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Application Report
SCHA003B - September 2002
CMOS Phase-Locked-Loop Applications Using the
CD54/74HC/HCT4046A and CD54/74HC/HCT7046A
W. M. Austin Standard Linear & Logic
ABSTRACT
Applications of the HC/HCT4046A phase-locked loop (PLL) and HC/HCT7046A PLL with
lock detection are provided, including design examples with calculated and measured
results. Features of these devices relative to phase comparators, lock indicators,
voltage-controlled oscillators (VCOs), and filter design are presented.
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Basic Loop Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Description of the HC/HCT4046A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Phase Comparators (PCs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Operation of Phase Comparator PC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Operation of Phase Comparator PC2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Operation of Phase Comparator PC3 (HC/HCT4046A Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Lock Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
PCPout of the HC/HCT4046A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Lock Detector of the HC/HCT7046A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Voltage-Controlled Oscillator (VCO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
VCO Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
VCO Frequency Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
VCO Parametric Ranges and Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Design Examples With Measured and Calculated Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Design Examples With and Without Offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Example With Offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Example Without Offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Rules of Thumb for Quick Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Tabulated Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Filter Design for the HC/HCT4046A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Loop Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
LPF Using PC1 (Example 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Using PC2 With a Lag-Lead Filter (Example 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Simple LPF Using PC2 (Example 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Simple LPF Using PC2 With Divide-by-N (Example 4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Simple RC LPF Using Frequency Offset and PC2 (Example 5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
1
SCHA003B
LPF Design Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Bibliography and References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Appendix A Phase-Comparator Summary Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Appendix B Loop Parameters and Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Appendix C Basic Program for VCO Frequency Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Appendix D R1, R2, and C1 Values With Calculated fosc PC Solutions From
Equations 3, 4, and 5 (VCC = 6 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Appendix E HC4046A PLL Layout With Simple RC Filter (R3C2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
List of Figures
1 Block Diagram of an HC/HCT4046A in a Typical PLL Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Block Diagram of an HC/HCT4046A With External Loop Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 HC/HCT4046A Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4 HC/HCT7046A Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5 PC1 Average Output Voltage as a Function of Input Phase Difference . . . . . . . . . . . . . . . . . . . . . . . . . 9
6 Typical Waveforms for PLL With PC1 Loop Locked at fo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7 PC2 Average Output Voltage as a Function of Input Phase Difference . . . . . . . . . . . . . . . . . . . . . . . . 11
8 Typical Waveforms for PLL With PC2 Loop Locked at fo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9 PC3 Average Output Voltage as a Function of Input Phase Differences . . . . . . . . . . . . . . . . . . . . . . . 12
10 Typical Waveforms for PLL With PC3 Loop Locked at fo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
11 Lock-Detector Circuitry in the HC/HCT7046A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
12 Waveform at Lock-Detector Capacitor When in Lock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
13 Graph For Determining Value of Lock-Detector Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
14 Waveforms at Lock-Detector Capacitor When Unlocked . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
15 VCO Portion of CD74HC4046A/7046A Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
16 Equivalent HC/HCT4046A Charge Circuit of the VCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
17 HC/HCT4046A VCO Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
18 Current Multiplier Ratio M2 as a Function of R2 Bias Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
19 Mirror Current as a Function of R2 Bias Current, Showing Range of Linearity . . . . . . . . . . . . . . . . . 19
20 Mirror Current as a Function of R1 Bias Current, Showing Range of
Linearity (Pin 9 VCOin = 0.5 VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
21 Mirror Current as a Function of R1 Bias Current, Showing Range of
Linearity (Pin 9 VCOin = 0.95 VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
22 VCO Frequency as a Function of VCOin (Measured and calculated values are shown.
R1 = R2 = 10 kW, C1 = 47 pF, Cs = 6 pF, Tpd = 11 ns at VCC = 5 V,
and Tpd = 15 ns at VCC = 3 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
23 HC/HCT4046A PLL VCO Test Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
24 VCO Frequency as a Function of VCOin, Showing Effects of Different Values of
R1 and R2 (10 kW and 100 kW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2 CMOS Phase-Locked-Loop Applications Using the CD54/74HC/HCT4046A and CD54/74HC/HCT7046A
SCHA003B
25 VCO Frequency and Power-Supply Current as a Function of Operating Voltage
VCC, Showing Effects of Different Values of R2 (5 kW and 10 kW). . . . . . . . . . . . . . . . . . . . . . . . . . . 25
26 VCO Frequency as a Function of VCOin, Showing Effects of Different Values
of R1 and R2 (10 kW and 1 MW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
27 VCO Frequency as a Function of VCOin, Showing Duty-Cycle Control Obtained
by Splitting Capacitor C1 and Controlling the Ratio of C1A and C1B . . . . . . . . . . . . . . . . . . . . . . . . . 27
28 Evaluation Circuit and Waveforms for Data in Figure 27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
29 Forms of LPF and Associated Loop Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
E