CMS FED Testing Update 28-06-2002 M. Noy J. Leaver Imperial College Silicon Group.

CMS FED TestingUpdate 28-06-2002

M. Noy & J. LeaverImperial College

Silicon Group

CMS FED Testing

Currently:

SEQSI LVDS LVTTLDAC

Evaluation board

UTP

UTP

Opto-Tx

Optical FibreOpto-

Rx

I2C master

I2C control

Coax8 bit oscilloscope

GPIB

VME

PC

LVDSLVTTLLine driver +

(optional) level shift

Network

I2C slave

CMS FED Testing Picture of the DAC evaluation board

DAC

Line driver

UTP out

LVTTL data in, from level

converter

CMS FED Testing Picture of the key link components

Opto-Tx Opto-Rx

I2Ccable

Single ended output

to scope

UTP from DAC/line

driver

Optical fibre

CMS FED Testing

DAC

scope

UTPUTP

Vout

Opto-TxDAC Evaluation Board Line driver

Opto-Rx

101110110101

CMS FED TestingSignal before the link

200mV (V+-V- =400mV ) differential signal with no offset.higher bandwidth ringing and faster rise/fall time.Time scale is relative to the scope trigger point on all plots.

CMS FED TestingSignal after the link

Single ended, with offset.No ringing but slower rise/fall times

CMS FED Testing

Signal noise/jitter after the link

Note:no scale on the width of the line. This is an impression of the infinite persistence scope trace => spread unknown. (Measurements are real).

CMS FED TestingRise time, 10% to 90% of full scale.

CMS FED TestingFall time 90% to 10% of full scale

CMS FED TestingLinearity: link is being operated in the linear region of the Tx/Rx

Settings: x0, x1, x2, x3, x4, x5=0,0,0,0,1 (recommended by CERN)

000 01

CMS FED TestingSample APV25 pair of multiplexed frames with simulated 1 MIP signal

CMS FED TestingMultiplexed APV25 header with zero pipeline address

6 start bitspipeline

address (16 bits)2 error

bits2x12x25ns bits =

CMS FED TestingZoom in of the 1 MIP signal upon its pedestal

Approx:

Pedestal value here is 509 lsbs, 4096 levels in 405mV0.099mV/lsb

1 MIP 4096/8=512 lsbs

Total signal=570+(405/4096)*(509+512)=570+0.099*1021=671mV

We attached a heating element and a thermocouple to the laser package and used the following PID equation to stabilise the temperature through a feedback loop.

W = P [ (Ts - T0) + D d (Ts- T0) /dt + I (Ts - T0)dt]

The temperature was varied between 30ºC and 40ºC in ~1ºC steps. The output of the Rx was recorded after a stabilisation time, for some measurement time.

CMS FED TestingTemperature Control

Laser threshold bias current behaves like

Ith=I0exp(T/T0)Which implies

IthIth T/T0

And (after a few lines and other things!)

Vout -Reff G Rx l Ith T/T0

Typical parameter values yield an expected (@ 34.1°C)

Vout/T -90.8 mV/°C

CMS FED TestingTemperature Measurements

CMS FED TestingTemperature Measurement Results

Approximated with a linear fit V=mT+C

Where m = -(89.8 1.8) mV/°C

and C = (4137 62) mV

Good agreement with expected value (of

90.8mV/°C), but some of the parameters are loosely

defined

Temperature stabilisation is good, with random fluctuations of the order 0.02°C. There is some unknown systematic error, that does not exceed 0.44°C.

Have statistics of 150x500 voltage points and 150 temperature points per temperature setting.

Statistical errors are too small to account for the largest random deviation, probably spurious.

We could repeat the whole measurement again using smaller T steps, but probably won’t due to time constraints.

CMS FED TestingTemperature Measurement Errors

CMS FED TestingSummary

Have a complete working single fibre, possible to drive 4 with identical signals using the current Opto-Tx.

Possible to obtain a further 2 of the 4 channel prototypes from CERN complete 12 channels could in principle be driven with identical signals.

Dependence of laser operation on temperature is now better understood, and fine temperature control is possible. We feel confident that a system such as the one we have will allow sufficient temperature stability for the fed testing needs.

Work is in progress to produce an application specific version of the SEQSIsimpler operationlonger RAM pipelineclean/synchronous stop from VMEpossible stepping through

Future Work

Have 1 (untested) Opto-Rx emulator to drive the analogue stage of the FED directly over copper (I.e. eliminating the optical link)

Verify DAC Linearity: Summer student(?)

More thought into a test vectors and their comparison with the FED output

CMS FED Testing