PI0512WS Datasheet, PDF (4/8 Pages) AMI SEMICONDUCTOR – 512-Pixel 50-mm-Pitch Wide Aperture Spectroscopic Photodiode Array

Note: Quantum Efficiency (QE) can be calculated by dividing the responsivity by the area of
the sensor's element and multiplying the resulting ratio by the energy per photon in electron
volts (eV).
The dark current is typically about 1 pA at 25^oC and will vary as function of temperature. The
dark current will contribute dark-signal charges and these charges will increase as direct
function of integration time and superimpose on the image signal charges.
Self-Scanning Circuit
Figure 5 shows a simplified electrically equivalent circuit diagram of the photodiode array.
Every photodiode in the array is connected to a common output video line by a MOS switch.
Impinging photons generate charge that is collected on each imaging photodiode when the
switch is open. As the shift register sequentially closes each MOS switch, the stored charge,
which is proportional in amount to the light exposure, from each corresponding photodiode is
readout onto the video line. The output charge on the video line from each photodiode pixel is
typically sensed by an external charge-integrating amplifier. The shift register is activated with
the entry of the start pulse. This pulse propagates through each shift register stage and
activates the MOS switches sequentially. When the pulse reaches the last shift register stage,
the fourth and last dummy pixel is readout and end-of-scan (EOS) output is held high for one
clock cycle.
VDD
START
CLK
START
CLK
SHIFT REGISTER
EOS
BIAS
RESET
AVIDEO
EOS
PI0512WS
Figure 5. Simplified circuit diagram of PI0512WS photodiode array.
PI0512WS Page 4 of 8 – July 26, 2001