AMIS-720442-A: 400dpi Contact Image Sensor
Data Sheet
1.0 Description
AMI Semiconductor’s AMIS-720442-A (PI3042A) contact image sensor (CIS) is a 400 dots per inch (dpi) linear array image sensor
chip. The sensor chip is processed using a CMOS image sensing technology, belonging to AMIS. 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 the manufacturers to produce variable CIS module lengths in increments of chip array lengths. This allows a
wide variety of image reading widths which are easily applied to the numerous document scanners found in facsimile, as well as the
narrow width scanners, such as, those found in check reader, lotto tickets, entrance gates tickets, etc. Included in this list of scanners
are various types of automated office equipment which require 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 detector's element-to-element spacing is approximately 62.5µm. The size of
each chip without scribe lines is 8080µm by 385µm. Each sensor chip has seven bonding pads. The pad symbols and functions are
described in Table 1.
8080
m
Row of 128 Sensors
and Video Signal
Multiplexers
Readout Shift Register
385
m
Buffer
SP
Buffer
CP
VDD DGND
Chip
Select
IOUT
Buffer
AGND EOS
Figure 1: AMIS-720442-A Block Diagram
Table 1: Pad Symbols and Functions
Symbol
Function
SP
Start pulse: input clock to start the line scan
CP
Clock pulse: input clock to clock of the shift register
VDD
Positive supply: +5V supply connected to substrate
DGND
Digital ground: connection topside common
IOUT
Signal current output: output for video signal current
AGND
Analog ground: connection topside common
EOS
End-of-scan pulse: output from the shift register at end-of-scan
AMI Semiconductor
– May 06, M-20571-001
www.amis.com
1
AMIS-720442-A: 400dpi Contact Image Sensor
2.0 Bonding Pad Output Locations and Die Dimensions
Data Sheet
Figure 2 shows the die dimensions of the image sensor and the bonding pad locations for the AMIS-720442-A sensor chip. The location
is referenced to the lower left corner of the die.
Figure 2: Bonding Pad and Chip Layout
AMI Semiconductor
– May 06, M-20571-001
www.amis.com
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AMIS-720442-A: 400dpi Contact Image Sensor
3.0 Wafer Scribe Lines Bordering the Die
Figure 3 shows the wafer scribe lines bordering the AMIS-720442-A sensor chip. The wafer thickness is 350µcrons.
Data Sheet
Figure 3: Wafer Scribe Lines
AMI Semiconductor
– May 06, M-20571-001
www.amis.com
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AMIS-720442-A: 400dpi Contact Image Sensor
4.0 Output Circuit of the Image Sensor
Data Sheet
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 read out upon the closure of the MOS switch, which is sequentially switched on and off by its internal
scanning shift register. See Figure 1. For the clock and timing operation image sensor see Figure 11. 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 the 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 shows an 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 are sent to the IOUT where they are processed with an external signal conversion circuit (see Section 5.0).
Figure 4: Video Pixel Output Structures
AMI Semiconductor
– May 06, M-20571-001
www.amis.com
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AMIS-720442-A: 400dpi Contact Image Sensor
5.0 Signal Conversion Circuit
Data Sheet
Figure 5 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 energy of the
switch edge along with the signal current pulses, minimizing the switching patterns on the video pixels. The summed charges stored on
the CAP produce a pixel voltage. This voltage amplitude is proportional to the charge from the current pulse and the value of the CAP.
Figure 5: Video Output Test and Application Circuit
Since switching energies are components with high frequencies, they tend to integrate to a 0 value and the remainder adds a constant
value to off-set the dark level. After the pixel is integrated, the CAP is reset to 0V by activating the shunt switch (SW), that connects the
video line to ground prior to accessing the following pixel element. Figure 6, which depicts a typical pixel voltage waveform, shows that
the shunt time is controlled with CP. SW activation and the reset to the dark reference level of the pixel element storage occur
simultaneously, initializing the pixel for its integration process cycle. The signal pixels Vp(n) is referenced to its dark level as it is seen in
Figure 6.
Figure 6: Single Pixel Video Output
AMI Semiconductor
– May 06, M-20571-001
www.amis.com
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