ADS7831 Burr-Brown Corporation, ADS7831 Datasheet - Page 9

• Manufacturer Part Number: ADS7831
• Description: 12-Bit 600kHz Sampling CMOS ANALOG-to-DIGITAL CONVERTER
• Manufacturer: Burr-Brown Corporation

CALIBRATION
The ADS7831 can be trimmed in hardware or software. The
offset should be trimmed before the gain since the offset
directly affects the gain.
Hardware Calibration
To calibrate the offset and gain of the ADS7831, install the
proper resistors and potentiometers as shown in Figure 4a.
The calibration range is 12mV for the offset and 30mV
for full scale.
Potentiometer P
circuit and P
are not critical. R
the value shown. They can easily be made smaller to
provide increased adjustment range. Reducing these below
15% of the indicated values could begin to adversely affect
the operation of the converter.
FIGURE 3. Using CS to Control Conversion and Read Timing.
FIGURE 4a. Circuit Diagram With External Hardware Trim.
NOTE: Use 1% metal film resistors. Trim offset at 0V first, then trim
V
5k
IN
P
gain at 2.5V.
1
+5V
–5V
2
50
and R
5k
P
2
1
1
and R
+5V
and resistor R
2
MODE
BUSY
DATA
the gain adjust circuit. The exact values
BUS
R/C
20k
CS
R
2
1
should not be made any larger than
Acquire
604k
0.1µF
R
10µF
2
1
form the offset adjust
+
t
11
t
1
t
6
t
3
V
AGND1
REF
CAP
AGND2
IN
Convert
t
t
11
7
Hi-Z State
t
4
t
2
9
t
5
P
tion. However, larger resistances will push the useful adjust-
ment range to the edges of the potentiometer. P
probably not exceed 20k
tain reasonable sensitivity.
Software Calibration or No Calibration
The ADS7831 does not require external resistors for its
basic operation. However, the component is designed to be
used with an external 50
specifications apply to this condition. If this resistor is not
used, the only specification that will be affected is total
unadjusted error.
With the 50
teed. Without the 50
range will be 2.46V and the total unadjusted error is not
guaranteed. While it will typically be much less, the total
unadjusted error could be as high as 20LSBs.
FIGURE 4b. Circuit Diagram Without External Hardware Trim.
1
2.5V and the total unadjusted error is 10LSBs guaran-
and P
2
Acquire
t
t
13
can also be made larger to reduce power dissipa-
11
V
IN
resistor, the nominal input voltage range is
Data Valid
50
t
11
t
9
0.1µF
10µF
resistor, the nominal input voltage
HI Z State
and P2 100k
resistor on the input, and the
+
ADS7831
V
AGND1
REF
CAP
AGND2
IN
in order to main-
1
should
®