ADS-927MC-C Murata, ADS-927MC-C Datasheet - Page 4

• Manufacturer Part Number: ADS-927MC-C
• Description: converter. 5v input range, no pipeline delay, 0 c to +70 c temperature range, rohs compliant....
• Manufacturer: Murata

DATEL
CALIBRATION PROCEDURE (Refer to Figures 2 and 3)
Any offset and/or gain calibration procedures should not be implemented
All fi xed resistors in Figure 2 should be metal-fi lm types, and multiturn
A/D converters are calibrated by positioning their digital outputs exactly
For the ADS-927, offset adjusting is normally accomplished at the point
until devices are fully warmed up. To avoid interaction, offset must be
adjusted before gain. The ranges of adjustment for the circuit of Figure 2
are guaranteed to compensate for the ADS-927's initial accuracy errors
and may not be able to compensate for additional system errors.
potentiometers should have TCR’s of 100ppm/°C or less to minimize drift
with temperature.
on the transition point between two adjacent digital output codes. This can
be accomplished by connecting LED's to the digital outputs and adjusting
until certain LED's "fl icker" equally between on and off. Other approaches
employ digital comparators or microcontrollers to detect when the outputs
change from one code to the next.
where the MSB is a 1 and all other output bits are 0's and the LSB just
changes from a 0 to a 1. This digital output transition ideally occurs when
the applied analog input is +½LSB (+305μV).
®
OFFSET
ADJUST
ZERO/
SIGNAL
INPUT
–15V
+15V
20k :
ADJUST
GAIN
Figure 2. ADS-927 Calibration Circuit
50 :
1.98k :
1.2M :
–12V/–15V
+12V/+15V
+5V
®
4.7—F
4.7—F
0.1—F
4.7—F
+15V
–15V
2k :
• 11 Cabot Boulevard, Mansfi eld, MA 02048-1151 USA • Tel: [phone] • www.datel.com • e-mail: [e-mail]
0 to +10V
+
+
+
4.7—F
0.1—F
0.1—F
0.1—F
Figure 3. Typical ADS-927 Connection Diagram
+
To Pin 20
of ADS-927
13
14
24
19, 23
22
20
21 +10V REF. OUT
DIGITAL
GROUND
ANALOG
INPUT
ANALOG
GROUND
ADS-927
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input (pin 16) so the con-
2. Apply +305μV to the ANALOG INPUT (pin 20).
3. Adjust the offset potentiometer until the output bits are a 1 and all 0's and
Gain Adjust Procedure
1. 1. Apply +4.999085V to the ANALOG INPUT (pin 20).
2. Adjust the gain potentiometer until the output bits are all 1's and the LSB
14-Bit, 1MHz, Low-Power Sampling A/D Converters
Gain adjusting is accomplished when all bits are 1's and the LSB just
changes from a 1 to a 0. This transition ideally occurs when the analog
input is at +full scale minus 1½ LSB's (+4.999085V).
verter is continuously converting. If using LED's on the outputs, a 200kHz
conversion rate will reduce fl icker.
the LSB fl ickers between 0 and 1.
fl ickers between 1 and 0.
Coding is offset binary; 1LSB = 610μV.
CONVERT
MSB
11 1111 1111 1111
11 1000 0000 0000
11 0000 0000 0000
10 0000 0000 0000
01 0000 0000 0000
00 1000 0000 0000
00 0000 0000 0001
00 0000 0000 0000
START
OUTPUT CODING
INPUT VOLTAGE
RANGE
16
±5V
Table 1. Zero and Gain Adjust
LSB
18
17
12
11
10
15
9
8
7
6
5
4
3
2
1
Table 2. Output Coding
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
BIT 13
BIT 14 (LSB)
EOC
ZERO ADJUST
INPUT RANGE
01 Apr 2011 MDA_ADS-927.B02 Page 4 of 8
+½ LSB
+305μV
+4.99939
+3.75000
+2.50000
–2.50000
–3.75000
–4.99939
–5.00000
0.00000
±5V
GAIN ADJUST
+FS –1½ LSB
+4.999085V
BIPOLAR SCALE
+FS –1 LSB
–FS +1 LSB
ADS-927
+3/4 FS
+1/2FS
–1/2FS
–3/4FS
–FS
0