74HC4046A Datasheet, PDF (32/34 Pages) NXP Semiconductors – Phase-locked-loop with VCO

Philips Semiconductors
Phase-locked-loop with VCO
Product specification
74HC/HCT4046A
Fig.32 Frequency synthesizer.
note
For an extensive description and application example
please refer to application note ordering number
9398 649 90011.
Also available a computer design program for PLL’s
ordering number 9398 961 10061.
1.6
full pagewidth
1.4
∆ω_e (t)
∆ω_e/ω_{n 1.2}
1.0
ζ= 5.0
0.8
ζ= 2.0
ζ= 0.3
0.5
0.707
1.0
MSB740
0.6
0.4
∆Θ_e (t)
0.2 ^{∆Θe/ωn}
0
0.2
0.6
0.4
0.4
0.6
0.2
0.8
0
1.0
0
1
2
3
4
5
6
7 _ωnt 8
Fig.33 Type 2, second order frequency step response.
Since the output frequency is proportional to the VCO
control voltage, the PLL frequency response can be
observed with an oscilloscope by monitoring pin 9 of the
VCO. The average frequency response, as calculated by
the Laplace method, is found experimentally by smoothing
this voltage at pin 9 with a simple RC filter, whose time
constant is long compared to the phase detector sampling
rate but short compared to the PLL response time.
1997 Nov 25
Fig.34 Frequency compared to the time response.
32