December 1990 37
Philips Semiconductors Product specification
Phase-locked-loop with lock detector 74HC/HCT7046A
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.
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 synthesizer.
Fig.35 Type 1, second order frequency step response.
012 4
1.6
1.0
0.6
0
0.8
MGA959
3
1.4
1.2
0.4
0.2
5678
ω
n
t
∆ω
(t)
e
∆ω
e
/ω
n
∆Φ
(t)
e
∆Φ
e
/ω
n
−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
