Charge Measurement Using Commercial Devices

Jinyuan Wu, Zonghan Shi

For CKM Collaboration.

Jan. 2003

Introduction

PMT

QAD6644 FPGAIntegrator

HP1662C

AD6644

FPGAIntegrator(1)AD8055

Input Pulse

EPC2LC20

Integrator (2)OPA660

To Analyzer

The Circuit Board

All test equipments

Outline

• AD6644.

•Integrator circuit (1).

•ADC output.

•AD6644 stability

•Integrator circuit (2).

Commercial ADC: AD6644• The AD6644 is a high speed, high-

performance, monolithic 14-bit analog-to-digital converter.

•Current FPGA technology is used in our tests.

•The sample rate in our tests is 35 MHz or

the sample time is 28.5ns.

•The guaranteed sample rate is 65 MSPS.

Integrator for ADC [1]

+2.5V

GND

Input Pulse

100pf

36.5k

_

+

AD805551OUTPUT

•The output will send to AD6644 as a input signal.

•It is a traditional integrator.

•T=RC=36.5k x 100pf=3.65us=128 x 28.5ns

Input Pulse

Output

Input Pulse

Output

Digital Process of AD6644 Output

• Using FPGA hardware to find charge.

ADC ADCQ

SUB ABS

OR

AND

Higher Bits

DIFF

D

D

Simple Zero Suppression Algorithm

= Charge

DIFF = Charge

ADCQ

Data from HP 1662C Logic Analyzer

ADCQ

Charge

The Stability of AD6644

256

D

ABSEN

R(RESULT)SUB D

D(DATA FROM AD6644)

•Above circuit is used to produce the mean of absolute difference.

256

255

0)1(

nnn DD

R

• DC input is sent to AD6644.

Data From HP 1662C Logic Analyzer

Result

ADCQ

The Mean of Absolute Difference

191406.1256

)305(

256

)131(

256

255

0)1(

dechexn

nn DDR

ADCQ

ADC Output of DC Input

Standard Deviation

)146( 011904.1)(

1

2

n

n

XXn

ii

Integrator for ADC [2]

GND

Input Pulse

GND

51

150

GND

51

150

17

OUTPUT

100pf

36.5k

5V

5 6

3

8

2OPA660OperationalAmplifier & Buffer

+1

Similar as Ken Nelson’s design except the omission of the reset circuits.

Input Pulse

Output

Input Pulse

Output

Additional Works To Be Done

• Connect to the QIE test system in Lab 6.

• The test for Integrator (2).

Thanks

Input Pulse

Output

Integrator (1)

Input pulse

Output

Integrator (2)