ADS-112 Datel, Inc., ADS-112 Datasheet - Page 4

• Manufacturer Part Number: ADS-112
• Description: 1mhz, Low-power ADC: 12-bit
• Manufacturer: Datel, Inc.

ADS-112
CALIBRATION PROCEDURE
1. Connect the converter per Figures 3 and 4 and Tables 1 and
2. Zero Adjustments
3. Full-Scale Adjustment
INPUT RANGE
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.
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 flickers 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).
Set the output of the voltage reference used in step 2 to the
value shown in Table 2. Adjust the gain trimming potentiom-
eter 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.
0 to +10V
±5v
Table 1. Input Range Selection
OPERATION
BIPOLAR
21
20
INPUT PIN
+15V
–15V
+5V
Pin 19
Pin 19
4.7µF
4.7µF
4.7µF
0.1µF
OPERATION
UNIPOLAR
+
+
+
4.7µF
0.1µF
0.1µF
0.1µF
TIE TOGETHER
Pin 20 to Ground
Figure 3. Typical ADS-112 Connection Diagram
Pin 20 to Pin 21
+
20
24
23
22
21 +10V REF.
14
13
Note: Always bypass pin 21 to ground
ADS-112
4
0 to +2.5V, ±1.25V
INPUT RANGE
0 to +10V
0 to 5V, ±2.5V
0 to 10V, ±5
Range
COMP BIN
±5V
Input
Table 3. Input Range (using external calibration)
SIGNAL
INPUT
Figure 4. Optional Calibration Circuit
Table 2. Zero and Gain Adjust
18
5k
R1
ADJUST
For values of R1 and R2 refer to Table 3.
GAIN
50
5k
Zero Adjust
+1/2 LSB
12
11
10
15
17
16
19
+1.22mV
+1.22mV
9
8
7
6
5
4
3
2
1
+5V
BIT 1 (MSB)
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12 (LSB)
EOC
ENABLE (1-12)
START CONVERT
ANALOG INPUT
R1
2
2
2
OFFSET
ADJUST
+15V
ZERO/
10k
R2
®
R2
14
–15V
2
6
+FS – 1 1/2 LSB
Gain Adjust
+9.9963V
+4.9963V
To Pin19
of ADS-112
UNIT
k
k
k
®