®
®
ADSD-1402
TECHNICAL NOTES
1. Rated performance requires using good high-frequency
circuit board layout techniques. Connect the digital and
analog grounds to one point, the analog ground plane beneath
the converter. Due to the inductance and resistance of the
power supply return paths, return the analog and digital
ground separately to the power supplies.
3.
Full-Scale (Gain) Adjustments
Set the output of the voltage reference used in step 2 to
the value shown in Table 2.
Table 2. Offset and Gain Adjustments
CALIBRATION PROCEDURE
1. Connect the converter per Figure 3. Apply a pulse of 100
nanoseconds minimum to START CONVERT (pin 11) at a
rate of 200kHz. This rate is chosen to reduce flicker if LED's
are used on the outputs for calibration purposes.
2.
Zero (Offset) Adjustments
Apply a precision voltage reference source between ANA-
LOG INPUT A (pin 1) and SIGNAL GROUND (pin 3), then
adjust the reference source output per Table 2. Adjust trimpot
R2 until the code flickers equally between 10 0000 0000 0000
and 10 0000 0000 0001.
Input
Range
±5V
Offset Adjust
+1/2 LSB
+0.000305V
Gain Adjust
FS – 1�½ LSB
+4.999085V
Adjust the gain trimpot R1 until the output code flickers
equally between 11 1111 1111 1110 and 11 1111 1111 1111
4. Repeat above steps for Analog Input B (Pin 40). Use trimpot
R3 for the zero (Offset) adjustment and trimpot R4 for the
Full-Scale (Gain) adjustment.
5. To confirm proper operation of the device, vary the precision
reference voltage source to obtain the output coding listed in
Table 3.
N+1
400 nSec.
25 nSec. per division
N
START
CONVERT
100 nSec.
EOC
DATA OUT
ENABLE A
325 nSec.
175 nSec.
DATA N VALID
75 nSec.
ENABLE B
Data N A
DATA
A or B OUT
HIGH Z
75 nSec.
Data N B
HIGH Z
HIGH Z
Figure 2. ADSD-1402 Timing Diagram
Table 3. Output Coding
OUTPUT CODING
MSB
LSB
INPUT RANGE
±5V
BIPOLAR
SCALE
11
11
11
10
01
00
00
00
1111
1000
0000
0000
0000
1000
0000
0000
1111 1111
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
0000 0001
0000 0000
+4.999390
+4.250000
+2.500000
±0.000000
–2.500000
–4.250000
–4.999390
–5.000000
+FS – 1LSB
+3/4FS
+1/2FS
0
–1/2FS
–3/4FS
–FS+1LSB
–FS
3
MURATA-PS [ MURATA POWER SOLUTIONS INC. ]
