ADCDS-1603
16-Bit, 2.3 Megapixels/Second
CCD Signal Processor
Programmable Analog Bandwidth Function
When interfacing to CCD arrays with very high-speed "read-out" rates,
the ADCDS-1603's input stage must have sufficient analog bandwidth to
accurately reproduce the output signals of the CCD array. The amount of
analog bandwidth determines how quickly and accurately the "Reference
Hold" and the "CDS output" signals will settle . If only a single analog
bandwidth was offered, the ADCDS-1603's bandwidth would be set
to acquire and digitize CCD output signals to 16-bit accuracy, at the
maximum conversion rate of 2.3MHz (434ns see Figure 8 for details).
Applications not requiring the maximum conversion rate would be
forced to use the full analog bandwidth at the possible expense of noise
performance.
The ADCDS-1603 avoids this situation by offering a fully programmable
analog bandwidth function. The ADCDS-1603 allows the user to "bandwidth
limit" the input stage in order to realize the highest level of noise performance
for the application being considered. Table 2 describes recommendations in
selecting the appropriate reference hold (Reference Aquisition Time) and CDS
output (Pixel Data Settling Time) needed for a particular application. Each of
the selections listed in Table 3 have been optimized to provide only enough
analog bandwidth to acquire a full scale input step (Vsat), to 16-bit accuracy,
in a single conversion. Increasing the analog bandwidth (using a faster settling
and acquisition time) would only serve to potentially increase the amount of
noise at the ADCDS-1603's output. The ADCDS-1603 uses a two bit digital
word to select four different analog bandwidths for the ADCDS-1603's input
stage (See Table 2 for details). Table 3 shows typical RMS noise for given
bandwidth and gain settings.
Table 3. RMS Noise
Symbol
T1
Min.
–
–
–
–
–
20
–
–
–
–
–
20
–
–
–
–
–
20
–
–
–
–
–
20
Typ.
434
LO
LO
180
120
50
555
HI
LO
230
205
50
1000
LO
HI
370
520
50
1250
HI
HI
470
680
50
Max.
3
–
–
–
134
140
–
–
–
–
–
140
–
–
–
–
–
140
–
–
–
–
–
140
Units
ns
Parameters
2.3 MHz Conversion
A0
A1
Gain = (pin 4 open)
Gain = 6 (pin 4 - to GND)
2 MHz Conversion
A0
A1
Gain = (pin 4 open)
Gain = 6 (pin 4 - to GND)
1 MHz Conversion
A0
A1
Gain = (pin 4 open)
Gain = 6 (pin 4 - to GND)
800 kHz Conversion
A0
A1
Gain = (pin 4 open)
Gain = 6 (pin 4 - to GND)
Min.
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
Typ.
–
–
1.5
2.1
–
–
1.4
2
–
–
1.3
1.6
–
–
1.2
1.5
Max.
LO
LO
–
–
HI
LO
–
–
LO
HI
–
–
HI
HI
–
–
Units
Table 2. Timing Specification
Parameters
2.3 MHz Conversion
Conversion Time
A0 (pin 30)
A1 (pin31)
Reference Acquisition Time
Pixel Data Settling Time
Start Convert
1.8 MHz Conversion
Conversion Time
A0 (pin 30)
A1 (pin31)
Reference Acquisition Time
Pixel Data Settling Time
Start Convert
1 MHz Conversion
Conversion Time
A0 (pin 30)
A1 (pin31)
Reference Acquisition Time
Pixel Data Settling Time
Start Convert
800 kHz Conversion
Conversion Time
A0 (pin 30)
A1 (pin31)
Reference Acquisition Time
Pixel Data Settling Time
Start Convert
See timing figures 7 and 8.
T2
T3
T4
T1
ns
ns
LSB RMS
LSB RMS
ns
LSB RMS
LSB RMS
T2
T3
T4
T1
ns
ns
LSB RMS
LSB RMS
ns
T2
T3
T4
T1
ns
ns
LSB RMS
LSB RMS
ns
T2
T3
T4
ns
ns
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Technical enquiries
email: sales@murata-ps.com, tel:
+1 508 339 3000
MDA_ADCDS-1603.E06 Page 6 of 11
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