74hct9046a NXP Semiconductors, 74hct9046a Datasheet - Page 35

• Manufacturer Part Number: 74hct9046a
• Description: Pll With Bandgap Controlled Vco
• Manufacturer: NXP Semiconductors

Philips Semiconductors
2003 Oct 30
PLL with band gap controlled VCO
proportional
frequency
Fig.36 Frequency compared to the time response.
to output
(MHz)
3.1
3.0
2.9
2.1
2.0
1.9
e
0
e
/
(t)
n
step input
N stepped from 29 to 30
N stepped from 21 to 20
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.5
0
0
Fig.35 Type 2, second order frequency step response.
= 5.0
1.0
1
1.5
N = 30
2
time (ms)
2.0
= 2.0
MGA952
3
2.5
35
4
= 0.3
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.
Further information
For an extensive description and application example
please refer to “Application note” ordering number
9397 750 00078.
0.5
0.707
1.0
5
6
7
MGA959
n t
8
0
0.2
0.4
0.6
0.8
1.0
0.6
0.4
0.2
74HCT9046A
e
e
/
(t)
Product specification
n