CMS Tracker FED Front End Module Analogue Circuit

CMS Tracker FED Front End Module Analogue Circuit Considerations Draft 1. 0 Rob Halsall et al. Rutherford Appleton Laboratory Instrumentation Department 27 March 2002

Signal Ranges Opto RX Output ADC Input 1. 56 V 1. 4 V 1. 5 V Common Mode 0. 5 V 0. 4 V Opto RX Offset, 0. 2 V -> 0. 56 V 0. 2 V 0 V 0 V Limits of Opto Rx Output, assuming default opto settings - see below 1 V range of header/signal + common mode -> 10 bit, 1 m. V/bit 0. 25 V range of signal -> 8 bit, 1 m. V/bit Assume Opto Rx Offset voltage closely matched across all 12 channels Default Opto Rx Controls = 000110 Rutherford Appleton Laboratory Instrumentation Department 27 March 2002

Single Stage AD 8138 or equivalent High AC current fed back to Opto Rx Output DC Currents effecting operating point Opto Rx ouput is a current source not voltage source External resistor diff gain of 2 Gain is adjustable 2 V peak to peak mode 1500 R VD=+3. 3 V +3. 3/5 V Opto Rx 750 R + - 22 R + 10 ADC 100 R 750 R - +8138 22 R - -3. 3/5 V VD 1500 R VD/3 DAC High AC currents fed back through feedback resistors Causes Ripple Problem - couples directly to output Point needs less than half LSB ripple ~500µV Common to up to 12 channels in module Possible cross talk between channels Rutherford Appleton Laboratory Instrumentation Department 27 March 2002

Single Stage AD 8131 or equivalent High AC current fed back to Opto Rx Output DC Currents effecting operating point Opto Rx ouput is a current source not voltage source External resistor-less diff gain of 2 2 V peak to peak mode VD=+3. 3 V +3. 3/5 V Opto Rx + - 22 R + 10 ADC 100 R - +8131 22 R - -3. 3/5 V VD VD/3 DAC Ripple Problem - couples directly to output Point needs less than half LSB ripple ~500µV High AC currents fed back through feedback resistors Common to up to 12 channels in module Possible cross talk between channels Rutherford Appleton Laboratory Instrumentation Department 27 March 2002

Two Stage AD 8138 -8131 or equivalents Vout+ = Vin+ Vout- = 2 VOCM - Vin+ Resistor-less gain of -1 +3. 3/5 V Vout+ = VOCM + Vin+ Vout- = VOCM - Vin+ External resistor-less gain of 2 2 V peak to peak mode VD=+3. 3 V +3. 3/5 V - + + - 22 R + 10 ADC + -8138 Opto Rx - +8131 100 R -3. 3/5 V 22 R - -3. 3/5 V VD VD/3 DAC Driving High Impedance Inputs Common to 12 channels in module Rutherford Appleton Laboratory Instrumentation Department 27 March 2002

Two stage transfer functions example AD 8131 AD 8138 Opto Rx Output Offset of 0. 2 V Signal swing of 1 V Rutherford Appleton Laboratory ADC in 2 VPP Mode ADC Common Mode VDD/3 = 1 V Instrumentation Department 27 March 2002

Single Stage EL 2140 or equivalent External resistor- less gain of 2 2 V peak to peak mode VD=+3. 3 V + + Opto Rx 22 R + 10 ADC 100 R - -2140 22 R - -3. 3 V VD VD/3 DAC True Differential Instrumentation Amplifier 3 op-amp internal architecture - to be confirmed All Inputs High Impedance Driving High Impedance Inputs Common to 12 channels in module Rutherford Appleton Laboratory Instrumentation Department 27 March 2002

Summary Approach Amp type Amp Gain Adj Ripple Power Estimate* Cost Vendor Second Source Package Sim Model AD 8131/8 1 stage Diff Yes/No >= LSB 85 W Low/Mod Major TI µSOIC Yes AD 8131 & 8 2 Stage Diff No <<LSB 95 W High Major TI µSOIC Yes EL 2140 C 1 Stage Diff Instr No <<LSB 75 W Low Intersil No? SOIC Yes EL 2140 C - needs further study? * Estimated FED Power - still under study Rutherford Appleton Laboratory Instrumentation Department 27 March 2002

9 U Board Layout Front End Envelope 130 mm 45 mm 366. 7 mm 1 270 mm 8 Rutherford Appleton Laboratory Instrumentation Department 27 March 2002

Front End Module Layout EL 2140/XC 2 V 2000 33 x 40 mm 45 mm 27 x 27 mm FPGA XC 2 V 1000 XC 2 V 3000 FG 676 12 x 12 mm FPGA XC 2 V 40 CS 144 Opto Rx NGK 130 mm 9 x 9 mm ADC AD 9218 ST 48 5 x 3 mm DIFF OP-AMP AD 9218 RM 8 - µSOIC N. B. No Passives Shown DIFF OP-AMP EL 2140 SOIC 5 x 6 mm FPGA XC 2 V 250 FG 256 17 x 17 mm Double Sided Single Sided Rutherford Appleton Laboratory Instrumentation Department 27 March 2002