ADS-933 Просмотр технического описания (PDF) - Murata Power Solutions
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ADS-933 Datasheet PDF : 8 Pages
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ADS-933
CALIBRATION PROCEDURE
Connect the converter per Figure 2. Any offset/gain
calibration procedures should not be implemented until the
device is fully warmed up. To avoid interaction, adjust offset
before gain. The ranges of adjustment for the circuits in
Figure 2 are guaranteed to compensate for the ADS-933’s
initial accuracy errors and may not be able to compensate for
additional system errors.
A/D converters are calibrated by positioning their digital
outputs exactly on the transition point between two adjacent
digital output codes. This is accomplished by connecting
20kΩ
+5V
–5V
20kΩ
+5V
–5V
+5V
4.7µF
0.1µF
+5V
4.7µF
0.1µF
4.7µF
–5V
0.1µF
0.1µF 4.7µF
6
GAIN
ADJUST
31
+5V
DIGITAL
7,
30
DIGITAL
GROUND
5
OFFSET
ADJUST
38 +5V ANALOG
2, 4, 36
ANALOG
GROUND
37 –5V
ADS-933
34 ENABLE
8 FIFO/DIR
10 FSTAT1
11 FSTAT2
1
+3.2V
REF. OUT
ANALOG INPUT 3
FIFO READ 9
START CONVERT 12
COMP. BITS 35
33 OVERFLOW
32 EOC
29 BIT 1 (MSB)
28 BIT 1 (MSB)
27 BIT2
26 BIT 3
25 BIT 4
24 BIT 5
23 BIT 6
22 BIT 7
21 BIT 8
20 BIT 9
19 BIT 10
18 BIT 11
17 BIT 12
16 BIT 13
15 BIT 14
14 BIT 15
13 BIT 16 (LSB)
+5V
Figure 2. Connection Diagram
Table 2a. Setting Output Coding Selection (Pin 35)
OUTPUT FORMAT
PIN 35 LOGIC LEVEL
Complementary Offset Binary
1
Offset Binary
0
Complementary Two’s Complement
1
(Using MSB, pin 29)
Two’s Complement
0
(Using MSB, pin 29)
LED's to the digital outputs and performing adjustments until
certain LED's "flicker" equally between on and off. Other
approaches employ digital comparators or microcontrollers to
detect when the outputs change from one code to the next.
For the ADS-933, offset adjusting is normally accomplished
when the analog input is 0 minus ½ LSB (–42µV). See Table
2b for the proper bipolar output coding.
Gain adjusting is accomplished when the analog input is at
nominal full scale minus 1½ LSB's (+2.749874V).
Note: Connect pin 5 to ANALOG GROUND (pin 4) for
operation without zero/offset adjustment. Connect pin 6 to
pin 4 for operation without gain adjustment.
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input (pin
12) so that the converter is continuously converting.
2. For zero/offset adjust, apply –42µV to the ANALOG INPUT
(pin 3).
3. Adjust the offset potentiometer until the code flickers
between 1000 0000 0000 0000 and 0111 1111 1111 1111
with pin 35 tied high (complementary offset binary) or
between 0111 1111 1111 1111 and 1000 0000 0000 0000
with pin 35 tied low (offset binary).
4. Two's complement coding requires using BIT 1 (MSB) (pin
29). With pin 35 tied low, adjust the trimpot until the output
code flickers between all 0’s and all 1’s.
Gain Adjust Procedure
1. For gain adjust, apply +2.749874V to the ANALOG INPUT
(pin 3).
2. Adjust the gain potentiometer until all output bits are 0’s and
the LSB flickers between a 1 and 0 with pin 35 tied high
(complementary offset binary) or until all output bits are 1’s
and the LSB flickers between a 1 and 0 with pin 35 tied low
(offset binary).
3. Two's complement coding requires using BIT 1 (MSB)
(pin 29). With pin 35 tied low, adjust the gain trimpot until
the output code flickers equally between 0111 1111 1111
1111 and 0111 1111 1111 1110.
4. To confirm proper operation of the device, vary the applied
input voltage to obtain the output coding listed in Table 2b.
MSB
LSB
1111 1111 1111 1111
LSB "1" to "0"
1110 0000 0000 0000
1100 0000 0000 0000
1000 0000 0000 0000
0111 1111 1111 1111
0100 0000 0000 0000
0010 0000 0000 0000
0000 0000 0000 0001
LSB "0" to "1"
0000 0000 0000 0000
OFFSET BINARY
Table 2b. Output Coding
OUTPUT CODING
MSB
LSB
0000 0000 0000 0000
LSB "0" to "1"
0001 1111 1111 1111
0011 1111 1111 1111
0111 1111 1111 1111
1000 000 000 0000
1011 1111 1111 1111
1101 1111 1111 1111
1111 1111 1111 1110
LSB "1" to "0"
1111 1111 1111 1111
COMP. OFF. BIN.
MSB
LSB
0111 1111 1111 1111
LSB "1" to "0"
0110 0000 0000 0000
0100 0000 0000 0000
0000 0000 0000 0000
1111 1111 1111 1111
1100 0000 0000 0000
1010 0000 0000 0000
1000 0000 0000 0001
LSB "0" to "1"
1000 0000 0000 0000
TWO'S COMP.
MSB
LSB
1000 0000 0000 0000
LSB "0" to "1"
1001 1111 1111 1111
1011 1111 1111 1111
1111 1111 1111 1111
0000 0000 0000 0000
0011 1111 1111 1111
0101 1111 1111 1111
0111 1111 1111 1110
LSB "1" to "0"
0111 1111 1111 1111
COMP. TWO'S COMP.
INPUT
RANGE
±2.75V
+2.749916
+2.749874
+2.062500
+1.375000
0.000000
–0.000084
–1.375000
–2.062500
–2.749916
–2.749958
–2.750000
BIPOLAR
SCALE
+FS –1 LSB
+FS –1 1/2 LSB
+3/4 FS
+1/2 FS
0
–1 LSB
–1/2 FS
–3/4 FS
–FS +1 LSB
–FS + 1/2 LSB
–FS
5
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