ADS-932MM Murata Power Solutions Inc, ADS-932MM Datasheet - Page 5

• Manufacturer Part Number: ADS-932MM
• Description: Analog To Digital Converter
• Manufacturer: Murata Power Solutions Inc

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-932’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
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-932, 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
®
CONNECT for UNIPOLAR MODE
+5V
–5V
®
+5V
4.7µF
4.7µF
4.7µF
0.1µF
6.8µF
0.1µF
0.1µF
0.1µF
4.7µF
Figure 2. Bipolar Connection Diagram
31
7, 30
4, 36
37
10
2
11
1
38
34
8
+5V
+5V ANALOG
FIFO/DIR
FSTAT2
+3.2V
REF. OUT
+5V
DIGITAL
ANALOG
GROUND
ENABLE
FSTAT1
UNIPOLAR
DIGITAL
GROUND
–5V
ADJUST
GAIN
20k
6
–5V
ADS-932
5
+5V
START CONVERT
2. For unipolar or bipolar zero/offset adjust, apply –42µV to the
3. For bipolar inputs, adjust the offset potentiometer until the
4. Two's complement coding requires using BIT 1 (MSB) (pin
Gain Adjust Procedure
1. Apply +2.749874V to the ANALOG INPUT (pin 3).
2. For bipolar inputs adjust the gain potentiometer until all
3. Two's complement coding requires using BIT 1 (MSB)
ANALOG INPUT
OFFSET
ADJUST
20k
COMP. BITS
12) so that the converter is continuously converting.
ANALOG INPUT (pin 3).
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).
For unipolar inputs, adjust the offset potentiometers until all
output bits are 0's and the LSB flickers between 0 and 1 with
Pin 35 tied high (straight binary) or until all bits are 1's and
the LSB flickers between 0 and 1 with pin 35 tied low
(complementary binary).
29). With pin 35 tied low, adjust the trimpot until the output
code flickers between all 0’s and all 1’s.
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).
(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.
FIFO READ
5
–5V
12
35
3
9
33
32
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
+5V
OVERFLOW
EOC
BIT 1 (MSB)
BIT 1 (MSB)
BIT2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12
BIT 13
BIT 14
BIT 15
BIT 16 (LSB)
ADS-932