SKY72302-21 Datasheet, PDF (11/23 Pages) Skyworks Solutions Inc. – SKY72302-21: Spur-Free, 6.1 GHz Dual Fractional-N Frequency Synthesizer

DATA SHEET • SKY72302-21 FREQUENCY SYNTHESIZER
The Auxiliary Dividend Register controls the fraction part of the
desired fractional-N value and allows an offset of –0.5 to +0.5 to
the auxiliary integer selected through the Auxiliary Divider
Register. As shown in Figure 10, the value to be loaded is:
x Auxiliary Synthesizer Dividend = Ten-bit value for the auxiliary
synthesizer dividend.
General Synthesizer Registers
The dual-programmable reference frequency dividers provide the
reference frequencies to the phase detectors by dividing the
crystal oscillator frequency. The lower five bits hold the reference
frequency divide index for the main phase detector. The next five
bits hold the reference frequency divide index for the auxiliary
phase detector. Divide ratios from 1 to 32 are possible for each
reference frequency divider (see Tables 2 and 3).
The Reference Frequency Dividers Register configures the dual-
programmable reference frequency dividers for the main and
auxiliary synthesizers. As shown in Figure 11, the values to be
loaded are:
x Main Reference Frequency Divider Index = Desired main
oscillator frequency division ratio –1. Default value on power-up
is 0, signifying that the reference frequency is not divided for
the main phase detector.
x Auxiliary Reference Frequency Divider Index = Desired auxiliary
oscillator frequency division ratio –1. Default value on power-up
is 0, signifying that the reference frequency is not divided for
the auxiliary phase detector.
A3 A2 A1 A0 11 10 9 8 7 6 5 4 3 2 1 0
0 1 0 0 X X MSB
LSB
Auxiliary Synthesizer Dividend
C1421
Figure 10. Auxiliary Dividend Register (Write Only)
Table 2. Programming the Main Reference Frequency Divider
Decimal
Bit 4 (MSB)
Bit 3
Bit 2
0
0
0
0
1
0
0
0
2
0
0
0
—
—
—
—
—
—
—
—
—
—
—
—
31
1
1
1
Bit 1
Bit 0 (LSB)
Reference Divider
Ratio
0
0
1
0
1
2
1
0
3
—
—
—
—
—
—
—
—
—
1
1
32
Table 3. Programming the Auxiliary Reference Frequency Divider
Decimal
Bit 9 (MSB)
Bit 8
Bit 7
0
0
0
0
1
0
0
0
2
0
0
0
—
—
—
—
—
—
—
—
—
—
—
—
31
1
1
1
Bit 6
Bit 5 (LSB)
Reference Divider
Ratio
0
0
1
0
1
2
1
0
3
—
—
—
—
—
—
—
—
—
1
1
32
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
101216L • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • September 9, 2009
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