1. Stan Durkin CMS Upgrade Week 1 A Digital Pipelined Cathode Front End Board (DCFEB) Stan Durkin The Ohio State University

2. Stan Durkin CMS Upgrade Week 2 Present Cathode Front End Board (CFEB) BUCKEYE (ASIC) - amplifies and shapes input pulse SCA (ASIC) - analog storage for 20 MHz sampled input pulse ADC - events with LVL1ACC digitized and sent to DAQ Motherboard (25 nsec/word) Controller FPGA - controls SCA storage and digitization Comparator ASIC - generates trigger hit primitives from shaped pulse Input/Output - 5 cfebs/chamber, 96 strips/cfeb - 96 switch capacitors/channel - system is self triggering Optimized for Precision Position Measurement

3. Stan Durkin CMS Upgrade Week 3 - 6 Buckeyes serve 6 planes x 16 strips - 6 SCA’s serve 96 strips with 96 caps each 50 nsec/sampling no pedestals (< 1%) -6 ADC’s (150 nsec digitization) 12-bit + overflow bit output 1 strip charge/25 nsec 8 samples digitized for each of 96 strips -6 SCA’s (96 caps/strip) LVDS signaling no cap pedestals -Control FPGA 12 blocks of 8 caps each grey-code (1 bit flip) addressing (see movie for algorithm) 16 Cap Delay Cap Storage (Poisson) Cap Digization (Queue) Beam CrossingPreLCTL1A·LCT 0.8  sec2.2  sec 26  sec Caps can be used for storage when all others in use 16 caps set aside for possible use For L1A  LCT use LCT to choose which 8 capacitors to digitize Done CFEB 50 nsec Sampling and Digitization Each Strip Amplifier Charge stored every 50 nsec in capacitors

4. Stan Durkin CMS Upgrade Week 4 Simulation Single Strip Capacitor Usage A Nontrivial FPGA Algorithm 8 capacitors/block Green – recently used Blue – set aside waiting for L1A Red- digitizing

5. Stan Durkin CMS Upgrade Week 5 16 Cap Delay Cap Storage (Poisson)Cap Digization (Queue) Beam CrossingLCTL1A·LCT 0.8  sec2.2  sec 26  sec Transfer to DMB Complete Caps can be used for storage when all others in use For SLHC this is the main capacitor usage Data Bottlenecks in CSC DAQ at SLHC CFEB’s 96 Capacitors/channel is main DAQ rate limiter DCC’s SLINK-64 is second DAQ rate limiter (configurable) Simple Model CFEB Capacitor Storage

6. Stan Durkin CMS Upgrade Week 6 Strip Channels Time (50ns/bin) Neutron/Gamma Event from X5 Beam test (Aug 99) Random coincidence between L1A and Neutron/Gamma Background Dominates Rate

7. Stan Durkin CMS Upgrade Week 7 SCA Occupancy: LHC Rate Assumptions L1 Accept: 100 kHz LCT rate: 69 kHz per CFEB (worst case – ME1/1) Estimated LCT rate for 10**34 lumi (D. Acosta et al, 2001) Chamber Type LCT rate per CFEB (kHz) ME1/1 69 ME1/2 4 ME1/3 2 ME2/1 21 ME2/2 3 ME3/1 11 ME3/2 2 ME4/1 8 ME4/2 9 L1-LCT coincidence rate per CFEB: 100 kHz x 70 kHz x 75 ns = 0.5 kH Digitization time (with 6 ADCs on each CFEB) 16 channels x 16 samples/channel x 100 ns = 26  s Note: This is Monte Carlo, We haven’t measure rates yet! Problem! ‘ME1/1 LCT 96kHz/chamber (20 kHz) CMS Note 2002-007’ Hauser

8. Stan Durkin CMS Upgrade Week 8 ME1/1 Effective SCA Buffer Occupancy at SLHC At SLHC: use same L1 accept rate assuming rates go up linearly. Maximum LCT rate is 700 kHz (ME1/1), L1-LCT match rate is 5.25 kHz. Average number of LCTs during 5.2  s (=6  s-0.8  s) holding time for 2-blocks:  =5.2x10 -6 x700x10 3 =3.64 Average number of L1-LCT matches during 26  s digitization time:  =26x10 -6 x5.25x10 3 =0.1365 Probability of overuse of SCA: 0.09 !!!!!!!!!

9. Stan Durkin CMS Upgrade Week 9 Digital CFEB – A Nice Idea for the SLHC Replace Conventional ADC and SCA storage with Flash ADC and Digital Storage New System Deadtimeless, Removes rate worries Similar cost to old system Fairly Radical Design – Couldn’t build 8 Years Ago

10. Stan Durkin CMS Upgrade Week 10 Fix ME1/1 Ganged Strips Removes ganged strips in ME1/1a (aka ME1/4) Gets rid of ghost tracks trigger and offline software Requires 7 DCFEBs per ME1/1 Chamber Cathode charges Improve Cathode Trigger Primitives -presently an ASIC chip -do digitally on new board  =1.5  =2.0  =2.4 Besides Deadtimeless there are other Advantages

11. Stan Durkin CMS Upgrade Week 11 Overall Scope of Upgrade ME1/1 Electronics Upgrade 504 DCFEBs 72 DMBs 72 TMB (d.c.) 12 MPC 72 LVDB (+more power) 72 LVMB 1008 Cables (default skewclear) LVDB

12. Stan Durkin CMS Upgrade Week 12 Evaluation of Flash ADCs (B. Bylsma O.S.U) ADC choices:(8 ch, 12 bit, 20-65 MSPS, Serial LVDS output)  MAX1437 (Maxim) 1.8V supply, 1.4V pp range  ADC12EU050 (National) 1.2V supply, 2.1V pp range  AD9222 (Analog Devices) 1.8V supply, 2V pp range  ADS5281 (Texas Instr.) 3.3V analog, 1.8V digital, 2V pp range

13. Stan Durkin CMS Upgrade Week 13 No Flash ADC is a drop-in replacements for SCA/ADC -ADC’s  All have differential inputs  Limits on common mode  Have internal input bias network -Pre-Amp  Single ended output  Limited range of baseline level  Designed to drive small capacitive load -Pre-Amp/ADC Interface  Mnfr. suggest transformer coupling (not an option for us)  Amplifier to generate differential signal (requires 96 amplifiers)  Direct couple single ended signal (common mode consequences) (level shifting/scaling)  AC couple single ended signal (common mode consequences) (no level shifting, but still have biasing to consider Flash ADC/Amplifier Coupling Issues

14. Stan Durkin CMS Upgrade Week 14 Common Mode Constraints (ADS5281) ADC Constraints:  V cm -600mV < (IN+ + IN-)/2 < V cm +300mV (1.8V pp on IN+)  (IN- -1V) < IN+ < (IN-+1V) (ADC output range) Pre-Amp Constraints:  Baseline Level -Currently 1.8V -Max ~2.0V -Min ~1.2V (maybe 1.0V)  Drive Capability -Small (few mA at best) Scaling:  Scale down input  Add digital gain on output  Resistor divider Direct Coupling Difficult Common Mode  Data Sheet: V cm = 1.5  V  How far from nominal?  Baseline Level -Range  Digital output range is 2V  But is linear range of common mode 2V

15. Stan Durkin CMS Upgrade Week 15 DCFEB R&D plans Short Term Goal: Install Prototype System on a ME4/2 Chamber during 2012 Shutdown DCFEB Critical Item so Divide Labor (Generic R&D) DCFEB R&D Board, OSU FPGA Firmware, Florida Virtex 6 R&D Board, TAMU Virtex 6 Radiation Testing, NEU Optical Cable Interface DCFEB  DMB/TMB 50 nsec Samples Buckeye Amp -> ADC5281 Evaluation Board Preliminary Tests are Encouraging Flash ADC sensitive to common mode gain Need R&D board to fully test coupling and noise

16. Stan Durkin CMS Upgrade Week 16 DCFEB R&D Board Designed to study (there will be issues): - Coupling single ended Buckeye Amp to bipolar flash SCAs - Linearity/Shape … Noise on Analog-Digital boards can be problems - use old PC board’s analog isolation

17. Stan Durkin CMS Upgrade Week 17 DCFEB R&D Board Available Late this Summer Then: - noise tests - linearity/pulse shape tests - radiation tests, SEU and lifetime measurements If all goes well layout and schematics of a DCFEB Prototype board will start late Fall Conclusions