NMOS linear image sensor
Figure 9 Readout circuit example and timing chart
+5 V
S3901/S3904 series
50 ns MIN.
10 kΩ
st
1
2
st
1
2
Vscg
Vss
Vsub
NC
ACTIVE
VIDEO
Vscd
+
–
EOS
DUMMY
VIDEO
OPEN
EOS
st
RESET
1, Reset
2
10 pF
KMPDC0024EA
+
OP-AMP (JFET INPUT)
+2 V
KMPDC0023EA
Output voltage Vout is
Output charge [C]
Vout [V] =
10 × 10
-12
[F]
shown in.
s
Anti-blooming function
If the incident light intensity is higher than the saturation charge level, even partially, a signal charge in excess of the saturation
charge cannot accumulate in the photodiode. This excessive charge flows out into the video line degrading the signal purity. To
avoid this problem and maintain the signal purity, applying the same voltage as the video bias voltage to the saturation control
drain and grounding the saturation control gate are effective. If the incident light intensity is extremely high, a positive bias should
be applied to the saturation control gate. The larger the voltage applied to the saturation control gate, the higher the function for
suppressing the excessive saturation charge will be. However, this voltage also lowers the amount of saturation charge, so an
optimum bias voltage should be selected.
s
Auxiliary functions
1) All reset
In normal operation, the accumulated charge in each photodiode is reset when the signal is read out. Besides this method that
uses the readout line, S3901/S3904 series can reset the photodiode charge by applying a pulse to the saturation control gate.
The amplitude of this pulse should be equal to the
φ1, φ2
and
φst
pulses and the pulse width should be longer than 5
µs.
When the saturation control gate is set at the “High” level, all photodiodes are reset to the saturation control drain potential
(equal to video bias). Conversely, when the saturation control gate is set at the “Low” level (0 V), the signal charge accumulates
in each photodiode without being reset.
2) Dummy video
S3901/S3904 series have a dummy video line to eliminate spike noise contained in the video output waveform. Video signal
with lower spike noise can be obtained by differential amplification applied between the active video line and dummy video
line outputs. When not needed, leave this unconnected.
s
Handling precautions
1) Electrostatic countermeasures
NMOS linear image sensors are designed to resist static electrical charges. However, take sufficient cautions and countermea-
sures to prevent damage from static charges when handling the sensors.
2) Window
If dust or grime sticks to the surface of the light input window, it appears as a black blemish or smear on the image. Before using
the image sensor, the window surface should be cleaned. Wipe off the window surface with a soft cloth, cleaning paper or
cotton swab slightly moistened with organic solvent such as alcohol, and then lightly blow away with compressed air. Do not
rub the window with dry cloth or cotton swab as this may generate static electricity.
Information furnished by HAMAMATSU is believed to be reliable. However, no responsibility is assumed for possible inaccuracies or omissions.
Specifications are subject to change without notice. No patent rights are granted to any of the circuits described herein. ©2005 Hamamatsu Photonics K.K.
HAMAMATSU PHOTONICS K.K., Solid State Division
1126-1 Ichino-cho,
Higashi-ku,
Hamamatsu City, 435-8558 Japan, Telephone: (81) 53-434-3311, Fax: (81) 53-434-5184, www.hamamatsu.com
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Germany: Hamamatsu Photonics Deutschland GmbH: Arzbergerstr. 10, D-82211 Herrsching am Ammersee, Germany, Telephone: (49) 08152-3750, Fax: (49) 08152-2658
France: Hamamatsu Photonics France S.A.R.L.:
19,
Rue du Saule Trapu, Parc du Moulin de Massy, 91882 Massy Cedex, France, Telephone: 33-(1) 69 53 71 00, Fax: 33-(1) 69 53 71 10
United Kingdom: Hamamatsu Photonics UK Limited: 2 Howard Court, 10 Tewin Road, Welwyn Garden City, Hertfordshire AL7 1BW, United Kingdom, Telephone: (44) 1707-294888, Fax: (44) 1707-325777
North Europe: Hamamatsu Photonics Norden AB: Smidesvägen 12, SE-171 41 Solna, Sweden, Telephone: (46) 8-509-031-00, Fax: (46) 8-509-031-01
Italy: Hamamatsu Photonics Italia S.R.L.: Strada della Moia, 1/E, 20020 Arese, (Milano), Italy, Telephone: (39) 02-935-81-733, Fax: (39) 02-935-81-741
Cat. No. KMPD1036E01
Oct.
2005 DN
HAMAMATSU [ HAMAMATSU CORPORATION ]
