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2020-5-22
UG2020-11 REF-Vacuum-C101-2ED User Guide
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Negative current range sensing range is 300 mV/op-amp gain/RS1, corresponding to regeneration current
limit in MCEWizard (parameters of RegenLim)
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If 3X ADC internal gain is selected, there is 800 mV range for motoring condition current sensing (3300
mV/3 – 300 mV = 800 mV, and 800 mV/op-amp gain/RS1 is the maximum allowable motor current.
“Motoring current limit * Motor Rated Amps * 1.414” should be below this maximum allowable range,
which is related to input parameters in MCEWizard.
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If 1X ADC internal gain is selected, 3000 mV range for motoring mode current sensing (3300 mV – 300 mV =
3000 mV).
For a better system signal-to-noise ratio (SNR), 6X and 12X internal AD gain is not recommended when there is
an external amplifier. And even for direct AD sensing mode (without external op-amp), whether 12X/6X internal
gain is acceptable or not depends on the ground noise level, or the final motor control performance.
Figure 22
Current feedback configuration in MCEWizard for REF- Vacuum -C101-2ED
6.1.3
Configuration and calculation for direct current sensing
For applications that require minimal hardware costs, direct AD samples can be used, which means, without
external op-amp, and only RC for operational bias and low pass filter, as shown in Figure 23.
Based on the principle of Kirchhoff's voltage law, the real AD input voltage is decided by the divider of R29 &
R34:
