             10u    AOutput impedance                      100 mA DC; 20 mA rms             100m OhmsOutput noise voltage   400u                  VrmsFIG. 34Others measurements have also been done at ST Catane. They are not setout in this paper because of no concern for an evaluation of the responseunder radiation.4. ConclusionSo far this first study has demonstrated that this regulators is radiation-hard, as it was designed to be. It survived protons, neutrons and gammarays with few changes of their line and load regulation graphs. Furtherstudy will be done for various biasing conditions, in order to check thevariation of other important parameters such as dropout voltage and outputnoise voltage. Finally, another important investigation will be pursued todifferent fabrication lots for a quantitative analysis of the parametersspreading.References:[1] S. Caruso and others - “RHBip1 evaluation to total dose, Low Doserate and Neutrons for a voltage regulator applications for LHC experi-ments.” - paper presented at 4th workshop on electr. for LHC experim.,Rome, 1998.50 1 2-0.1-0.2-0.3-0.4-0.5-0.60 1 2-0.1-0.2-0.3-0.4-0.5-0.6Load regulation before radiation Load regulation after 3.9 Mrad x-rays0 1 2-0.1-0.2-0.3-0.4-0.5-0.60 1 2-0.1-0.2-0.3-0.4-0.5-0.6Load regulation after 1013 neut./cm2 Load regulation after 1013 prot/cm20  1  0  -1 -2 -3Line regulation after 3.9Mrad x-raysLine regulation before irradiation           6 6 12  1  0  -1 -2 -3Iload=0 AIload=0.5A12           6 12Line regulation after 1013 neut./cm2           6  1  0  -1 -2 -312Iload=0 AIload=0.5ALine regulation after 1013 prot./cm20-1-2-316

A radiation-hardened low-dropout voltage regulator for LHC and space applications

A radiation-hardened low-dropout voltage regulator for LHC and space applications

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