used for each input range (see Figure 8). The input resistor
divider network provides inherent over-voltage protection to
at least ±5.5V for R2IN and ±12V for R1IN.
OFFSET ADJUST
RANGE (mV)
GAIN ADJUST
RANGE (mV)
INPUT RANGE
±10V
±15
±4
±60
±30
±30
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.
0 to 5V
0 to 4V
±3
TABLE VI. Offset and Gain Adjust Ranges for Hardware
Calibration (see Figure 7a).
CALIBRATION
HARDWARE CALIBRATION
are necessary. See the No Calibration section for more
details on the external resistors. Refer to Table VIII for the
range of offset and gain errors with and without the external
resistors.
To calibrate the offset and gain of the ADS7807 in hardware,
install the resistors shown in Figure 7a. Table VI lists the
hardware trim ranges relative to the input for each input
range.
NO CALIBRATION
Figure 7b shows 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-
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
±10V
0V-5V
0V-4V
33.2kΩ
200Ω
1
2
3
4
5
6
200Ω
1
R1IN
VIN
R1IN
1
2
3
4
5
6
R1IN
200Ω
2
3
4
5
6
33.2kΩ
AGND1
R2IN
AGND1
R2IN
VIN
AGND1
R2IN
VIN
100Ω
50kΩ
100Ω
+5V
100Ω
+5V
CAP
33.2kΩ
CAP
+
+
+
+
+5V
2.2µF
2.2µF
2.2µF
CAP
+
+
50kΩ
2.2µF
50kΩ
REF
50kΩ
REF
50kΩ
1MΩ
1MΩ
REF
2.2µF
+5V
50kΩ
AGND2
1MΩ
2.2µF
AGND2
AGND2
FIGURE 7a. Circuit Diagrams (With Hardware Trim).
±10V
0V-5V
0V-4V
33.2kΩ
200Ω
200Ω
1
1
2
3
4
5
6
VIN
R1IN
R1IN
1
R1IN
2
3
4
5
6
200Ω
33.2kΩ
AGND1
R2IN
AGND1
R2IN
2
3
4
5
6
VIN
AGND1
R2IN
66.5kΩ
+5V
VIN
100Ω
100Ω
100Ω
CAP
CAP
+
+
+
+
2.2µF
2.2µF
2.2µF
CAP
+
2.2µF
2.2µF
REF
REF
REF
2.2µF
+
AGND2
AGND2
AGND2
FIGURE 7b. Circuit Diagrams (Without Hardware Trim).
ADS7807
SBAS022C
13
www.ti.com
BB [ BURR-BROWN CORPORATION ]
