9th July, 2003CMS Ecal MGPA test results1 MGPA test results first results presented 25 th June – repeat here + some new results testing begun 29 th May on bare die (packaging still underway) two chips looked at so far – both working (all results here from one only) OUTLINE introduction test setup description analogue performance gain linearity matching noise (barrel and endcap) 5 Mrads irradiation results I2C offset adjust calibration feature power consumption summary

9th July, 2003CMS Ecal MGPA test results2 MGPA target specifications ParameterBarrelEnd-Cap fullscale signal60 pC16 pC noise level10,000e (1.6 fC)3,500e (0.56 fC) input capacitance~ 200 pF~ 50 pF output signals (to match multi-channel ADC) differential 1.8 V, +/ V around Vcm = (Vdd-Vss)/2 = 1.25 V gain ranges1, 6, 12 gain tolerance (each range)+/- 10 % linearity (each range) +/- 0.1 % fullscale pulse shaping (filtering)40 nsec CR-RC channel/channel pulse shape matching < 1 % technology spec. for resistors used OK for mid and high gain ranges (low gain not a problem) OK simulation results

9th July, 2003CMS Ecal MGPA test results3 RfRf charge amp. R G1 diff. O/P stages CfCf V CM CICI RIRI transconductance gain stages RIRI DAC I2C and offset generator ext. trig. MGPA main features 3 gain channels 1:6:12 differential outputs -> multi-chan. ADC pulse shaping (external components) R f C f = 2R I C I = 40 nsec. choose R f C f for barrel/endcap calibration facility prog. amplitude (simple DAC) needs external trigger I2C interface to programme: output pedestal levels enable calibration feature cal DAC setting C CAL R G2 R G3 I/P V CM CICI RIRI RIRI CICI RIRI RIRI

9th July, 2003CMS Ecal MGPA test results4 MGPA photo die size ~ 4mm x 4mm for packaging in 100 pin TQFP I2C charge amp VI stage diff. O/P stage offset gen. hi mid lo

9th July, 2003CMS Ecal MGPA test results5 RAL test board packaged chips not yet available but RAL board can take bare die dual purpose design 1) standalone–used here 2) interface to standard DAQ system bias components fixed – no adjustment possible (without changing 0402 components) most results here for barrel feedback components to first stage (except where indicated)

9th July, 2003CMS Ecal MGPA test results6 Test setup for pulse shape measurements diff. probe or single- ended buffered signal note: very fast risetime charge injection -> pulse shape distortion on rising edge due to slew rate limitation at O/P of first stage current source magnitude OK for 10 nsec exponential edge Scope averaging -> 16 bit resolution. Multiple waveforms captured with different DC offsets to remove scope INL effects. I/P O/P first stage amplifier

9th July, 2003CMS Ecal MGPA test results7 Pulse shapes – low gain channel signals up to 60 pC (feedback components for barrel application: 1.2k//33pF) steps not equally spaced (log attenuator) 2 active probes on +ve and –ve outputs (before any buffering) linear range +/ V around Vcm (1.25 V nom.) note: Vcm defined by external pot’l divider (5% resistors) so not exactly 1.25 V

9th July, 2003CMS Ecal MGPA test results8 Pulse shapes – all 3 gain ranges

9th July, 2003CMS Ecal MGPA test results9 Differential pulse shape – low gain channel differential probe on chip outputs (before buffering) 60 pC fullscale signal as before differential swing +/ V around Vcm corresponds to ~1.8 Volt linear range pedestal subtracted no “obvious” pulse shape distortion due to higher gain channels saturating

9th July, 2003CMS Ecal MGPA test results10 Differential pulse shapes – all 3 gain channels compared – gain ratios 1 : 5.6 : 11.3 (cf 1 : 6 : 12) no obvious interchannel distortion effects

9th July, 2003CMS Ecal MGPA test results11 Linearity and pulse shape matching – high gain channel fullscale signal 5.4 pC pulse shape matching in spec., linearity outside by factor ~2

9th July, 2003CMS Ecal MGPA test results12 Linearity and pulse shape matching – mid gain channel smallest signals show slower risetime – needs further investigation fullscale signal 10.8 pC

9th July, 2003CMS Ecal MGPA test results13 Linearity and pulse shape matching – low gain channel similar (but worse) effect as for mid-gain channel fullscale signal 61 pC

9th July, 2003CMS Ecal MGPA test results14 Pulse shape matching between gain channels Pulse shape matching definition: Pulse Shape Matching Factor PSMF=V(pk-25ns)/V(pk) Pulse shape matching = [(PSMF-Ave.PSMF)/Ave.PSMF] X 100 Ave.PSMF = average for all signal sizes and gain ranges systematic discrepancies between channels can be due to mismatch in diff. O/P termination components or (more likely here) difference in stray capacitance from PCB layout spec.

9th July, 2003CMS Ecal MGPA test results15 1 st stage of buffering differential O/P termination components (1% tolerance) mismatch of stray O/P capacitance likely due to signal routing on test card

9th July, 2003CMS Ecal MGPA test results16 effect of input capacitance on pulse shape pulse peak shifts by only ~ 3 nsec. => robust to variations in stray capacitance

9th July, 2003CMS Ecal MGPA test results17 Barrel (33 pF // 1.2k)Endcap (8.2 pF // 4k7) Cstray (~20 pF) Cstray pF simulation 200 pF Cstray (~20 pF) Cstray + 56 pF simulation 50 pF high7,0007,8506,2002,9003,0502,700 mid8,2509,1008,2003,3003,4503,073 low~ 28,000 35,400~ 8,500 9,800 Noise measurements use wide bandwidth true rms meter (single ended I/P) => need diff. to singled ended buffer circuitry => extra noise contribution to subtract will also add extra noise filtering weak dependence on input capacitance as expected estimated errors: ~ 10% high and mid-gain ranges, ~ 20% low gain range (buffer circuitry dominates here) endcap results NEW

9th July, 2003CMS Ecal MGPA test results18 10 keV X-rays (spectrum peak), dosimetry accurate to ~ 10%, doserate ~ 1 Mrad/hour, no anneal as yet ~ ½ fullscale signal injected for each gain channel ~ 3% reduction in gain after 5 Mrads lowmidhigh pre-rad 5 Mrads Radiation results: pulse shape

9th July, 2003CMS Ecal MGPA test results19 Radiation results: noise Cstray pF Cstray + 180pF +5 Mrads simulation (200 pF) high7,8507,2506,200 mid9,1008,7008,200 low~28,000~32,00035,400 no significant change (within errors) after irradiation

9th July, 2003CMS Ecal MGPA test results20 Radiation results: linearity & pulse shape matching high gain channel shown here linearity degraded slightly at extreme edge of range

9th July, 2003CMS Ecal MGPA test results21 I2C offset setting 0 I2C offset setting 105 linear range I2C pedestal offset adjustment high gain channel shown here (other channels similar) offset setting 0 -> 105 in steps of 5 (decimal) ~ optimum baseline setting here corresponds to I2C setting ~70

9th July, 2003CMS Ecal MGPA test results22 Calibration circuit functionality (1) 10pF 1nF 8 – bit DAC value 0 – 2.5 V MGPA I/P 10k Rtc on-chip external derived from external pulse high midlow distortion on rising edge for low gain channel – somehow related to external 1 nF cap.

9th July, 2003CMS Ecal MGPA test results23 Calibration circuit functionality (2) 10pF 1nF 8 – bit DAC value 0 – 2.5 V MGPA I/P 10k Rtc on-chip external with 1 nFwithout 1 nF calibration pulse shapes with/without external 1 nF show improvement if removed effect needs further investigation

9th July, 2003CMS Ecal MGPA test results24 main concern so far: high frequency instability (~ 250 MHz) can be introduced on first stage O/P when probing not clear whether problem on chip (no hint during simulation) or could be test board related decoupling components around first stage not as close in as would like VDDP, VS in particular test board for packaged chips should help with diagnosis decoupling closer in (may be cure?) bias currents easy to vary (should give clues) new version of this board also in pipeline will also take test socket

9th July, 2003CMS Ecal MGPA test results25 Power consumption Current measured in 2.5 V rail supplying test board -> ~ 245 mA -> chip current + Vcm divider (4mA) + power LED (3mA)  chip current = 238 mA measuring bias currents and multiplying by mirroring ratios -> 235 mA may change if further testing indicates changing bias conditions -> performance improvements worth having

9th July, 2003CMS Ecal MGPA test results26 Summary all results so far for one unpackaged chip, barrel feedback components to first stage gains close to specification (1 : 5.6 : 11.3) pulse shapes good linearity ~ +/- 0.2% (~ 2 x spec.) pulse shape matching within spec. apart from lowest end of mid and low gain ranges no obvious distortion introduced on lower gain channels by higher gain channels saturating => good chip layout noise close to simulation values (< 10,000 (3,500) e for mid and high gain ranges for barrel (endcap)) I2C features (channel offsets, calibration) fully functioning 5 Mrad radiation results – small effects only for more detailed studies need packaged chips

9th July, 2003CMS Ecal MGPA test results27 external components define CR and CSA gain external components define RC V/I gain resistors offset & CAL pulse generation I2C interface offset adjust MGPA – architecture overview diff. O/P

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