System o verview Place in signal chain The amplifier chassis Provides power to the MPMT transimpedance amplifier TIA in the tunnel Conditions the signal for the ADC MPMT 12V supply ID: 1006477
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1. MPMT power supply + signal conditioner
2. System overview – Place in signal chainThe amplifier chassis:Provides power to the MPMT transimpedance amplifier (TIA) in the tunnelConditions the signal for the ADCMPMT:±12V supply0-xV (depends on beam) signalADC:±0.5V 50Ω input5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner2
3. System overview - ChassisIn the chassis:2 PCBs±12-15V power supply (MPMT)±5V power supply (PCBs)Cables + connectorsNumber of chassis (2 channels each):PSB: 8x MPMT @ 1 location: 4 chassisPS: 5x MPMT @ 1 location: 3 chassisSPS: 4x MPMT @ 2 locations: 2 chassisLHC: 2x MPMT @ 2 locations: 2 chassisTotal: 11 chassis = 22 boards + spares5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner3
4. MPMT – Circuit4x PMTs with filters: 100/25/5/1%TIA gain: 500Ω1000x + 50Ω output5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner460-200m cable
5. MPMT – PerformanceTIA needs ~7ns to settle (ringing)Parasitic capacitance might take care of that (0.25pF)THS3001: 420 MHz GBWP (190MHz here)Performance at limits for 1mA/3ns pulses5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner5
6. Simulation: CableUsing JL Sirvent’s modelAccurate model with high-frequency effectsCable length ranges from 60-200m2.5V signal results in 2.4-1.8V96-72% of original signalNote difference in shape5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner6
7. PCB overviewFeatures:MPMT power supply with filtering, reverse polarity protection, resettable fuses and voltage monitoring.DAC to generate offset for signal.Isolated I2C communications for monitor + DAC.4 signal conditioners + 1 OASIS channel.50 Ω in (CK50→SMA) / 50 Ω out (SMA)±0.5V out for ADC5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner7
8. Antialiasing filter250 MHz non-reflective low-pass filterPassive, reasonably compactMight be better to place it before the amplifier?Cable already filters somewhat5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner8
9. Simulation: ClampingValues calculated for 5mA pulse:Will saturate the ADC with the full 10mA pulseProtection Schottky diodes at outputOutput signal is clamped at ~±.7VCan tweak the clamp voltageLittle to no effect on nominal ±0.5V signal5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner9
10. Signal conditioning – optionsFixed gainVariable gainProgrammable gain5/14/2020Presenter | Presentation Title10
11. Signal conditioning – fixed amplificationTopology: Inverting amplifier with offsetAllows for attenuation or amplification: flexibleInput impedance is not as easy to control as non-inverting amplifierPlus: Current-feedback opamp = low resistancesOffset is affected by amplificationGain:0-0.5V in (1mA * 500Ω TIA)±0.5V out (inverted)Fixed gain for fewer settings to manageCan set gain so the highest PMT saturates5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner11
12. Signal conditioning – programmable amplificationTopology: Differential amplifier + offsetFixed input impedanceDiscrete steps (6 bits) – potentially more stableGain:-11.5 to +20dB (0.25 to 10x) in 0.5dB incrementsOffset stage independent, can add gainGain control can be “hidden”Highest performance – to be checked:Requires some extra partsDesigned for balanced AC in, can work here as wellTI PGA870 + THS32175/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner12THS3217 only
13. Signal conditioning – Variable amplificationTopology: Differential amplifier + offsetFixed input impedanceContinuously variable gainGain:40dB (100x): set maximum gain and attenuate itOffset dependant of gainGain control can be “hidden”Comparable to TIA:Similar rise time (slightly faster)Needs another DAC for gainTI VCA821/VCA8245/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner13
14. Several possibilities:Send buffered signal directly from the input (after filter if fitted?)Send conditioned ±0.5V signalCondition signal separatelyOASIS5/14/2020Presenter | Presentation Title14
15. See PDFPreliminary layoutSchematics5/14/2020Miguel Martin Nieto | MPMT power supply + signal conditioner15