AN1857 Freescale Semiconductor / Motorola, AN1857 Datasheet - Page 10

• Manufacturer Part Number: AN1857
• Description: A 3-Phase ac Induction Motor Control System Based on the MC68HC908MR32
• Manufacturer: Freescale Semiconductor / Motorola

Application Note
Fault Inputs
10
For a better understanding of the control board, a description of some of
its circuits follows.
Two system fault inputs to the control board are designed to protect the
power stage: system bus overvoltage and system bus overcurrent. The
input signals for these fault comparators originate from signals on the
power board. If an optoisolation board is used in the system, these
signals are optocoupled and transparently passed to the control board
as an analog signal.
The comparator circuits provide digital signals to the MR32’s fault 1 and
fault 2 inputs, respectively. These faults, should one or both occur, will
force the PWM generator into a known inactive state, protecting the
power stage outputs.
of the fault inputs. The potentiometer, connected to the inverting (–) input
of the comparator, sets its threshold. When the input from the power
board or optoisolation board exceeds the comparator threshold (voltage
at the inverting input to the comparator), the respective fault input to the
MR32 is driven to a logic 1, triggering a fault input to the PWM generator.
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Freescale Semiconductor, Inc.
Figure 3. MC68HC908MR32 Control Board Block Diagram
For More Information On This Product,
TERMINAL I/F
dc POWER
12–15 Vdc
Three software-controlled LEDs
Motor I/O interface via a ribbon cable connector
On-board regulated power supply
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OVERCURRENT/
OPTO-ISOLATED
OVERVOLTAGE
POWER SUPPLY
REGULATED
INPUTS
RS-232
Figure 4
OPTO/POWER DRIVER I/O CONNECTOR
OUTPUTS (6)
FORWARD/REVERSE
PWM
CONNECTOR
PROCESSOR
STATUS
EMULATOR/
LEDS
START/STOP
is a schematic of the circuit used for both
SWITCH
CURRENT/TEMP
SENSE INPUTS
SWITCH
PWM
LEDS
MISC. PWR AND
CONTROL I/O
SWITCHES
SPEED
OPTION
POT
SWITCH
RESET
BACK-EMF
INPUTS
EFFECT
INPUTS
INPUT
TACH
HALL
40-PIN
CONNECTOR
MOTOROLA
AN1857