RL1201LGO-711 データシートの表示（PDF） - PerkinElmer Inc

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RL1201LGO-711

L-Series Linear CMOS Spectroscopy Sensor

PerkinElmer Inc 

CMOS Spectroscopy Sensors

Figure 7. Two-Phase Drive Circuit

Clock In

+5

1K

DIP Switch

DIP Switch

DIP Switch

10 7 1 2 9 6 5 4 3

74HC161

15

4

1K

PR

2D

Q5

3 CK

74HC74

Q6

CLR

1

10

PR

12 D

Q9

11

CK

74HC74

Q8

CLR

13

10 7 1 2 9 6 5 4 3

74HC161

+5

15

10 7 1 2 9 6 5 4 3

74HC161

15

74HC04

1

2

74HC02

1

3

2

74HC04

3

45

6

4

6

5

74HC02

9

8 11 10

74HC04

Start

Phase 2

Phase 1

Dark Signal and Noise

There are two components of the

dark signal from the L-series sensors.

These are due to: (1) spatial variations

in the switching transients coupled

into the video line through the clocks

and internal multiplex switches, and

(2) the integrated dark current. A por-

tion of the switching transient effect

will be spatially random and a portion

will have the periodicity of the

clocks. The latter portion can be min-

imized by matching the clock ampli-

tudes and rise and fall times and by

good circuit layout to minimize

capacitance between clocks and

video lines. The peak-to-peak fixed

pattern due to all switching transient

effects should be less than 1% of the

saturated signal. The dark signal due

to dark current is the dark current

multiplied by the integration time.

This can be arbitrarily reduced by

lowering the temperature or by reduc-

ing the integration time.

There are three identifiable sources of

readout noise: (1) reset noise, (2) shot

noise, and (3) amplifier noise. Reset

noise is associated with resetting the

diode capacitance to a fixed voltage.

Its root mean square value is given by

(kTC)1/2/q where k is Bolzmann’s

constant, T is the absolute tempera-

ture, q is the electronic charge and C

is the total capacitance of the photo-

diode, the associated video line and

the capacitance of the external cir-

cuitry. At room temperature, kTC

noise is approximately 1500 electrons

rms. It can be reduced somewhat by

cooling. The rms value of the dark

shot noise is the square root of the

number of electrons in the dark sig-

nal charge. For example, with a room

temperature dark current of 0.25 pA

and 10 ms integration time, the rms

dark current shot noise is approxi-

mately 125 electrons. Because of the

exponential temperature dependence

of dark current, shot noise can be

reduced dramatically with a moderate

amount of cooling. Amplifier noise

depends on the amplifier circuit

used. In general, the low video output

capacitance of the L-series sensors

makes it easy to achieve low amplifier

noise, and values below 2000 electrons

are possible.

Temperature Diodes

The L-series sensor arrays have two

on-chip diodes for sensing array temp-

erature. The standard method of use

is to force a fixed forward current

(normally 100 µA) through the diodes

and measure the forward diode

voltage drop. The diode test circuitry

is shown in Figure 5. The forward diode

voltage drop at 25°C is 592.8 mV. The

equation for computing junction temp-

erature from the measured diode forward

voltage (Vf) is the familiar straight-line

equation:

Tj = K * Vf + T0

where Tj is the junction temperature,

K = -0.407 (°C/mV) is the slope or

derivative of the diode junction temp-

erature versus forward voltage (°C/mV),

Vf is the diode forward voltage and

T0 = 266.26 °C is the ordinate-intercept

or offset temperature.

www.perkinelmer.com/opto

DSP-106.01C - 10/2001W Page 6

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