Si4122 ETC, Si4122 Datasheet - Page 17

• Manufacturer Part Number: Si4122
• Description: DUAL-BAND RF SYNTHESIZER WITH INTEGRATED VCOS FOR WIRELESS COMMUNICATIONS
• Manufacturer: ETC

or
Tables 6 and 7 summarize the characteristics of each
VCO.
As a design example, suppose the goal is to synthesize
frequencies in a 25 MHz band between 1120 MHz and
Figure 15. External Inductance Connection
VCO
RF1
RF2
VCO
RF1
RF2
Table 7. Si4133-BM VCO Characteristics
Table 6. Si4133-BT VCO Characteristics
IF
IF
f
f
947 1720
789 1429
526
947 1720
789 1429
526
Min
Min
CEN
CEN
f
CEN
(MHz)
(MHz)
Range
Range
f
CEN
=
Max
Max
952
952
----------------------------------------------------------------------
2
=
L
L
---------------------------------------------
2
PK G
PK G
L
C
C
2
2
(pF)
(pF)
4.3
4.8
6.5
4.3
4.8
6.5
PKG
NOM
NOM
L
TOT
+
1
1
L
L
L
EXT
(nH)
(nH)
2.0
2.3
2.1
1.5
1.5
1.6
PKG
PKG
C
NOM
C
NOM
L
L
Min
Min
0.0
0.3
2.2
0.5
1.1
2.7
EXT
EXT
(nH)
(nH)
Range
Range
L
12.0
12.5
Max
Max
EXT
4.6
6.2
5.1
7.0
Rev. 1.1
1145 MHz. The center frequency should be defined as
midway between the two extremes, or 1132.5 MHz. The
PLL will be able to adjust the VCO output frequency
±5% of the center frequency, or ±56.6 MHz of
1132.5 MHz (i.e., from approximately 1076 MHz to
1189 MHz). The RF2 VCO has a C
4.1 nH inductance (correct to two digits) in parallel with
this capacitance will yield the desired center frequency.
An external inductance of 1.8 nH should be connected
between RFLC and RFLD as shown in Figure 15. This,
in addition to 2.3 nH of package inductance, will present
the
manufacturing, the external inductance can vary ±10%
of its nominal value and the Si4133 will correct for the
variation with the self-tuning algorithm.
For more information on designing the external trace
inductors, refer to Application Note 31.
Extended Frequency Operation
The Si4133 may operate at an extended frequency
range of 1850 MHz to 2050 MHz by connecting the
RFLA and RFLB pins directly. For information on
configuring
operation, refer to Application Note 41.
Self-Tuning Algorithm
The self-tuning algorithm is initiated immediately
following power-up of a PLL or, if the PLL is already
powered, following a change in its programmed output
frequency. This algorithm attempts to tune the VCO so
that its free-running frequency is near the desired output
frequency. In doing so, the algorithm will compensate
for manufacturing tolerance errors in the value of the
external inductance connected to the VCO. It will also
reduce the frequency error for which the PLL must
correct to get the precise desired output frequency. The
self-tuning algorithm will leave the VCO oscillating at a
frequency in error by somewhat less than 1% of the
desired output frequency.
After self-tuning, the PLL controls the VCO oscillation
frequency. The PLL will complete frequency locking,
eliminating any remaining frequency error. Thereafter, it
will maintain frequency-lock, compensating for effects
caused by temperature and supply voltage variations.
The Si4133’s self-tuning algorithm will compensate for
component value errors at any temperature within the
specified temperature range. However, the ability of the
PLL to compensate for drift in component values that
occur
inductances with temperature coefficients around
±150 ppm/
changes in temperature of approximately ±30
correct
after
o
C, the PLL will be able to maintain lock for
the
self-tuning
total
Si4133
inductance
is
for
limited.
extended
to
NOM
the
Si4133
For
of 4.8 pF. A
VCO.
frequency
o
C.
external
17
In