CDS-1401 Datel, Inc., CDS-1401 Datasheet - Page 7

• Manufacturer Part Number: CDS-1401
• Description: Fast-settling Correlated Double Sampling Circuit: 14-bit
• Manufacturer: Datel, Inc.

CALIBRATION PROCEDURE
Offset Adjust (Figure 5)
Offset and pedestal errors may be compensated for by
applying external voltages to pin 1 (OFFSET ADJUST V1) and/
or pin 9 (OFFSET ADJUST V2) using either voltage-output
DAC’s or potentiometers configured to appear as voltage
sources.
Offset and pedestal errors may also be compensated for by
applying external currents to pin 2 (OFFSET ADJUST I1) and/
or pin 10 (OFFSET ADJUST I2) by using either current-output
DAC’s or potentiometers configured to appear as current
sources.
1. Connect pin 8 (S/H2 SUMMING NODE) either directly to
2. Tie pins 3 (ANALOG INPUT 1) and 4 (ANALOG INPUT 2)
3. Adjust OFFSET ADJUST V1 or OFFSET ADJUST I1 (while
4. Adjust OFFSET ADJUST V2 or OFFSET ADJUST I2 (while
5. To negate the effect of output droop on the offset-adjust
The sensitivity of the voltage offset adjustments is 100mV per
Volt. The sensitivity of the current offset adjustments is
1V per mA. Pins 1, 2, 9 and 10 should be left open (floating)
when not being used for offset adjustment.
pin 7 (S/H1 ROUT) or through a 200 Ohm potentiometer to
pin 6 (S/H1 OUT).
to pin 5 (ANALOG GROUND).
S/H1 is in the hold mode) until pin 6 (S/H1 OUT) equals 0V.
S/H2 is in the hold mode) until pin 22 (VOUT) equals 0V.
process, each S/H must be continually switched between its
sample and hold modes and adjusted so its output equals
zero immediately after going into the hold mode.
®
200
®
+15V
–15V
+15V
–15V
10
11
12
1
2
3
4
5
6
7
8
9
Figure 5. CDS-1401 Typical Connection Diagram
OFFSET ADJUST V1
OFFSET ADJUST I1
ANALOG INPUT 1
ANALOG INPUT 2
ANALOG GROUND
S/H1 OUT
S/H1 ROUT
OFFSET ADJUST V2
OFFSET ADJUST I2
S/H1 COMMAND
S/H2 COMMAND
S/H2 SUMMING NODE
CDS-1401
7
Gross Offset Adjustment
For gross offset adjustments use pin 2 (OFFSET ADJUST I1)
and/or pin 10 (OFFSET ADJUST I2). All connections made to
pin 2 and pin 10 should be very short because these are very
sensitive points.
Sourcing 1mA into OFFSET ADJUST I1 will cause a –1V offset
change at pin 6 (S/H1 OUT). It will also cause a +1V offset
change at pin 22 (V OUT) if pin 7 (S/H1 ROUT) is connected to
pin 8 (S/H2 SUMMING NODE).
Sourcing 1mA into OFFSET ADJUST I2 will cause a –1V offset
change at pin 22 (V OUT).
Gain Matching Adjustment (Differential Gain)
between S/H1 and S/H2
The user can adjust the gain matching (differential gain)
between S/H1 and S/H2 by leaving pin 7 (S/H1 ROUT) floating
(open) and connecting a 200 Ohm potentiometer between pin
6 (S/H1 OUT) and pin 8 (S/H2 SUMMING NODE). Note, offset
adjustment should take place before gain matching
adjustment.
Apply a full-scale input to both pins 3 (ANALOG INPUT 1) and
4 (ANALOG INPUT 2). Adjust the 200 Ohm potentiometer
(with both S/H's in the sample mode) until pin 22 (V OUT) is
0V.
If gain matching adjustment is not required, leave pin 6 (S/H1
OUT) floating (open) and tie pin 7 (S/H1 ROUT) to pin 8 (S/H2
SUMMING NODE).
–15V ANALOG SUPPLY
+15V ANALOG SUPPLY
+5V DIGITAL SUPPLY
ANALOG GROUND
ANALOG GROUND
ANALOG GROUND
DIGITAL GROUND
A/D CLOCK 1
A/D CLOCK 2
A/D CLOCK 2
A/D CLOCK 1
V OUT
18
24
23
22
21
20
19
17
16
15
14
13
0.1µF
0.1µF
0.1µF
+
+
+
2.2µF
2.2µF
2.2µF
–15V
+15V
+5V
CDS-1401