PI3042A Datasheet, PDF (8/18 Pages) AMI SEMICONDUCTOR – Contact Image Sensor Chip

Preliminary PI3042A datasheet
(4) Up is the uniformity specification, measured under a uniform exposing light
exposure. Up = [Vp(max) - Vpavg] / Vpavg x 100% or [Vpavg - Vp(min)] / Vpavg}
x 100%, whichever is greater.
Where Vp(max) is the maximum pixel output voltage in the light.
Vp(min) is the minimum pixel output voltage in the light.
The pixel Vp(n) is one n^th pixel in Npixels in the sensor.
(5) Vd = Vp(n)/Npixels. Where Vp(n) is the pixels signal amplitude of the n^th pixel
of the sensor. Dark is where light is off, leaving the image surface unexposed.
(6) Ud = Vdmax – Vdmin.
(7) Upadj = MAX[ | (Vp(n) - Vp(n+l) | / Vp(n)) x 100%. Upadj is the nonuniformity in
percentage. It is the amplitude difference between two neighboring pixels.
(8) Ucc is the uniformity specifications, measured among the good die on the wafer.
Under uniform light exposure the sensors are measured and calculated with
following algorithm: Vpavg of all the good dies on the wafer are averaged and
assigned VGpavg. Then the die with maximum Vpavg is assigned Vpavg(max),
and the one with minimum Vpavg is assigned Vpavg(min). Then UCC =
{[Vpavg(max)-Vpavg(min)]/VGpavg}x100.
Measuring The Device’s High Frequency Performances
The PI3042A devices were tested on an A6 length standard CIS module’s PCB. Thirteen sensors
bonded on the PCB board along with its support circuits, such as, clock buffer circuits, the shunt
switch, SW, and its amplifier. The board’s video line capacitance, input capacitance of SW and input
capacitance of the amplifier become part of the CAP. The A6 PCB was selected because together
with the shunt switch, SW, and with its amplifier input, the video line had a typical value of ~100pf
including its stray from its PCB copper traces. Another reason for this selection is that the PI3042A
wafer probe tests of these devices are similarly setup using this method.
By removing RIN, the amplifier gain was set to one. Then with the total value of CAP at ~100pf the
Video Pixels Voltage amplitude gives a measure of the approximate Pixel charge. Note the amplifier is
a 1:1 buffer amplifier that serves to isolate the video line from the measuring instruments. Further note
that when the modules are produced, RIN is in the circuit as variable resistor. Then, in production of
the CIS modules, the video output amplitude, Vpavg, can be adjusted to the module’s specified level.
This factory adjust is required because the exposure is fixed (Exposure = Light Power X Time).
Example, the module’s light power is fixed and integrations time, Tint, is fixed. Note Tint is fixed in
accordance to users requirement, or specified for factory adjustment procedure during production. In
either case, the light exposure is fixed. Accordingly, to adjust the voltage amplitude to the specified
level, RIN is used.
Since the sensor response vary as a function of color, the PI3042A is measured with a Yellow-Green
LED light source, as well as, the Red (660 nm) LED light source. The light sources were selected
because historically, these LED light bars were used in the CIS industry and accepted in the low-cost
CIS markets. Today, the users are turning towards the Light Guides or Light Pipes as the costs have
been reducing and the image sensor’s technology continually improves. Yet, in low-cost applications
and, especially in mid-size volume production, the light bars and the older image sensors persistently
continues to be in demand by the scanning industry.
Page 8 of 18 Date: 09/23/05