Rainbow Electronics AT77C101B FingerChip™ - Manual (Page 13)

13
AT77C101B
2150A–BIOM–02/02
Figure 8. AT77C101B Block Diagram
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).
Figure 9. Functional Description
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.
2240
8
latches
chip
temperature
sensor
line sel
odd
even
8 lines of 280 columns of pixels
4-bit
ADC
ADC
8
1 dummy column
4
4
amp
chip temperature
stabilization
ACKN
De0-3
Do0-3
output
enable analog
output
OE AVE AVO TPE TPP
1
8
PCLK
RST
clock
reset
column selection
4-bit
8
latches
chip
temperature
sensor
column selection line sel
odd
even
8 lines of 280 columns of pixels
4-bit
ADC
ADC
8
1 dummy column
4
4
amp
De0-3
Do0-3
1 2 3 4
4-bit