
AD9910
ranges such that f
SYSCLK
falls within the specified range. Figure 33
and Figure 34 summarize these VCO ranges.
Rev. 0 | Page 25 of 60
Figure 33 shows the boundaries of the VCO frequency ranges
over the full range of temperature and supply voltage variation
for all devices from the available population. The implication is
that multiple devices chosen at random from the population and
operated under widely varying conditions may require different
values to be programmed into CFR3<26:24> to operate at the
same frequency. For example, Part A chosen randomly from the
population, operating in an ambient temperature of 10°C with
a system clock frequency of 900 MHz may require CFR3<26:24>
to be set to 100b. Whereas Part B chosen randomly from the
population, operating in an ambient temperature of 90°C with a
system clock frequency of 900 MHz may require CFR3<26:24>
to be set to 101b. If a frequency plan is chosen such that the
system clock frequency operates within one set of boundaries
(as shown in Figure 33), the required value in CFR3<26:24> is
consistent from part to part.
Figure 34 shows the boundaries of the VCO frequency ranges
over the full range of temperature and supply voltage variation
for an individual device selected from the population. Figure 34
shows that the VCO frequency ranges for a single device always
overlap when operated over the full range of conditions.
In conclusion, if a user wants to retain a single default value for
CFR3<26:24>, a frequency that falls into one of the ranges
found in Figure 33 should be selected. Additionally, for any
given individual device the VCO frequency ranges overlap,
meaning that any given device exhibits no gaps in its frequency
coverage across VCO ranges over the full range of conditions.
0
VCO0
VCO1
VCO2
VCO3
VCO4
VCO5
395
495
595
695
(MHz)
795
895
995
FLOW = 400
FHIGH = 460
FLOW = 455
FHIGH = 530
FLOW = 530
FHIGH = 615
FLOW = 760
FHIGH = 875
FLOW = 920
FHIGH = 1030
FLOW = 650
FHIGH = 790
Figure 33. VCO Ranges Including Atypical Wafer Process Skew
335
435
535
635
735
(MHz)
835
935
1035
1135
VCO0
VCO1
VCO2
VCO3
VCO4
VCO5
0
FLOW = 370
FHIGH = 510
FLOW = 420
FHIGH = 590
FLOW = 500
FHIGH = 700
FLOW = 700
FHIGH = 950
FLOW = 820
FHIGH = 1150
FLOW = 600
FHIGH = 880
Figure 34. Typical VCO Ranges
Table 8. VCO Range Bit Settings
VCO SEL BITS (CFR3<26:24>)
000
001
010
011
100
101
110
111
PLL Charge Pump
The charge pump current (I
CP
) is programmable to provide the
user with additional flexibility to optimize the PLL performance.
Table 9 lists the bit settings vs. the nominal charge pump
current.
VCO Range
VCO0
VCO1
VCO2
VCO3
VCO4
VCO5
PLL Bypassed
PLL Bypassed
Table 9. PLL Charge Pump Current
I
CP
(CFR3<21:19>)
000
001
010
011
100
101
110
111
Charge Pump Current
(I
CP
in μA)
212
237
262
287
312
337
363
387
External PLL Loop Filter Components
The PLL_LOOP_FILTER pin provides a connection interface to
attach the external loop filter components. The ability to use
custom loop filter components gives the user more flexibility to
optimize the PLL performance. The PLL and external loop filter
components are shown in Figure 35.