Single Supply Phase Locked Loop

This circuit will function accurately over a 10:1 frequency range from 1 kHz to 10 kHz, but will not respond as quickly as the basic wide range phase locked loop (PLL). The reason is the use of the CD4046 frequency detector. When an FIN edge occurs ahead of a F feedback pulse, pin 13 of the CD4046  pulls up on C1 via R1 = 1 kW. This current cannot be controlled or manipulated over as wide a range as “I1” in basic wide range phase locked loop (PLL). As a consequence, the response of this PLL is never as smooth nor fast-settling as the basic PLL, but it is still better behaved than most F-to-V converters. Show a picture schematic :

Q1 = 2N3565 OR 2N3904 HIGH BETA NPN
A1, A2, A3 = 1/4 LM324
ON CD4046, PINS 1, 2, 4, 6, 7, 10, 11, 12 ARE NO CONNECTION
USE STABLE, LOW-T.C. PARTS FOR COMPONENTS MARKED*
VS = 7 TO 15 VDC

As with the basic PLL, the detector feeds a current to be integrated in C1 (and R2 provides the necessary “lead”). A1 acts simply as a buffer for the R1, C1 integrator. A3, optional, can provide a nicely filtered output. And A2 servos Q1, drawing a current out of C6 which is proportional to V2. Here the LM331 acts as a current-to-frequency converter, and F output is precisely proportional to the collector current of Q1. As with the basic circuit, this PLL can be used as a quick and/or quiet F-to-V converter, or as a frequency multiplier. One of the most important uses of an F-to-V is to demodulate the frequency of a V-to-F converter, which may be situated at a high common-mode voltage, isolated by photoisolators, or to recover a telemetered signal. An F-to-V converter of this sort can provide good bandwidth for demodulating such a signal.

Source circuit : hqew.net