MM1089 View Datasheet(PDF) - Mitsumi
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MM1089 Datasheet PDF : 9 Pages
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MITSUMI
2. Input voltage range vs gain
Shown in Fig. 5. By switching the range using
the input range switching pin, input from GND
level to VCC level is provided.
3. Voltage gain coefficient K vs Rg
Rs/Rg nearly coincides with the voltage gain,
with a slight difference. This difference is
represented by K, but as Rg changes K also
changes. This relationship is indicated in Fig. 6.
The output from the MM1089 may be passed
through an A/D converter and input to a
microcomputer for offset correction; an example
appears in Fig.7. Here the inputs IN A and IN B are
signal sources with input voltage ranges extending
to GND level, while IN C and IN D are inputs which
extend to VCC level.
1. An analog switch is used to input IN A to both
input pins, the other switches are turned off. A
control output is used to apply the "L" level to
the input range switching pin. Here the output
is VCOM+VOFA, and this is read by the
microcomputer and stored as VA.
2. Next, an analog switch is used to input INC to
both input pins; other switches are turned off.
Here the input range switching pin is set to "H"
by the control output. The output at this time is
VCOM+VOFB, and this is read by the
microcomputer and stored as VB. The above
are preparatory measurements.
3. Analog switches are set so that IN A is at one
input, and IN B at the other; the other switches
are turned off. The control output sets the input
range switching pin to "L" level. Here the
measured value VX1 is the output voltage VO1
less the previously determined VA.
VX1=VO1-VA=(IN A-IN B) GV
4. Analog switches are set to input IN C to one
input pin and IN D to the other; the other
switches are turned off. The input range
switching pin is set "H" by the control output.
The measured value VX2 is the output voltage
VO2 less the previous VB.
VX2=VO2-VB=(IN C-IN D) GV
7. Summary
As explained above, an amplifier which is simple
yet has a high CMR can be configured using the
MM1089.
The MM1089 used together with a CPU equipped
with an internal D/A converter should find a broad
range of applications.
Sensor Amplifier MM1089
[dB]
130
120
110
100
CMR 90
80
70
60
50
24
MM1089
Instrumentation amp final stage
( Rs, Rg error 0.1%
1.0%
)
28 32 36 40 44[dB]
Differential gain
Fig.4. CMR vs differential gain
[dB]
50
40
30
H
H
L
20
L
L : Input range switching pin low
H : Input range switching pin high
10
-2 0 2 4 6 8 10 12 14 16 18 [V]
DC input voltage VICM
Fig.5. Common mode input voltage range
1.00
0.98
0.96
0.94
0.92
0.90
0.88
0.86
100
GV=K Rs/Rg
101
102
Rg
103 [kΩ]
Fig.6. Voltage gain coefficient K vs Rg
Fig.7. Application example
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