# Presentation: 801059

## Status of SVX4

- Kazu Hanagaki / Fermilab

-  For technical detail                                                                                         http://www-cdf.lbl.gov/users/mweber/svx4
-  Our test result                                                http://d0server1.fnal.gov/projects/run2b/Silicon/www/smt2b/readout/svx4/svx4.html

- SVX’
- 1990

- SVX2
- 1996

- SVX3
- 1998

- SVX4
- 2002

## Introduction

- Functionality is the same as SVX2/3.                                 one can choose D0 or CDF mode.
- Rad-hard by 0.25m technology by TSMC.                      up to 15Mrad.
- Real time pedestal subtraction (RTPS) capability.                                                      reducing common mode noise.

-  D0 mode: blocking FE clock in digitize/readout  Less worry for the back end activity while sampling data.
-  CDF mode: while digitize/readout, sampling data is possible.  Deadtime-less operation.

- ADC

- 8

- Charge sensitive amplifier with adjustable risetime

- Dual-ported analog pipeline

- Wilkinson type ADC 128 channels in parallel

- Zero-suppressed readout on 8-bit parallel bus

## Where we are?

- April 2002: Design submitted for fabrication
- June 10, 2002: Wafers delivered to FNAL
- June 12, 2002: First chip tested at LBNL, basic functionality verified.
- Most items meet the specification.
- Some problems.

-  D0 operation (i.e. needs FE clock for pipeline cell sampling).
-  Pedestal non-uniformity across the channels;      1) bow or slope, 2) channel to channel variation
-  Pedestal non-uniformity across the pipeline cells.

- Many tests done by lots of people    (レン, ペトロス, アンドレイ, マービン, マイク, サラ, グスタボ...)

## Outline of the rest of talk

- Brief review of tests results.                                                   not cover all the tests. I just pick up some.
- Major problems.
- Proposals for the next submission.
- Conclusions.

-  Description
-  How to fix

## Rise time measurement

- Timing scan of charge injection  looking at ADC.
- Purely front end measurement using preamp output buffer.

- FE clock

| BW | 10pF | 10pF | 33pF |
| --- | --- | --- | --- |
| 0 | 19.0 | 20 | 37.9 |
| 1 | 22.8 |  | 45.3 |
| 2 | 27.2 |  | 53.1 |
| 3 |  | 32 |  |
| 4 | 35.1 |  | 65.4 |
| 7 |  | 46 |  |
| 8 | 48.3 |  | 81.5 |

- Rise time (ns)

- Design: 25ns+(BWx4ns) for 10pF

## Gain measurement

| BW | 10pF | 33pF | 40pF |
| --- | --- | --- | --- |
| 0 | 679 | 645 | 704 |
| 6 | 714 |  | 849 |
| 15 | 678 | 795 | 1043 |

- #electrons / ADC count

| BW | 10pF | 33pF | 56pF | 82pF |
| --- | --- | --- | --- | --- |
| 0 | 877 | 923 | 940 | 1055 |
| 6 | 936 | 1009 | 1142 | 1450 |
| 15 | 1013 | 1217 | 1772 | 2051 |

- Ramp slope (001)

- Ramp slope (100)

- LSB

- MSB

## Noise

| BW=15 | Ours | Tom’s front end |
| --- | --- | --- |
| 10pF | 993 | 794 |
| 20pF | 1315 | 1034 |
| 30pF | 1637 | 1434 |

-  (~500 electrons) of additional setup noise? (Note this is <0.5ADC counts)

- For fixed rise time (69ns) by Tom Zimmerman:                                   ENC  300 + 41C (2025e- @40pF)                                        cf. this was 450 + 43.5C for the front end test chip.
- Spec. < 2000e for 40pF @ 100ns rise time.
-       very good noise performance.
- Noise can be measured as RMS of pedestal.            (noise = RMS  gain [#electrons/ADC])

## Non-linearity measured by cal_inject

- Non-linearity  ADC(meas) – Expectation(by the fit)
- Note!! This includes not only ADC but also the front-end.

- 4fC

- +/- 0.2%

## Schematic of ADC

- RamprstB

- Ramprst

- Rampup

- Rampdown

- Rref-sel

- Compref

- Rampref

- Ramprst

**8****pF**

**8****pF**

- Gain
- adjustment

- 4A

- 4A

***Ramp generator***

- -

- +

**Signal (X128)**

- -

- +

- Vth

***Common mode noise***
***discriminator***

- Thout

***Counter***
***106 MHz***

- Cp(200fF)

- (Start)

- Aref

- 4 bits DAC

**100****fF**

- -

- +

- Comprst

- Compref
- (Vdd/2)

- Comprst

- OutB

***Analog delay***

- X128

**500****fF**

**500****fF**

**10****fF**

**Clamp**

- I/V

- To FiFo

## Real Time Pedestal Subtraction (RTPS)

- Democratic vote from all 128 channels when to start the counter.

## RTPS (cont’d)

- Threshold or pedestal

- R or 1/V

## RTPS (cont’d-2)

- Cal_inject – pedestal (ADC counts) for L0 prototype

-  common mode noise is really reduced!

| #fire | 8 | 16 | 32 | 64 | 64 | 80 |
| --- | --- | --- | --- | --- | --- | --- |
| off | 66.0 ±7.2 | 65.0 ±7.2 | 68.8 ±7.5 | 69.1 ±6.9 | 73.5 ±7.4 | 71.1 ±6.5 |
| On | 65.8 ±5.9 | 64.8 ±6.1 | 67.8 ±5.2 | 68.0 ±5.2 | 72.1 ±5.5 | 69.4 ±5.4 |
| occ. (%) | 6.3 | 12.5 | 25 | 50 | 50 | 62.5 |

## Frequency Scan for readout

- Len and Mike worked on the readout frequency scan.

|  | 40% | 50% | 60% |
| --- | --- | --- | --- |
| 100MHz |  |  |  |
| 72.4MHz |  |  |  |
| 50MHz |  |  |  |

-  confirmed by single chip operation.
-  confirmed by hybrid (4chip).

- For example,         BE clock = 50MHz

- BE clock

- Duty cycle

- Usual operation range

## Double readout

- like a pointer which chip (channel) should be read out.

- Readout may be finished before token passing through a chip  double readout happen (in sparse mode).

- token

- Readout frequency (MHz)

## Data output driver

- Measured the voltage between bus and bus-bar (differential signal with 100 termination).
- Also measured the rise time and fall time to be ~3ns.

| bit | Meas. | design |
| --- | --- | --- |
| 001 | 5.6mA | 5.6mA |
| 010 | 9.4mA | 9.2mA |
| 100 | 13.2mA | 13.4mA |

- Output driver current

## Channel disabling mask

- Functionality to disable individual channel (=preamp is kept resetting) to avoid black hole effect.
- The same bits with cal_inject mask, but another bit determines whether cal_inject or disabling.

- ch.9 disabled

- huge pulse into ch. 9 (may not be B.H.)

## Yield

- 33 chips tested on the hybrid. 30 seems OK.
- 6/8 by individual chip test at stimulus machine.
- 36/41 = 88%.

- Pipeline cell and pipeline-depth (one of init parameter)

- All channels checked, but not sure for pipeline cells.

- may be different criteria

## Pipeline Cell or Depth?

- Do not mix pipeline depth and actual pipeline cell.
- Only cal_strobe in initialize mode resets the cell back to the first one.
- Pipeline cell dependence has been checked. But did we check the pipeline depth dependence? (= test of data persistence)

- Mod(45,n)

## Irradiation tests

- SEU test by 63 MeV protons. Total fluences = 1.4E14.
- Co-60 irradiation for CDF hybrid 16-18Mrad.
- D0 hybrid irradiation at KSU by 16 MeV protons.

-  SEU cross section 2.2E-17 to 1.6E-16 cm2 @95%CL
-  No major change in pedestal, noise, or gain up to ~19Mrad

-  No change of noise.
-  Small pedestal shift and small increase (!) of gain.

-  Survived 25Mrad.
-  No significant change in noise performance.

## Major problems

- Pipeline cell sampling in digitize mode in default. FE clock is needed to latch it in conjunction with PRD1 (control signal). HOWEVER, D0 mode blocks out FE clock in digitize/readout mode.  does not work in normal procedure.
- Going back and force between acquire and digitize mode.      (acquire)  (starting ADC setup)  (Pipeline sampling)  (digitize)
- Pedestal non-uniformity across channel.
- Pedestal non-uniformity across pipeline cell.

## Pedestal

- Bucket number (pipeline cell)

- channel

## Pedestal (cont’d)

- Channel dependence (and channel to channel variation)
- Pipeline cell dependence

- Ramp-up

- Ramp-down

- ADC counts

- Pipeline cell

## Pedestal Dependence on IQUI                           (comparator bias current)

- 153 A

- 190 A

- 398 A

## Pedestal shift

- The behavior is consistent with the expectation.
- NOTE!! What relevant here is the time interval between comp_rst and when comparator fires, i.e. longer is more stable.
- A setting with higher pedestal value has longer time interval internally.  the dependence is less.

- Between comp_rst and ramp_rst

## Proposal for Fixing

- For D0 operation issue:                                                         Use readout-bar signal (= either initialize, acquire, or digitize) mode, to control ADC setup lines. This enables us to set up ADC in the end of acquire mode (and of course sampling of pipeline cell).
- For pipeline dependence of pedestal:                                   Widen front end metal lines.  It is considered as the thin line causes resistance variation to each cell, and thus the cell dependence.
- For channel dependence of pedestal:                                     Redesign or modification of comparator (and analog delay).  It is considered as too slow comparator response causes the channel dependence. (see next page)

## Two versions for next submission(finally settled...)

- Version A (minimal changes): fraction 1
- Version B (pre-production): fraction 5
- Version C (Greatest redesign by Tom Zimmerman)

-   transistor sizes in comparator bias cell to speed up the comparator (x2)
-  NMOS guard ring in ADC modules

-  Redesign comparator, keeping the architecture same as the existing one.
-  Redesign ramp, and ramp pedestal generator.
-  Widen front end metal.

-  Redesign comparator using different architecture.
-  Many more.

- will be submitted

## Common Fix List

**All Versions:**
- 1) add pulldown on D0Mode
- 2) add pullup on USESEU
- 3) pullup bit7 of chipid
- 4) pulldown bit 6&7 of cellid
- 5) hardwire PRIOUT driver strength bits all ON
- 6) change ADC control signal latching scheme from “digitize” to “not(readout)”
- 7) add 2 bits to SR in frontend
- 8) add VCAL switch, VCAL resistor to AVDD only
- 9) change “feclockgating” comprst/rstb driver to 2 parallel paths, with the same strength (E_Inv1*2) as present

## Schedule

- Design work has to be finished in a week or two.
- Verification by simulation for a month.
- Next submission will be January 2003.
- Turn around will be two month???                                        next version in hand in March or April 2003 (?).

## Conclusions

- Check list going through most of the specification.        The most are within the specification.
- Yield: 36/41 (=88%)  Very preliminary.
- Three major problems, and other several minor problems.  next submission will address all these issues.
- We are about to next submission (=next January?).

- Low noise: ENC=300+41C(pF) at 69ns rise time
- Rad-hard: no problems up to 15Mrad or more.
- Real time pedestal subtraction capability

## Slide 30

## Slide 31

## Slide 32

## Comparator issue

- Signal in the output buffer seems to need some time to be stable.

- Internal delay depends on the time interval between comp_rst and when the comparator fires.
- Pedestal should depend on this time interval.
- Expect pedestal increase for larger interval.

## Observation 

## Size of bow

- The bow disappears after the long time interval. (= after the comparator reaches the saturation point, or stabilization.)