4/97

•

Precision Phase Locked Frequency

Control System

•

Crystal Oscillator

•

Programmable Reference Frequency

Dividers

•

Phase Detector with Absolute Frequency

Steering

•

Digital Lock Indicator

•

Double Edge Option on the Frequency

Feedback Sensing Amplifier

•

Two High Current Op-Amps

•

5V Reference Output

Phase Locked Frequency Controller

UC1633

UC2633

UC3633

FEATURES

The UC1633 family of integrated circuits was designed for use in phase

locked frequency control loops. While optimized for precision speed

control of DC motors, these devices are universal enough for most ap-

plications that require phase locked control. A precise reference fre-

quency can be generated using the device’s high frequency oscillator

and programmable frequency dividers. The oscillator operates using a

broad range of crystals, or, can function as a buffer stage to an external

frequency source.

The phase detector on these integrated circuits compares the refer-

ence frequency with a frequency/phase feedback signal. In the case of

a motor, feedback is obtained at a hall output of other speed detection

device. This signal is buffered by a sense ampilfier that squares up the

signal as it goes into the digital phase detector. The phase detector re-

sponds proportionally to the phase error between the reference and the

sense amplifier output. This phase detector includes absolute fre-

quency steering to provide maximum drive signals when any frequency

error exists. This feature allows 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 the op-amps will source or sink in excess

of 16mA, so they can provide a low impedence 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 digital lock signal is provided that indicates when

there is zero frequency error, and a 5V reference output allows DC op-

erating levels to be accurately set.

DESCRIPTION

BLOCK DIAGRAM

1