NOIS1SM0250A-HHC ON Semiconductor, NOIS1SM0250A-HHC Datasheet - Page 10

• Manufacturer Part Number: NOIS1SM0250A-HHC
• Manufacturer: ON Semiconductor

Specifications of NOIS1SM0250A-HHC

• Lead Free Status / Rohs Status: Supplier Unconfirmed

Shift Registers
The shift registers are located next to the pixel array and contain
equal number of outputs and pixel array rows. They are designed
as "1-hot" registers, (YL and YR shift register) each allowing
selection of one row of pixels at a time. A clock pulse moves the
pointer one position down the register resulting in the selection
of every individual row for either reset or readout. The spatial
offset between the two selected rows determines the integration
time. A synchronization pulse to the shift registers loads the
value from a preset register into the shift register forcing the
pointer to a predetermined position. Windowing in the vertical (Y)
direction is achieved by presetting the registers to a row that is
not the first row and by clocking out only the required number of
rows.
Column Amplifiers
All outputs from the pixels in a column are connected in parallel
to a column amplifier. This amplifier samples the output voltage
and the reset level of the pixel whose row is selected at that
moment and presents these voltage levels to the output
amplifier. As a result, the pixels are always reset immediately
after readout as part of the sample procedure and the maximum
integration time of a pixel is the time between two read cycles.
Electronic Shutter
In a linescan integrating imager with electronic shutter, there are
two continuous processes of image gathering.
Line number
Rev. 7 | www.onsemi.com | Page 10 of 22
Figure 9. Electronic Shutter
Frame time
y
Reset sequence
The first process resets lines in a progressive scan. At line reset,
all the pixels in a line are drained from any photo charges
collected since their last reset or readout. After reset, a new
exposure cycle starts for that particular line.
The second process is the actual readout, which also happens
in an equally fast linewise progressive scan.
During readout, the photo charges collected since the previous
reset are converted into an output voltage. This is then passed
on pixel by pixel to the imager's pixel serial output and ADC.
Readout is destructive, meaning the accumulation of charges
from successive exposure phases is not possible in the present
architecture.
The STAR250 has two Y shift registers; YL and YR. One is used
to read out a line (YL) and the other is used to reset a line (YR).
The integration time is equal to the time between the last reset
and readout of that line, see
calculated as follows:
Integration time = (Nr. Lines × (RBT + pixel period × Nr. Pixels))
with:
■
■
■
■
Nr. Lines: Number of lines between readout and reset (Y).
Nr. Pixels: Number of pixels read out each line (X).
RBT: Row Blanking Time = 3.2 s (typical).
Pixel period: 1/8 MHz = 125 ns (typical).
y
x
Integration time
Time axis
Reset line
Read line
x
Figure
NOIS1SM0250A
9. The integration time is