REVISION NUMBER: REV A
DATE: 09/26/05
PAGES: Page 1 of 18
PI3042A
Contact Image Sensor Chip
Preliminary Data Sheet
Preliminary PI3042A datasheet
PI3042A
400DPI CIS Sensor Chip
Engineering Data Sheet
Description:
Peripheral Imaging Corporation PI3042A CIS, Contact Image Sensor is a 400 dot per inch
(dpi) resolution, linear array image sensor chip. The sensor chip is processed using PIC’s
proprietary CMOS Image Sensor Technology. Designed for cascading multiple chips in a
series, the image sensor chips, using chip-on-board process, are bonded end-to-end on a
printed circuit board (PCB). This bonding process allows users to produce variable CIS
module lengths in increments of chip array lengths. Hence, the wide variety of image reading
widths can easily be applied to the numerous document scanners, found in facsimile, as well
as, the narrow width scanners, such as, those found in check readers, lotto tickets, entrance
gate tickets and other office automation equipment which requires a wide variety of scanning
widths.
Figure 1 is a block diagram of the imaging sensor chip. Each sensor chip consists of 128 detector
elements, their associated multiplexing switches, buffers, and a chip selector. The detectors
element-to-element spacing is approximately 62.5 µm. The size of each chip without scribe lines is
8080 µm by 385 µm. Each sensor chip has 7 bonding pads. The pad symbols and functions are
described in Table 1.
8080µm
1
2
3
4
Row of 128 Sensors
125
and Video Signal
Multiplexers
Readout Shift Register
126
127
128
385µm
Buffer
SP
Buffer
CP
VDD DGND
Chip
Select
IOUT
Buffer
AGND EOS
Figure 1. PI3042A Block Diagram
SP
CP
VDD
DGND
IOUT
AGND
EOS
SYMBOL
FUNCTION
Start Pulse: Input clock to start the line scan.
Clock Pulse: Input clock to clock of the Shift Register.
Positive Supply: +5 volt supply connected to substrate.
Digital Ground: Connection topside common
Signal Current Output: Output for video signal current
Analog Ground: Connection topside common
End of Scan Pulse: Output from the shift register at end of scan.
Table 1. Pad Symbols and Functions
Page 2 of 18 Date: 09/23/05
Preliminary PI3042A datasheet
Bonding Pad Outputs Locations and Die Dimensions
Figure 2 shows image sensor’s die dimension and the bonding pad locations for PI3042A Sensor Chip. The location is
referenced to the lower left corner of the die.
Figure 2. Bonding Pad and Chip Layout
Page 3 of 18 Date: 09/23/05
Preliminary PI3042A datasheet
Wafer Scribe Lines Bordering The Die
Figure 3 shows the wafer scribe lines bordering the PI3042A Sensor Chip. The wafer thickness is 350 µm.
70 µm
Scribe width
380 µm
SENSOR DIE
DIMENSION
PIXEL PITCH = 62.5 µm
WAFER THICKNESS = 350 µm
60 µm
880 µm
60 µm
70 µm
Figure 3. Wafer Scribe Lines
Page 4 of 18 Date: 09/23/05
Prelininary PI3042A datasheet
Output Circuit Of The Image Sensor
The video signal from each photo-site is connected to a common video line on the sensor.
Each photo-site is composed of a phototransistor with a series MOS switch connecting its
emitter to a common video line. The video line is connected to the pad labeled IOUT. The
photo-sites are readout upon the closure of the MOS switch, which is sequentially switched on
and off by its internal scanning shift register,
see
Figure 1, PI3042A Block Diagra
m
. For the
clock & timing operation of the image sensor see Figure 7, Timing Diagram Of The PI3042A
Sensor. The photo-sensing element is the base of the phototransistor where it detects and
converts the light energy to proportional charges and stores them in its base and collector
capacitance. When the MOS switch is activated, the emitter is connected to the video line and
acts as source follower, producing an impulse current proportional to the stored charges in the
base. This current is a discrete-time analog signal output called the video pixel. The charges in
the video pixel are proportional to the light energy impinging in the neighborhood of its photo-
sites. Figure 4, Video Pixel Output Structures, show a output structure of four photo-sites out of
128. The multiplexing MOS switch in each photo-site terminates into the output pad, IOUT,
through a common video line. As the shift register sequentially accesses each photo-site the
charges of the video pixel is sent to the IOUT where they are processed with an external signal
conversion circuit. See the follow section, Signal Conversion Circuit.
Figure 4. Video Pixel Output Structures
Signal Conversion Circuit
Figure 5, Video Output Test and Application Circuit is an example of the charge conversion that
is used in the CIS modules. It is usually bonded on the same PCB on which the image sensors
are bonded. In applications where cost is an important factor, this simple circuit provides the
cleanest technique in processing the video output. It integrates all the currents from each pixel
element onto a capacitor, CAP. It, also, sums the switch edge’s energy along with the signal
current pulses, hence minimizes the switching patterns on the video pixels. The summed
charges stored on the CAP, produce a pixel voltage. Its voltage amplitude is proportional to the
charge from the current pulse and the value of the CAP.
Page 5 of 18 Date: 09/23/05
