PHASE LOCKED LOOPS

2. OUTLINE
•
•
•
•
What is PLL
Functional Blocks of PLL
Block Diagram of PLL
Phase Detector•
•
•
•
•
Phase Detector
Low Pass Filter
Voltage Controlled Oscillator (VCO)
Stages of PLL Operation
Application
OUTLINE

3. What is
• Full form of PLL is ‘Phase Locked Loop
• PLL is a circuit, synchronizing an
oscillator) with a reference or input
in phase.
is PLL?
Loop’.
n output signal (generated by an
ut signal in the frequency as well as

7. Functional Blocks
•Phase Detector
•Low Pass Filter•Low Pass Filter
•Voltage Control Oscil
Blocks of PLL
Oscillator (VCO)

8. Block Diagrram of PLL

9. Capture TransientCapture Transient

10. Stages of PLL
•Free Running Stage: When
detector, then due to VCO, PLL w
output frequency of this stage is
frequency of VCO.frequency of VCO.
•Capture Stage: When a input
detector, then due to feedback
output with respect to input. This st
of PLL Operation
n no input is applied at the phase
works in Free Running Stage. The
is dependent on the free running
put frequency is applied at the phase
mechanism PLL tries to track the
stage is called Capture Stage.

11. Stages of PLL
• Phase
frequency
Locked State: Due
comparision stops as
become equal to the input frequencbecome equal to the input frequenc
Locked State.
PLL Operation
Due to feedback mechanism, the
as soon as the output frequency
equency. This stage is called Phaseequency. This stage is called Phase

14. Phase Dete
A phase detector is basically a compa
frequency f_in with feedback frequ
•
• Comparing the input frequency & o• Comparing the input frequency & o
signal which is basically a Dc voltag
The loop is locked when these two
and have a fixed phase difference.
Basically Phase Detector works as a
•
•
Detector
omparator that compares
equency f_out.
the input
output frequency it provides a erroroutput frequency it provides a error
ge.
o signals are of the same frequency
an Ex-OR gate.

18. NALOG PHASE DETECTOR- SWITCH TYPESWITCH TYPE

19. NALOG PHASE DETECTOR-BALANCED MODULATORBALANCED MODULATOR

20. NALOG PHASE DETECTOR-BALANCED MODULATORBALANCED MODULATOR

21. DIGITAL PHASE DETECTOR

25. Low
filter is used to
Pass
• Low-pass remove
noise from the output of the phase
• Low Pass Filter provides a steady d
input of VCO.input of VCO.
ass Filter
e high frequency components and
phase detector.
dc level voltage which becomes the

26. Voltage C
Oscillator (VCO)
Voltage-controlled oscillator gener
voltage.
The dc level output of a low-pass
the voltage-controlled oscillator (V
•
•
the voltage-controlled oscillator (V
• The VCO frequency is adjusted till
of the input signal.
During this adjustment, PLL goes
capture and phase lock.
•
Controlled
Oscillator (VCO)
rates frequency controlled
filter is applied as control
VCO).
by input
signal to
VCO).
signal to
it becomes equal to the frequency
through three stages-free running,

27. Applications of PLL

28. Voltage Controlled Oscillator (VCO)
A Voltage Controlled Oscillator is an oscillator
(waveforms) with variable frequency. The frequency
the magnitude of the Input voltage.
Voltage Controlled Oscillator (VCO)
oscillator which produces oscillating signals
frequency of this waveform is varied by varying

29. Types of Voltage Controlled Oscillators
Harmonic Oscillators - Sin wave generators
Relaxation Oscillator - saw tooth or triangular formor triangular form

30. Voltage controlled oscillator using LM566 IC
Pin configuration of LM 566
Voltage controlled oscillator using LM566 IC
Pin configuration of LM 566

31. Voltage controlled oscillator using LM566 IC
Pin configuration of LM 566
Voltage controlled oscillator using LM566 IC
Functional Blocks of LM 566

32. on the capacitor charges form 0.25Vcc to 0.5 Vvv
∆𝑣 = 0.25 𝑉𝑐𝑐
acitor s charged through constant current source
∆𝑣
∆𝑡
=
𝑖
𝐶 𝑇
0.25𝑉𝑐𝑐
∆𝑡
=
𝑖
𝐶 𝑇
∆𝑡 =
𝑜. 25𝑉𝑐𝑐 𝐶 𝑇
𝑖
rent through is given by
𝑉 − 𝑉
∆𝑡 =
𝑖
rent through is given by
𝑖 =
𝑉𝑐𝑐 − 𝑉𝑐
𝑅 𝑇
me period is given by T= 2Δt, then the frequency of Oscillation is given by
𝑓𝑜 =
1
𝑇
And further 𝒐
𝟐(𝑽 𝒄𝒄−𝑽 𝒄)
𝑪 𝑻 𝑹 𝑻 𝑽 𝒄𝒄
Circuit Diagram
, then the frequency of Oscillation is given by

33. h no modulating signal input, and if the voltage at pin 5 ia baised to (7/8) V
n Frequency of oscillation is given by
𝒐
𝟐(𝑽 𝒄𝒄−(
𝟕
𝟖
)𝑽 𝒄)
𝑪 𝑻 𝑹 𝑻 𝑽 𝒄𝒄
𝟎.𝟐𝟓
𝑪 𝑻 𝑹 𝑻
(2)
e voltage to frequency conversion factor ‘Kv‘ is given by
𝐾𝑣 =
∆𝑓0
∆𝑣𝑐
(3)
is the modulating input voltage required to generate
frequency shift for VCO.
us Assume f1 is the new frequency due to ‘Δ’ change inus Assume f1 is the new frequency due to ‘Δ’ change in
dulating input vc, then
𝛥𝑓0 = 𝑓1 − 𝑓𝑜
𝒇 𝟏 =
𝟐(𝑽 𝒄𝒄 − [𝑽 𝒄 − ∆𝒗 𝒄])
𝑪 𝑻 𝑹 𝑻 𝑽 𝒄𝒄
(𝟒)
m (1) and (4)
𝟎
𝒄
𝑪 𝑻 𝑹 𝑻 𝑽 𝒄𝒄
h no modulating signal input, and if the voltage at pin 5 ia baised to (7/8) Vc
Circuit Diagram

34. Applications of VCO
•Electronic jamming equipment.
•Production of electronic music, for production
•Phase locked loop.
•Frequency synthesizers, used in communication
•Function generator
•Tone generator
•FM modulation
•Frequency shift keying
•Clock generator
production of different types of noise.
communication circuits.