ADS-937
16-Bit, 1MHz Sampling A/D Converters
CALIBRATION PROCEDURE
Connect the converter per Table 1 for the appropriate input
voltage range. 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-937'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-937, offset adjusting is normally accomplished
when the analog input is 0 minus �½LSB (–76.3μV). See Table
2 for the proper bipolar and unipolar output coding.
Gain adjusting is accomplished when the analog input is at
nominal full scale minus 1�½LSB's (–9.999771V for unipolar
and –4.999771V for bipolar).
3. For a bipolar input - Adjust the offset potentiometer until the
output code flickers equally between 1000 0000 0000 0000
and 0111 1111 1111 1111.
For a unipolar input - Adjust the offset potentiometer until all
output bits are 0's and the LSB flickers between 0 and 1.
Gain Adjust Procedure
1. Apply –4.999771V to the ANALOG INPUT (pin 1) for bipolar
gain adjust or apply –9.999771V to pin 1 for unipolar gain
adjust.
2. For a unipolar input - Adjust the gain potentiometer until all
output bits are 1's and the LSB flickers between 1 and 0.
For a bipolar input - Adjust the gain potentiometer until all
output bits are 1's and the LSB flickers between 1 and 0.
3. To confirm proper operation of the device, vary the applied
input voltage to obtain the output coding listed in Table 2.
Table 1. Setting Output Coding Selection (Pin 35)
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input
(pin 16) so that the converter is continuously converting.
2. For unipolar or bipolar zero/offset adjust, apply –76.3μV to
the ANALOG INPUT (pin 1).
INPUT VOLTAGE
RANGE
±5V
0 to -10V
INPUT PIN
Pin 1
Pin 1
TIE TOGETHER
Pins 2 and 3
Pins 3 and 5
Table 2. Output Coding
COMPLEMENTARY BINARY
UNIPOLAR
SCALE
–FS +1 LSB
–7/8 FS
–3/4 FS
–1/2 FS
–1/4 FS
–1/8 FS
–1 LSB
0
INPUT VOLTAGE
0 to -10V
-9.999847
-8.750000
-7.500000
-5.000000
-2.500000
-1.250000
-0.000153
0.000000
COMPLEMENTARY OFFSET BINARY
INPUT RANGE
±5V
+4.999847
+3.750000
+2.500000
+0.000000
-2.500000
-3.750000
-4.999847
-5.000000
BIPOLAR
SCALE
+FS -1 LSB
+3/4 FS
+1/2 FS
0
–1/2 FS
–3/4 FS
–FS +1 LSB
–FS
OUTPUT CODING
MSB
LSB
MSB
LSB
1111 1111 1111 1111
1110 0000 0000 0000
1100 0000 0000 0000
1000 0000 0000 0000
0100 0000 0000 0000
0010 0000 0000 0000
0000 0000 0000 0001
0000 0000 0000 0000
0000 0000 0000 0000
0001 1111 1111 1111
0011 1111 1111 1111
0111 1111 1111 1111
1011 1111 1111 1111
1101 1111 1111 1111
1111 1111 1111 1110
1111 1111 1111 1111
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Technical enquiries
email: sales@murata-ps.com, tel:
+1 508 339 3000
MDA_ADS-937.A01
Page 4 of 8
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