MM1089 Ver la hoja de datos (PDF) - Mitsumi
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MM1089 Datasheet PDF : 9 Pages
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MITSUMI
Sensor Amplifier MM1089
Gain Settings
1. By mounting appropriate external Rs and Rg resistances, a subtractive amp can easily be configured with a
gain Gv=K RS/Rg (where K=1 typ.).
Here the precision of RS and Rg affects the gain, but has no inherent effect on CMR.
However, the practical range for the gain is Gv=3 to 100.
2. To determine RS and Rg, first RS is calculated from the maximum required output voltage; then the
equation for the gain Gv=K RS/Rg is used to compute Rg.
The voltage gain coefficient K varies with the value of Rg. For approximate values of K see Fig.1. The larger
the value of RS, the larger is the output offset voltage.
If RS is made small, an advantageous offset voltage is obtained, but if it is too small, an adequate maximum
output voltage is not obtained.
As a rough estimate, when the maximum output voltage is to be 10VP-P, Rs=1000kΩ; if it is to be 5VP-P,
then Rs=500kΩ.
Recommended values: When Rs=1000 kΩ, Gv=100, Rg=9.1kΩ
When Rs=1000 kΩ, Gv=50, Rg=18kΩ
When Rs=500kΩ, Gv=50, Rg=9.1kΩ
When Rs=500kΩ, Gv=10, Rg=47kΩ
3. The output offset voltage ratings in the table of electrical characteristics are for Rg=10kΩ, Rs=1000kΩ.
When using other constants, use the following formula for the output offset:
Output offset=VIO GV+IOO RS
4. The output voltage is essentially the voltage applied to the O.COM (OUTPUT COMMON) pin, output as the
reference level. In actuality, an offset is added to the reference potential and output.
Because the O.COM pin is independent of both amps 1 and 2, offset adjustment is easily accomplished by
shifting the O.COM pin voltage by the amount of the offset.
5. If the input range switching pin is set high, the input voltage range is covered from the VCC level; by
switching it to low, the range extends from GND level.
However, the offsets are different, so care must be taken in continuous switching.
6. The O.COM pin setting voltage range and common-mode input range should be set to voltages between
the minimum and maximum values.
[Voltage gain coefficient K vs. Rg]
1.00
0.98
0.96
0.94
0.92
0.90
0.88
0.86
0.84
100
101
102
Fig. 1 Rg (kΩ)
103
MM1089
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