ADS-117 Datel, Inc., ADS-117 Datasheet - Page 4

• Manufacturer Part Number: ADS-117
• Description: 2mhz, Low-power ADC: 12-bit
• Manufacturer: Datel, Inc.

ADS-117
CALIBRATION PROCEDURE
1. Connect the converter per Figure 3, Figure 4, and Table 1
2. Zero Adjustments
3. Full-Scale Adjustment
4. To confirm proper operation of the device, vary the precision
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 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
the pin 18 tied high (straight binary) or between 1111 1111
1111 and 1111 1111 1110 with the pin 18 tied low (comple-
mentary 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 1. 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.
reference voltage source to obtain the output coding listed
in Table 3.
+15V
–15V
+5V
4.7µF
4.7µF
4.7µF
0.1µF
OPERATION
UNIPOLAR
+
+
+
0.1µF
0.1µF
4.7µF
0.1µF
+
NOTE:
Figure 3. ADS-117 Connection Diagram
20
24
23
22
21 +10V REF.
13
14
BIPOLAR INPUT
For unipolar operation, ground pin 20.
For bipolar operation, connect pin 20 to pin 21.
Always bypass pin 21 as shown for both unipolar
and bipolar operation.
ADS-117
4
0 to +2.5V, ±1.25V
COMP BIN
INPUT RANGE
0 to +10V
0 to 5V, ±2.5V
Table 1. Input Connections (using external calibration)
0 +10V, ±5
Range
±5V
Input
SIGNAL
INPUT
Figure 4. Optional Calibration Circuit
Table 2. Zero and Gain Adjustments
18
5k
R1
ADJUST
For values of R1 and R2 refer to Table 1.
12
11
10
15
17
16
19
GAIN
50
9
8
7
6
5
4
3
2
1
5k
Zero Adjust
+5V
+1/2 LSB
+1.22mV
+1.22mV
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
ZERO/
+15V
R2
10k
–15V
®
R2
14
2
6
+FS – 1 1/2 LSB
Gain Adjust
+9.9963V
+4.9963V
To Pin19
of ADS-117
UNIT
k
k
k
®