ADS7807 Burr-Brown Corporation, ADS7807 Datasheet - Page 13

• Manufacturer Part Number: ADS7807
• Description: Low-Power 16-Bit Sampling CMOS ANALOG-to-DIGITAL CONVERTER
• Manufacturer: Burr-Brown Corporation

used for each input range (see Figure 8). The input resistor
divider network provides inherent overvoltage protection
guaranteed to at least 25V.
Analog inputs above or below the expected range will yield
either positive full scale or negative full scale digital outputs
respectively. Wrapping or folding over for analog inputs
outside the nominal range will not occur.
CALIBRATION
HARDWARE CALIBRATION
To calibrate the offset and gain of the ADS7807 in hard-
ware, install the resistors shown in Figure 7a. Table VII lists
the hardware trim ranges relative to the input for each input
range.
SOFTWARE CALIBRATION
To calibrate the offset and gain in software, no external
resistors are required. However, to get the data sheet speci-
fications for offset and gain, the resistors shown in Figure 7b
are necessary. See the No Calibration section for more
FIGURE 7a. Circuit Diagrams (With Hardware Trim).
FIGURE 7b. Circuit Diagrams (Without Hardware Trim).
33.2k
+5V
50k
100
66.5k
+5V
100
50k
V
IN
2.2µF
2.2µF
+5V
10V
10V
200
1M
V
IN
2.2µF
2.2µF
+
+
200
1
2
3
4
5
6
R1
AGND1
R2
CAP
REF
AGND2
+
+
1
2
3
4
5
6
IN
IN
R1
AGND1
R2
CAP
REF
AGND2
IN
IN
50k
V
IN
+5V
33.2k
50k
200
100
V
2.2µF
2.2µF
IN
1M
0-5V
0-5V
13
33.2k
200
100
2.2µF
2.2µF
+
+
TABLE VII. Offset and Gain Adjust Ranges for Hardware
details on the external resistors. Refer to Table VIII for the
range of offset and gain errors with and without the external
resistors.
NO CALIBRATION
See Figure 7b for circuit connections. Note that the actual
voltage dropped across the external resistors is at least two
orders of magnitude lower than the voltage dropped across
the internal resistor divider network. This should be consid-
ered when choosing the accuracy and drift specifications of
the external resistors. In most applications, 1% metal-film
resistors will be sufficient.
1
2
3
4
5
6
INPUT RANGE
0 to 5V
0 to 4V
10V
R1
AGND1
R2
CAP
REF
AGND2
+
+
1
2
3
4
5
6
IN
IN
R1
AGND1
R2
CAP
REF
AGND2
IN
IN
Calibration (see Figure 7a).
OFFSET ADJUST
RANGE (mV)
50k
15
4
3
+5V
ADS7807
50k
33.2k
200
100
V
2.2µF
2.2µF
IN
1M
0-4V
0-4V
33.2k
200
100
V
2.2µF
2.2µF
IN
+
+
GAIN ADJUST
RANGE (mV)
1
2
3
4
5
6
+
+
R1
AGND1
R2
CAP
REF
AGND2
1
2
3
4
5
6
IN
IN
60
30
30
R1
AGND1
R2
CAP
REF
AGND2
IN
IN
®