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2.13 Back-EMF and Motor Phase Current Sensing
The UNI-3 connector supplies 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
connector 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. 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, JG4, that allow the end user
to select which signal group the DSP's A/D will monitor; reference
Figure 2-11. Back-EMF or Motor Phase Current Sense Signals
2.14 Quadrature Encoder/Hall-Effect Interface
The DSP56F801EVM board contains a Quadrature Encoder/Hall-Effect interface
connected to the DSP's Timer D port signals, TD1 and TD2. The circuit is designed to
accept +3.0V to +5.0V encoder or Hall-Effect sensor inputs. Input noise filtering is
supplied on the input path for the Quadrature Encoder/Hall-Effect interface.
shows the encoder interface.
Motor Phase-Current/Back-EMF Analog Input Selector
BACK_EMF_A
PHASE_A_I_SENSE
BACK_EMF_B
PHASE_B_I_SENSE
BACK_EMF_C
PHASE_C_I_SENSE
Technical Summary
Quadrature Encoder/Hall-Effect Interface
Figure
JG4
1
AN2
2
3
4
5
AN3
6
7
8
AN4
9
2-11.
Figure 2-12
2-17
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