ADS-117
12-Bit, 2MHz, Low-Power Sampling A/D Converters
CALIBRATION PROCEDURE
R2
➀
1. Connect the converter per Figure 3, Figure 4, and Table 1 for the ap-
propriate 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.
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 the pin 18 tied high (straight binary) or between 1111
1111 1111 and 1111 1111 1110 with the pin 18 tied low (complemen-
tary 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 1. 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.
4. To confirm proper operation of the device, vary the precision reference
voltage source to obtain the output coding listed in Table 3.
R1
SIGNAL
INPUT
➀
+15V
5kΩ
50Ω
GAIN
ADJUST
5kΩ
10kΩ
ZERO/
OFFSET
ADJUST
–15V
To Pin19
of ADS-117
➀
For values of R1 and R2 refer to Table 1.
Figure 4. Optional Calibration Circuit
Table 1. Input Connections (using external calibration)
INPUT RANGE
0 +10V, ±5
0 to 5V, ±2.5V
0 to +2.5V, ±1.25V
R1
2
2
2
R2
2
6
14
UNIT
kΩ
kΩ
kΩ
Table 2. Zero and Gain Adjustments
INPUT RANGE
0 to +10V
±5V
ZERO ADJUST
+1/2 LSB
+1.22mV
+1.22mV
GAIN ADJUST
RANGE
+9.9963V
+4.9963V
UNIPOLAR
OPERATION
20 BIPOLAR INPUT
21 +10V REF.
+
0.1μF
4.7μF
12 BIT 1 (MSB)
11
10
9
8
7
6
5
4
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
–15V
4.7μF
+
4.7μF
+15V
+5V
4.7μF
+
0.1μF
0.1μF
24
ADS-117
23
3 BIT 10
2 BIT 11
1 BIT 12 (LSB)
15 EOC
17 ENABLE (1-12)
16 START CONVERT
19 ANALOG INPUT
22
13
+
0.1μF
14
COMP BIN 18
+5V
NOTE: 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.
Figure 3. ADS-117 Connection Diagram
www.murata-ps.com
Technical enquiries
email: sales@murata-ps.com, tel:
+1 508 339 3000
MDA_ADS-117.B01
Page 4 of 6
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