Linear Photodiode Array
Imagers
Output Amplifier (cont.)
condition is not satisfied. Figure 4
details the clock waveform require-
ments and overlap tolerances.
The video amplifier buffers the signal
from the integrator for output from the
imager. Care must be taken to keep the
load on this amplifier within its ability
to drive highly reactive or low imped-
ance loads. The half power bandwidth
into an external load of 10 pF is
150 MHz. It is recommended that the
output video signal be buffered with a
wide bandwidth emitter follower or
other appropriate amplifier to provide
a large Z
IN
to the output amplifier.
Keep the external amplifier close to
the output pins to minimize stray
inductive and capacitive coupling of
the output signal that can harm
signal quality.
Table 4. Operating Voltages
Signal
ø
1
,
ø
2
Function
Horizontal Clocks
Transfer Gate
Photo Gate
Antiblooming Gate
Output Gate
Reset Gate
Amplifier Voltage Supply
Amplifier Reset Drain
Amplifier Return / Light Shield
High
Low
State
High
Low
High
Low
High
Low
High
Low
Voltage
5
0
8
0
8
-4
4
-4
3
8
0
12
9.5
0
Tolerance
±5%
±10%
±5%
±5%
±5%
±10%
±5%
±5%
ø
TG
ø
PG
ø
AB
V
OG
ø
RG
V
DD
V
RD
V
RD
/LS
Table 5. Absolute Maximum Rating
Above Which Useful Life May Be Impaired
Min
Temperature
emperature
Storage
Operating
Voltage (with respect to GND)
oltage
Pins 3, 4, 17 - 19
Pins 2, 10, 20
Pins 1, 11
Pins 15, 16
-25
-25
-0.3
-0.3
-0.3
-4.3
Max
+85
+55
+18
+18
+0
+18
Units
°C
°C
V
V
V
V
Exposure Control and
Antiblooming
An exposure control feature in the
P-series imagers supports variable
charge accumulation time in the photo-
diode. When the antiblooming gate
voltage (
ø
AB
) is set to its high state,
charge is drained from the pixel
storage gate to the exposure control
drain. During normal charge collection
in the photodiode,
ø
AB
is set to its low
state. Due to the timing requirements
of the exposure control mode, charge
is always accumulated at the end of
the period just before the charge is
transferred to the readout register.
Figure 3 includes the timing require-
ments for exposure control with the
antiblooming gate. The exposure
control timing shown will act on the
charge packets that emerge as video
data on the next readout cycle.
Precautionary Note:
The CCD output pin (Pin #2) must never be shorted to either V
SS
or V
DD
while power is
applied to the device. Catastrophic device failure will result!
Imager Performance
In P-series images each element per-
forms its own function admirably
while integrating smoothly with the
other elements on the team. The pho-
todiodes efficiently transform light
to charge, the readout registers accu-
rately transport the charge to the
amplifier, and the amplifier delivers
a clean, robust signal for use in
image processing electronics. While
the actual performance of these
imagers depends strongly on the
details of the electronics and timing
the camera provides, their straight-
forward implementation require-
ments facilitate optimum designs.
www.perkinelmer.com/opto
DSP-101 01H - 7/2002W Page 5
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