mlx90255-bc Melexis Company, mlx90255-bc Datasheet - Page 5

• Manufacturer Part Number: mlx90255-bc
• Description: Linear Optical Array
• Manufacturer: Melexis Company

4. General Description
(continued from page 1)
This causes all 132 sampling capacitors to be
disconnected from their respective integrators
and starts an integrator reset period. As the SI
pulse is clocked through the shift register, the
charge stored on the sampling capacitors is
sequentially connected to a charge-coupled
output amplifier that generates a voltage on the
analog output AO. Two dummy pixel values are
shifted out first, then the 128 actual pixel bits,
followed by two additional dummy pixel bits, for
a total of 132 data bits. Although there are only
132 pixels, 133 clock pulses are necessary for a
complete shift out. The final pulse is used to re-
initialize the shift register.
The integrator reset period ends 18 clock cycles
after the SI pulse is clocked in. So the light-
integration starts after the 18
light-integration ends at the next SI pulse.
Between the end of the 133
next SI pulse, a minimum time of 10µs is
necessary for an effective S&H function. So the
minimum integration time of the MLX90255BC is
(133 -18) * Ts + 10µs and thus dependent on
clock speed. (Ts = clock period) After the 132
data bits are clocked out, the output becomes
high impedance. (see figure) The AO is driven
by a source follower that requires an external
pulldown resistor. (typically 330Ω) The output is
nominally 125mV for no light input and 2.4V for a
nominal full-scale output. The pixel gain is 15%
bigger at the edges than in the middle (cosine
correction) in order to get a flat output when
illuminating the device with a single LED light
source (see also Section 6).
The MLX90255BC is intended for use in a wide
variety
scanning, mark and code reading, optical
character
imaging, edge detection and positioning, and
390109025503
Rev. 001
of
recognition
applications,
(OCR)
th
clock pulse and the
including:
th
CLK pulse. The
and
contact
image
Page 5 of 12
optical
MLX90255BC is a replacement for the Texas
Instruments' TSL1301 and TSL1401 parts.
5. Absolute Maximum Ratings
Stresses beyond those listed under "absolute
maximum
damage to the device.
These are stress ratings only, and functional
operation of the device at these or any other
conditions
"recommended operating conditions" is not
implied.
Exposure
conditions for extended periods may affect
device reliability.
linear
MLX90255-BC
ratings"
beyond
to
and
Linear Optical Array
absolute-maximum
may
those
rotary
cause
indicated
encoding.
permanent
Nov/05
-rated
under
The