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参数资料
| 型号： | FCD4A14CCB |
| 厂商： | ATMEL CORP |
| 元件分类： | 模拟信号调理 |
| 英文描述： | IMAGE SENSOR, UUC19 |
| 封装： | COB-21 |
| 文件页数： | 2/18页 |
| 文件大小： | 426K |
| 代理商： | FCD4A14CCB |
FCD4A14
PRELIMINARY SPECIFICATION
10/18
FUNCTIONAL DESCRIPTION
The circuit is divided into two main sections: sensor and data
conversion. One particular column among 280+1 is selected
in the sensor array (1), then each pixel of the selected column
sends its electrical information to amplifiers (2) (one per line),
then two lines at a time are selected (odd and even) so that
two particular pixels send their information to the input of two
4 bit Analog to Digital Converters (3), so 2 pixels can be read
for each clock pulse (4).
Sensor
Each pixel is a sensor in itself. The sensor detects a
temperature differential between the beginning of acquisition
and the reading of information: this is the integration time.
The integration time begins with a reset of the pixel to a
predefined initial state. Note that the integration time reset
has nothing to do with the reset of the digital section.
Then, at a rate depending on the sensitivity of the pyroelectric
layer, on the temperature variation between the reset and the
end of the integration time, and on the duration of the
integration time, electrical charges are generated at the pixel
level.
Analog–to–Digital Converter / Reconstructing an 8-bit
fingerprint image
An Analog to Digital Converter (ADC) is used to convert the
analog signal coming from the pixel into digital data that can
be used by a processor.
The U.S. Federal Bureau of Investigation requires a 256–
level grey scale image; that is, an 8 bit per pixel resolution.
As the data rate for parallel port and USB is in the range of 1
Megabyte per second, and we need at least a rate of 500
frames per second to reconstruct the image with a fair
sweeping speed for the finger, two 4-bit ADCs have been
used to output 2 pixels at a time on one byte.
Then, as frames are recovered, the reconstruction routine
computes an 8-bit value for each pixel. This value is
calculated from the pixels of each frame coming from the
device, which appear to be at the same place, therefore
reducing noise and increasing resolution.
Start sequence
Although a reset is normally needed only once, after power
up, it is better to reset the FingerChip before each fingerprint
acquisition.
A reset is not necessary between each frame acquisition!
Start sequence must consist of:
1.
Set the RST pin to high
2.
Set the RST pin to low
3.
Send 4 clock pulses (due to pipe-line)
4.
Send clock pulses to skip the first frame.
Note that the first frame never contains relevant information
because the integration time is not correct.
Reading the frames
A frame consists of 280 true columns + 1 dummy column of 8
pixels. As two pixels are output at a time, a system must send
281x4 = 1124 clock pulses to read one frame.
Reset must be low when reading the frames.
Read one byte / output enable
Clock is taken into account on the falling edge and data are
output on the rising edge.
For each clock pulse, after the start sequence, a new byte is
output on the Do0-3, De0-3 pins. This byte contains 2 pixels:
4 bit on Do0-3 (odd pixels), 4 bit on De0-3 (even pixels).
To output the data, the output enable (OE) pin must be low.
When OE is high, the Do0-3 & De0-3 pins are in high
impedance state. This enables an easy connection to a
microprocessor bus without additional circuitry—it will enable
data output by using a chip select signal. Note that the
FCD4A14 is always sending data: there is no data exchange
to perform using read/write mode.
Video output
An analog signal is also available on pins AVE & AVO. Note
that video output is available one clock pulse
before the
corresponding digital output (one clock pipe-line delay for the
analog to digital conversion).
Pixel order
After a reset, pixel number one is located on the upper left
corner, looking at the chip with bond pads to the right. For
each column of 8 pixels, pixels 1-3-5-7 are output on odd
data Do0-3 pins, pixels 2-4-6-8 are output on even data De0-
3 pins. Most significant bit is bit #3, least significant is bit #0.
Synchronisation: the dummy column.
A dummy column has been added to the sensor to act as a
specific pattern to detect the first pixel. So, 280 true columns
+ 1 dummy column are read for each frame.
The 4 bytes of the dummy column contain a fixed pattern on
the two first bytes, and temperature information on the last
two bytes (see later):
even
odd
Dummy Byte 1 DB1:
0000 1111
Dummy Byte 2 DB2:
0000 1111
Dummy Byte 3 DB3:
nnnn rrrr
Dummy Byte 4 DB4:
pppp tttt
The sequence 00001111 00001111 is a very rare sequence
in real fingerprint image, because it means that we have the
sequence ridge/valley/ridge/valley within 4 pixels, that is
200
mm. Moreover, this sequence appears on every frame
(exactly every 1124 clock pulses), so it is an easy pattern to
recognize for synchronization purposes.
Integration time & clock jitter
The FCD4A14 is not very sensitive to clock jitter (clock
variation). The most important requirement is a regular
integration time that ensures the frame reading rate is also as
regular as possible, in order to get consistent fingerprint
slices.
If the integration time is not regular, contrast will vary from
one frame to another.
Note that it is possible to introduce some waiting time
between each set of 1124 clock pulses, but the overall time of
one frame read must be regular. This waiting time is generally
the time needed by the processor to perform some
calculation over the frame (to detect the finger, for instance).
相关PDF资料 |
PDF描述 |
|---|---|
| FCD4A14CC | IMAGE SENSOR, CDIP20 |
| FCD4A14CC | IMAGE SENSOR, CDIP20 |
| FCD4A14CCB | IMAGE SENSOR |
| FCP-101 | 2-OUTPUT 9.6 W AC-DC REG PWR SUPPLY MODULE |
| FCP-031 | 2-OUTPUT 2.9 W AC-DC REG PWR SUPPLY MODULE |
相关代理商/技术参数 |
参数描述 |
|---|---|
| FCD4B14 | 制造商:ATMEL 制造商全称:ATMEL Corporation 功能描述:Thermal Fingerprint Sensor with 0.4 mm x 14 mm Sensing Area and Digital Output |
| FCD4B14CC | 制造商:ATMEL 制造商全称:ATMEL Corporation 功能描述:Thermal Fingerprint Sensor with 0.4 mm x 14 mm Sensing Area and Digital Output |
| FCD4B14CCB | 制造商:ATMEL 制造商全称:ATMEL Corporation 功能描述:Thermal Fingerprint Sensor with 0.4 mm x 14 mm Sensing Area and Digital Output |
| FCD4C1690 | 制造商:n/a 功能描述:Power Semiconductor |
| FCD4N60 | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:600V N-Channel MOSFET |
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