ca3228 Harris Corporation, ca3228 Datasheet - Page 7

• Manufacturer Part Number: ca3228
• Description: Speed Control System With Memory
• Manufacturer: Harris Corporation

to be able to supply vacuum, the gate output must be low. If
the output from the Control Amplifier exceeds 0.573V
vacuum is supplied to the servo unit. If the output of the
Control Amplifier is between 0.573V
vacuum is held in the servo unit and vehicle speed is
maintained. If the output from the Control Amplifier drops
below 0.427V
vacuum is vented.
Overspeed Detector Comparator
The Overspeed Detector circuit is used when the following
sequence of events occur: A speed is set in memory, the
vehicle is manually accelerated (foot pedal) to a higher
speed and then the ACCEL switch is activated.
During vehicle acceleration V
voltage into the memory update comparator. When the
ACCEL command is given, the capacitor at pin 15 rapidly
charges to within 60mV of V
tor output low and starting the fixed acceleration rate from
the present vehicle speed. The 60mV of offset is required to
insure that the output of the overspeed detector is low under
normal operating conditions. Hysteresis is also designed into
the comparator to eliminate noise problems which may
prevent the chip from going into the Acceleration mode.
End of Resume Comparator
The Resume Comparator is used when the following
sequence of events occurs: A speed is set in memory, the
brake applied, causing the vehicle to go to a lower speed,
and the RESUME switch is activated.
CC
or if the gate output is high, the servo unit
S
S
before switching the compara-
voltage is greater than the V
CC
and 0.427V
CC
CA3228
CC
the
M
10-37
,
Activation of the RESUME switch causes a fixed accelera-
tion rate from the lower speed until the capacitor voltage at
pin 15 is equal to the V
the output of the resume comparator insures that noise
doesn’t reset the comparator until V
Align Voltage Source (Pin 17)
The Align Voltage Source is a X1 buffer with an output of
0.5V
Brake Input Comparator (Pin 12)
When the Brake Input exceeds 0.55V
the Standby mode from Cruise.
Minimum Speed Lockout
Assures that the system remains in a Standby mode if
vehicle speed V
revert to the Standby mode if V
the Cruise mode.
Digital Filter for Redundant Brake and Minimum Speed
Lockout
A 4 bit shift register with an all ‘1’s output decode is used to
filter transients and electromagnetic interference. The filter
prevents false signals from putting the system into Standby
from Cruise.
Ramp Oscillator (Pin 5)
The Ramp Oscillator at pin 5 nominally varies between
amplitudes of 4.1V and 6.1V. The discharge rate is
approximately 4X the charge rate. With a capacitor of
0.001 F on pin 5, the nominal oscillator frequency is 50kHz.
CC
.
S
is below 0.183V
M
voltage. A filter circuit contained in
S
CC
drops below 0.183V
PIN
. It causes the system to
CC
actually equals V
, the chip will go into
CC
M
.
in