Datasheet

1997 Nov 25 32
Philips Semiconductors Product specification
Phase-locked-loop with VCO 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.
Fig.33 Type 2, second order frequency step response.
full pagewidth
012 4
1.6
1.0
0.6
0
0.8
MSB740
3
1.4
1.2
0.4
0.2
5678
ω
n
t
0.6
0
0.4
1.0
0.2
0.4
0.2
0.6
0.8
= 5.0
ζ
0.5
0.707
1.0
= 0.3
ζ
= 2.0
ζ
∆Θ
e
/ω
n
∆Θ
e
(t)
∆ω
e
/ω
n
∆ω
e
(t)
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.
Fig.34 Frequency compared to the time response.