ADS-112
12-Bit, 1MHz, Low-Power Sampling A/D Converters
CALIBRATION PROCEDURE
1.
Connect the converter per Figures 3 and 4 and Tables 1 and 3 for the
appropriate input range. Apply a pulse of 150 nanoseconds to the START
CONVERT input (pin 16) at a rate of 250kHz. This rate is chosen to reduce
the flicker if LED’s are used on the outputs for calibration purposes.
2. Zero Adjustments
Apply a precision voltage reference source between the amplifier’s analog
input and ground. Adjust the output of the reference source per Table 2.
For unipolar, adjust the zero trimming potentiometer so that the output
code flickers equally between 0000 0000 0000 and 0000 0000 0001 with
COMP BIN (pin 18) tied high (straight binary) or between 1111 1111 1111
and 1111 1111 1110 with pin 18 tied low (complementary binary).
For bipolar operation, adjust the potentiometer such that the code flick-
ers equally between 1000 0000 0000 and 1000 0000 0001 with pin 18
tied high (offset binary) or between 0111 1111 1111 and 0111 1111
1110 with pin 18 tied low (complementary offset binary).
3. Full-Scale Adjustment
Set the output of the voltage reference used in step 2 to the value shown
in Table 2. Adjust the gain trimming potentiometer so that the output
code flickers equally between 1111 1111 1110 and 1111 1111 1111 for
pin 18 tied high or between 0000 0000 0001 and 0000 0000 0000 for
pin 18 tied low.
To confirm proper operation of the device, vary the precision reference
voltage source to obtain the output coding listed in Table 4.
Table 1. Input Range Selection
Input Range
±5v
0 to +10V
Input Pin
Pin 19
Pin 19
Tie Together
Pin 20 to Pin 21
Pin 20 to Ground
Input Range
0 to +10V
±5V
SIGNAL
INPUT
R2
+15V
R1
To Pin19
of ADS-112
–15V
5k
50
GAIN
ADJUST
5k
10k
ZERO/
OFFSET
ADJUST
For values of R1 and R2 refer to Table 3.
Figure 4. Optional Calibration Circuit
Table 2. Zero and Gain Adjust
Zero Adjust
+1/2 LSB
+1.22mV
+1.22mV
Gain Adjust
+FS – 1 1/2 LSB
+9.9963V
+4.9963V
Table 3. Input Range (using external calibration)
Input Range
0 to 10V, ±5
0 to 5V, ±2.5V
0 to +2.5V, ±1.25V
R1
2
2
2
R2
2
6
14
Unit
kW
kW
kW
BIPOLAR
OPERATION
20
21
UNIPOLAR
OPERATION
20
21 +10V REF.
+
0.1F
4.7F
–15V
4.7F
4.7F
+15V
+5V
4.7F
+
0.1F
+
0.1F
24
ADS-112
23
22
13
12 BIT 1 (MSB)
11 BIT 2
10 BIT 3
9 BIT 4
8 BIT 5
7 BIT 6
6 BIT 7
5 BIT 8
4 BIT 9
3 BIT 10
2 BIT 11
1 BIT 12 (LSB)
15 EOC
17 ENABLE (1-12)
16 START CONVERT
19 ANALOG INPUT
+
0.1F
14
COMP BIN 18
Note: Always bypass pin 21 to ground
+5V
Figure 3. Typical ADS-112 Connection Diagram
www.murata-ps.com
Technical enquiries
email: sales@murata-ps.com, tel:
+1 508 339 3000
MDA_ADS-112.B01
Page 4 of 6
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