Back-Emf And Motor Phase Current Sensing; Primary Back-Emf Or Motor Phase Current Sense Signals - Motorola 56F805 Hardware User Manual

2.17 Back-EMF and Motor Phase Current Sensing

The primary and secondary UNI-3 connectors supply Back-EMF and Motor Phase
Current signals from the three phases of a motor attached to a motor drive unit. The
Back-EMF signals on the UNI-3 connectors are derived from a resistor divider network
contained in the motor drive unit. These resistors divide down the attached motor's
Back-EMF voltages to a 0 to +3.3V level. In certain instances the Back-EMF signals can
exceed this maximum range. The Motor Phase Current signals are derived from current
sense resistors. Both of these signal groups are then routed to a group of header pins that
allow the end user to select which signal group the device's A/D will monitor. Refer to
for the design of a single channel. The Secondary UNI-3's Back-EMF signals
Figure 2-15
are unbuffered and then routed to a header that contains all of the unconnected Secondary
UNI-3 signals; reference
Figure 2-15. Primary Back-EMF or Motor Phase Current Sense Signals
2-20
Freescale Semiconductor, Inc.
Table 2-9.
BACK_EMF_A
PHASE_A_I_SENSE
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JG14
1
AN2
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3
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