74HCT9046A Datasheet, PDF (37/43 Pages) NXP Semiconductors – PLL with bandgap controlled VCO

NXP Semiconductors
74HCT9046A
PLL with band gap controlled VCO
3.1
proportional
to output
frequency
(MHz)
2.9
2.1
2.0
mga952
N = 30
N stepped from 29 to 30
step input
N stepped from 21 to 20
1.9
0
0.5 1.0 1.5 2.0 2.5
time (ms)
Fig 36. Frequency compared to the time 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 VCO_IN of the VCO.
The average frequency response, as calculated by the Laplace method, is found
experimentally by smoothing this voltage at pin VCO_IN 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.
13.3 Further information
For an extensive description and application example please refer to “Application note”
ordering number 9397 750 00078.
74HCT9046A_6
Product data sheet
Rev. 06 — 15 September 2009
© NXP B.V. 2009. All rights reserved.
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