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Precision Phase Locked Frequency
Control System
Crystal Oscillator
Programmable Reference Frequency
Dividers
DESCRIPTION
The UC1635 family of integrated circuits was designed for use in preci-
sion speed control of DC motors. An extension to the UC1633 line of
phase locked controllers, these devices provide access to both of the
digital phase detector鈥檚 inputs, and include a reference frequency di-
vider output pin. With this added flexibility, this family of controllers can
be used to obtain phase synchronization of multiple motors.
Phase Detector with Absolute Frequency
A reference frequency can be generated using the device鈥檚 crystal oscil-
Steering
lator and programmable dividers. The oscillator operates using a broad
Separate Divider Outputs and Phase
range of crystals, or, can function as a buffer stage to an external fre-
Detector Input Pins
quency source.
Double Edge Option on the Frequency
The phase detector responds proportionally to the phase error between
Feedback Sensing Amplifier
the detector鈥檚 minus input pin and the sense amplifier output. This
Two High Current Op Amps
phase detector includes absolute frequency steering to provide maxi-
mum drive signals when any frequency error exists. This feature allows
5V Reference Output
optimum start-up and lock times to be realized.
Two op-amps are included that can be configured to provide necessary
loop filtering. The outputs of these op-amps will source or sink in excess
of 16mA, so they can provide a low impedance control signal to driving
circuits.
Additional features include a double edge option on the sense amplifier
that can be used to double the loop reference frequency for increased
loop bandwidths. A 5V reference output can be used to accurately set
DC operating levels.
BLOCK DIAGRAM
UDG-92019
7/97
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