Status of 8ch calib prototype N. Dumont-Dayot, G. Perrot, P. Perrodo, I Wingerter-Seez LAPP Annecy U. Schafer, D. Schroff, Univ Mainz C. de La Taille, N. Seguin-Moreau, L. Serin LAL Orsay ATLAS

21 jun 2002C. de La Taille calibration board design review 2 8ch prototype status Slice of 8 analog channels + complete digital part 3 boards received in apr 02 2 in Orsay (-> 1 to Mainz), 1 in Annecy Opamps & switch DAC Calolgic TTCRx Delay SPAC2 8 outputs

21 jun 2002C. de La Taille calibration board design review 3 8channel prototype chips DAC V2 Improved reference 123 chips received may work OK QFP100 Opamp V2 offset trimmed to 15 µV HF switch integrated 463 chips available QFP44 Calogic V2 40 chips available in QFP100 Tested to SEE in Louvain

21 jun 2002C. de La Taille calibration board design review 4 Digital part Worked OK at once TTCRx + Calogic + Delay chip + SPAC3 Jitter visibly improved

21 jun 2002C. de La Taille calibration board design review 5 DC uniformity Correction of output line resistance t = 35 µm R = 0.5 mΩ/ ΔL = 17 cm W = 200 µm Expect : ΔR line = 0.4 Ω ΔV out = 0.8 % effect Correction by ΔR (5Ω) decreasing Iout by increasing R(5Ω) Exact correction for W = 2mm : ΔR5 =40 mΩ Measured value = 60 mΩ -> overcompensation Rout ( Ω) 10*ΔR (5Ω) CH0CH7 VP6 layer output layer

21 jun 2002C. de La Taille calibration board design review 6 DC uniformity DC current output 1.4% variation between CH0 and CH7 Consistent with +5.5V additionnal resistance 5 Ω resistors All in ± 0.1% Rms = 0.04% 2 resistors where low by 1% : DAMAGED ?

21 jun 2002C. de La Taille calibration board design review 7 Lots of unexpected problems… Board very different from mod0 Channels no longer aligned but staggered in depth Lots of problems with the 8 channels Ground bounce 2V change with enabled channels 80 µV DAC offset DAC change with all channels on Overshoot Signal uniformity DC uniformity Damaged chips Oscillations Ripple noise Linearity

21 jun 2002C. de La Taille calibration board design review 8 Example : Ground bounce Observation 100 ns bounce on small signals Worst on far channels (->7) Clean on channel 0 Present even with collector open Dissapears if termination resistor (R0) removed Explanation Large digital current (200 mA) in inductive ground Produces 1 mV ground bounce, coupled to the output through R0 Cure Try to reduce digital current (difficult) Move R0 in quiet zone near inductor Minimize loop area around NE856

21 jun 2002C. de La Taille calibration board design review 9 Parasitic injected charge (PIC) L = 0, 22 nH, 100 nH Parasitic signal when DAC=0 Proportionnal to C GS and ΔV GS ringing with parasitic inductance (L ~ 3 nH) Reducing V G can reduce the PIC Effect very visible, scaling with VGS Below V G = - 0.4V, some PMOS are not completely OFF : not acceptable Improved by connecting the nwell to the source Referred to DAC value Peak of PIC after shaping 1 V DAC makes 5 V output pulse 1 GeV (η=0,MID) corresponds to DAC=500 µV

21 jun 2002C. de La Taille calibration board design review 10 Parasitic injected charge (PIC) Parasitic injected charge extraction DAC set at \x0004 = 64 µV Signal due to offset needs to be substracted

21 jun 2002C. de La Taille calibration board design review 11 Parasitic injected charge (PIC) Parasitic injected charge very uniform on 8 channels Equivalent to DAC=0006=100 µV (180 MeV in the barrel middle) in peak Subsequently reduced by a factor ~3, very close to noise level (50MeV) Well differentiated Injected charge x 10 = 500 µV pulse ~DAC=100µV

21 jun 2002C. de La Taille calibration board design review 12 Linearity Measured on each gain Pulse measurements In red After shaping DC current measur. In black With Keithley Several problems DAC referenced to VP6 Bad 5Ω resistor brand Well below 0.1%

21 jun 2002C. de La Taille calibration board design review 13 Linearity Fit residuals show opamp offset Very small contribution of parasitic injected charge Offset of High gain range in agreement with low offset Opamp measurement Effect too small to be seen in other ranges

21 jun 2002C. de La Taille calibration board design review 14 Slope different by 5 % in high gain range due to attenuator accuracy  = 0.3 % but 5 V stripline compensation deteriorates the uniformity Linearity Fit slopes give uniformity Very small contribution of parasitic injected charge

21 jun 2002C. de La Taille calibration board design review 15 slope uniformity 0.3 % 1.5 % effect from 5.5 V compensation foreseen when 50  near switch 0.6 % from different output lenghes from 50  to connector (on 128 boards connector position will add a few per mille 5  resistor at 0.1 % as expected What should we compensate on 128 boards ? Pulse uniformity

21 jun 2002C. de La Taille calibration board design review 16 Oscillations Observation 1 Large oscillation at 350 MHz when channels 2,3 or 4 are pulsed together with DAC>0.25V Barely visible oscillation at 350 MHz on all the channels, increasing with DAC>0.25V Was not present on single channel test-board Explanation 1 None (as usual for HF oscillations) Cure 1 Add 150 pF to ground on Cp (gate of current source output transistor) Observation MHz oscillation on large pulses, alters decay time Explanation 2 Delay chip loaded by coax for triggering purposes Cure 2 Add 50 Ω in series for trigger output

21 jun 2002C. de La Taille calibration board design review 17 Damaged opamps Observation + 2V moves up to 5.5 V Some chips (4/18) show large current (5-50mA) from 7.5V to +2V They still work correctly, but with degraded offset All chips in parallel on supplies, common 100 Ω protection resistor on +2 V Difficult to locate bad chips Explanation None, could only be reproduced with 7.5V raised to 15V Several power supplies mishandlings have been tried without damage Cure Individual current limitation resistors on +2V and +7.5V Series resistors on input and common voltage busses (Vref)

21 jun 2002C. de La Taille calibration board design review 18 Damaged DAC Observation 1 chip damaged on brd 3 DAC = 0 gives 2 mV 4 µA leakage current on MSB Explanation None Chip could not be remounted on DAC test board (pins damaged) Cure To be examined

21 jun 2002C. de La Taille calibration board design review 19 Enable schematic Common emitter between V DD and V SS Channels enabled flow 1 mA in V SS Channels ON by default (Enable=V DD ) Go to common base configuration Powered between V DD and GND No current in V SS Base connected to V CC through 47 kΩ Channels OFF by default 50K VCC 100K VDD Enable 2-7V Calogic 0-5V VSS 100K VDD Enable 2-7V 5K Calogic 0-5V

21 jun 2002C. de La Taille calibration board design review 20 Robustness Power supplies Effect of missing +7.5V : maximum current flowing (0.3A/ch) -> add 1MΩ to 5.5V on output transistor Effect of missing +9.5V : maximum current flowing (0.3A/ch) -> Produce +7.5V from +9.5V Effect of missing +5.5V : none. Effect of missing -6 V : barely visible, can be almost any (negative) value Tests of robustness The chip starts to deteriorate at V DD = 12 V Permanent damage in protection diodes, if unlimited current for V DD = 14 V Offset variations Observation : offset changes by 40 µV when all channels are ON Explanation : Offset sensitivity to Vss power supply : dV off /dV 2V = 100 µV/V = 0.01% Cure : Reduce +2V impedance by decreasing resistance in series with the 3 diodes Maintain robustness by individual large resistive decoupling Use regulator on +7.5V

21 jun 2002C. de La Taille calibration board design review 21 Summary of proposed modifications General Power supplies reduced by 0.5V to VP6=+5V, V DD =+7V and VP9=+9V Individual channels R0 = 50 Ω moved away from switch, close to inductor Output line impedance decreased to 25 Ω Bulk connected to source instead of VDD via 1 MΩ, 100 nF decoupling Gate connected to GND, no VG adjustment 150 pF to ground on Cp and 1 MΩ to V DD 1 kΩ in series with Vss = + 2 V (I = 100 µA) 200 Ω in series with fuses to Vss (I = 2 mA) 100 Ω in series with Vdd = +7V (I = 2.1 mA) Enable translator changed from common emitter to common base configuration, with no connection to Vss Short path between emitter of switching NE856 and decoupling capacitor of preceding emitter follower. Series resistor of follower increased from 51 Ω to 82 Ω (910 Ω was really too much !)

21 jun 2002C. de La Taille calibration board design review 22 Summary of proposed modifications Groups of 8 channels Remove 50 Ω parallel termination on command line Change 0 Ω series termination to 50 Ω // 33 pF Add fuse on VP6 if R FUSE < 50 mΩ Have local +2V with 3 diodes Keep possibility of local VG = -0.4 V ? DAC Correct star disribution for VP6 on resistor ladder Keep bandgap and reference possibility DAC distribution 150 pF to ground on Cp and 1 MΩ to Vdd Connect drain to ground via 1 k instead of using PMOS switch 1 kΩ in series with Vss = + 2 V (I = 100 µA) 200 Ω in series with fuses to Vss (I = 2 mA) 100 Ω in series with Vdd = +7V (I = 2.1 mA)

21 jun 2002C. de La Taille calibration board design review 23 Pending questions Digital part Clock terminations Reset scheme Regulator on +5V Maximum current : 3A => All channels ON with DAC=100mV (1/10 full scale) 10 channels with maximum DAC Filtering Use of Bandgap reference Not yet tested Schedule for opamps production Issue order in june ? How many wafers : 12, 13, 14 ?

21 jun 2002C. de La Taille calibration board design review 24 Pulse shape before shaping DAC=1V -40dB DAC=0.1V -20dB DAC=10mV 0dB DAC=1mV 0dB DAC=100µV Full DAC range 100 µV-> 1V Up to 5V pulses in 50 Ω Undershoot Due to 50 Ω line between switch and R0 : should be 25 Ω Checked by simulation Will be corrected Risetime < 2 ns Varies little with DAC

21 jun 2002C. de La Taille calibration board design review 25 Pulse shape after shaping DAC=1V -80dB DAC=1mV -20dB DAC=100µV 0dB DAC=0µV 80 dB dynamic range Parasitic injected charge Equivalent to DAC=30 µV Or a pulse of 150 µV At peak < 15 µV Improvement by >10 compared to module0

21 jun 2002C. de La Taille calibration board design review 26 PIC uniformity PIC on 8 channels Good uniformity Singularities : CH7 had the Nwell tied to 5V, as in the original configuration : clear improvement ! CH4 has a larger offset (35 µV) damaged ? DAC=1mV -20dB CH7 : VB=+5V

21 jun 2002C. de La Taille calibration board design review 27 Designing the 128ch board Large number of modifications ! 108 modification on the 8 ch. Board alone Improved performance and robustness Power supplies decreased by 0.5V Goal : have VP6 = 5V uniform for all channels within 0.1% Star configuration mandatory All VP6 lines equalized in length Common reference point on borad center : dimension 2 x 1 cm = 1 mΩ Minimize variation of amplitude with number of enabled channels Many tricky PCB layout details 150 mm 220 mm 5V ref

21 jun 2002C. de La Taille calibration board design review 28 Schematics : power supplies Regulators on VP9 and VP7 from +11V. Also on VP5 ? Regulators on digital Vcc for delays and logic chips

21 jun 2002C. de La Taille calibration board design review 29 Schematics : TTCRx Derives 40 MHz clock and calib pulse (CMD) No EPROM used

21 jun 2002C. de La Taille calibration board design review 30 Schematics : SPAC

21 jun 2002C. de La Taille calibration board design review 31 Schematics : calogic 1 chip for counter, 1 for DAC and 4 for Enables

21 jun 2002C. de La Taille calibration board design review 32 Schematics : delay chips Delay chip : AC output as it can be stuck to Vcc Trigger output on front panel

21 jun 2002C. de La Taille calibration board design review 33 Schematics CMD distribution : White follower

21 jun 2002C. de La Taille calibration board design review 34 Schematics : DAC Careful separate layout of VP5 and GND External reference to VP9 Internal low offset opamp connected as others

21 jun 2002C. de La Taille calibration board design review 35 Schematics : DAC distribution Low offset opamp for low impedance DAC fanout to 128 channels External fuses ?

21 jun 2002C. de La Taille calibration board design review 36 Schematics : 1 pulser Low offset opamp for current source HF switch with external NE856 New enable schematic

21 jun 2002C. de La Taille calibration board design review 37 PCB layout Top layer : analog components Bottom layer : digital components

21 jun 2002C. de La Taille calibration board design review 38 PCB layout Layer 2Layer 3

21 jun 2002C. de La Taille calibration board design review 39 PCB layout Layer 4Layer 5

21 jun 2002C. de La Taille calibration board design review 40 PCB layout Layer 6Layer 7

21 jun 2002C. de La Taille calibration board design review 41 PCB layout PCB cross section : all inner copper layers 70 µm thickness Layer 1 Layer 2 Output connectorAnalog partDigital part GNDrouting Layer 3 Layer 4 outputs GND Layer 5 Layer 6 outputs GND Layer 7 Layer 8 GND Inductors GND outputs GND outputs GND enables VP5 GND VP5 routing GND enables VP5 routing GND VP5 outputs

21 jun 2002C. de La Taille calibration board design review 42 Summary The operation of the 8 channels board has been more difficult than foreseen Layout very different from module 0 Coupling of large digital signals Many modifications necessary Robustness had been overlooked Performance is good Linearity < 0.1% Parasitic injected charge ten times better than on module 0 The 128 channel is being finalized Difficult layout of uniform VP6 : star configuration Many lines equalized in length Pending issues Voltage regulator on VP5 (pin 4)