MCP3302(2002) 데이터 시트보기 (PDF) - Microchip Technology
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MCP3302
(Rev.:2002)
(Rev.:2002)
Microchip Technology
MCP3302 Datasheet PDF : 40 Pages
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10 kΩ
1 kΩ
MCP6021
-
VIN
1 µF
+
1 MΩ
VDD = 5V
0.1 µF
IN+
MCP330X
IN-
VREF
1 µF
VOUT VIN
MCP1525
0.1 µF
FIGURE 6-5:
Adding an amplifier allows
for gain and also buffers the input from any high
impedance sources.
This circuit shows that some headroom will be lost due
to the amplifier output not being able to swing all the
way to the rail. An example would be for an output
swing of 0V to 5V. This limitation can be overcome by
supplying a VREF that is slightly less than the common
mode voltage. Using a 2.048V reference for the A/D
converter while biasing the input signal at 2.5V solves
the problem. This circuit is shown in Figure 6-5.
10 kΩ
1 kΩ
MCP606
-
VIN
+
1 µF
1 MΩ
VDD = 5V
0.1 µF
IN+
MCP330X
IN- VREF
10 kΩ
2.048V
1 µF
VOUT VIN
MCP1525
0.1 µF
FIGURE 6-6:
Circuit solution to overcome
amplifier output swing limitation.
MCP3302/04
6.4 Common Mode Input Range
The common mode input range has no restriction and is
equal to the absolute input voltage range: VSS -0.3V to
VDD + 0.3V. However, for a given VREF, the common
mode voltage has a limited swing, if the entire range of
the A/D converter is to be used. Figure 6-7 and
Figure 6-8 show the relationship between VREF and the
common mode voltage swing. A smaller VREF allows for
wider flexibility in a common mode voltage. VREF levels,
down to 400 mv, exhibit less than 0.1 LSB change in
DNL and INL. For characterization graphs that show
this performance relationship, see Figure 2-9 and
Figure 2-12.
VDD = 5V
5
4
4.05V
3
2.8V
2
2.3V
1
0.95V
0
-1
0.25 1.0
2.5
VREF (V)
4.0
5.0
FIGURE 6-7:
Common Mode Input Range
of Full Differential Input Signal versus VREF.
VDD = 5V
5
4
4.05V
3
2.8V
2
2.3V
1
0.95V
0
-1
0.25 0.5
1.25
VREF (V)
2.0
2.5
FIGURE 6-8:
Common Mode Input Range
versus VREF for Pseudo Differential Input.
2002 Microchip Technology Inc.
DS21697B-page 19
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