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CT 9000 ® ADV
When the PWM STP STATUS line (U16 pin 10) is high the PWM
output (U16 pin 14) is held low and, therefore, FET Q4 is kept off.
The PWM STP STATUS line is high under the following conditions:
U17 pin 11 is not toggied within 170 ms (this causes fail safe U14
pin 10 to go low), DEAD STOP is low, PRESSURE LIMIT 3 is low,
either SIGN and INJECT are high, but not both.
The following table lists the signal status required to run the motor:
Table 3-2. Motor Signals
Signal Name
Status Required To Run The Motor
PWM CONTROL
> -05V
DEAD STOP
+5V
SIGN
Ov (expel), +5V (fill)
INJECT
+5V (expel), OV (fill)
FAILSAFE
+5V
PRESSURE LIMIT 3
+5V
SAFE RELAY CTL
+5V
Pressure Sensing and Control
Motor current is run through a sensing resistor which generates a
voltage that is proportional to the pressure. This voltage is then
amplified to a usable level and input to both the A/D located on the
CPU board and a hardware pressure limit circuit located on the
motherboard.
There are actually two pressure sensing circuits. One is located on
the primary side of the servo transformer, T1, the second is located
on the secondary side of the servo transformer. The two circuits
are identical with the exception of some resistor values. The fol-
lowing discussion will refer to the pressure sensing circuit on the
secondary side of T1.
When the motor is running, current flows through R19. The voltage
developed across R19 is amplified by two separate operational
amplifier circuits. The first circuit consists of U9, R33 and R36.
The output of U9 pin 1 is input to the A/D, U16 pin 2, located on the
CPU board and into one side of a comparator, U10 pin 4. The
output of the comparator is input to the CPU board. The second
circuit consists of U9, R31 and R35. The output of U9 pin 7 is input
to one side of a comparator, U10 pin 6. The output of this com-
parator is input to the PWM control circuitry. This circuit is referred
to as the hardware pressure limit control.
800961-C
Nov. 2000
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