Specifications

22 DSP56800 Hardware Interface Techniques 
Peripheral Interfaces
4.5 Motor Protection Logic
The DSP56F807EVM contains two UNI-3 connectors that interface with various motor drive boards,
Primary UNI-3 and Secondary UNI-3. The DSP can sense error conditions generated by the motor
power stage boards via signals on the UNI-3 connector. The motor driver board’s Motor Supply DC
Bus Voltage, Current and Motor Phase Currents are sensed on a separate power stage board. The
conditioned signals are transferred to the DSP board via the UNI-3 connector. These analog input
signals are compared to a limit set by trimpots. If the input analog signals are greater than the limit set
by the trimpot, a DSP digital voltage-compatible +3.3V DC fault signal is generated.
4.5.1 Primary UNI-3 Motor Protection Logic
The Primary UNI-3 DC Bus Over-Voltage signal is connected to the DSP’s PWM group A fault
inputs. The three Primary UNI-3 Phase Over-Current signals are connected to the DSP’s PWM group
A’s fault inputs, i.e., FAULTA1, FAULTA2 and FAULTA3. Figure 22 contains the diagram of the
Over-Voltage and one phase of the Phase Over-Current circuit for the UNI-3 interface. The FAULTA1
input can be sourced from the Phase A Over-Current circuit or the DC Bus Over-Current circuit.
Jumper JG1 provides the selection; reference Figure 21 and Table 6.
Figure 21. FAULTA1 Selection Circuit
DC BUS CURRENT SENSE
I_sense_DCB
+
–
+5.0V
+5.0V
LM393
+3.3V
JG1
3
2
1
FAULTA1
+
–
+5.0V
+5.0V
+3.3V
PHA_IS
PHASE A CURRENT SENSE
LM393
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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