74HCT9046A Datasheet, PDF (35/40 Pages) NXP Semiconductors – PLL with bandgap controlled VCO

Philips Semiconductors
PLL with bandgap controlled VCO
Product specification
74HCT9046A
3.1
proportional
to output
frequency
(MHz) _3.0
2.9
2.1
2.0
MGA952
N = 30
N stepped from 29 to 30
step input
N stepped from 21 to 20
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 with the phase detector
sampling rate but short compared with the PLL response
time.
Further information
For an extensive description and application example
please refer to “Application note” ordering number
9398 649 90011. Also available a “Computer design
program for PLLs” ordering number 9398 961 10061.
1.9
0
0.5 1.0 1.5 2.0 2.5
time (ms)
Fig.36 Frequency compared to the time response.
1999 Jan 11
35