SKY73121-11 Datasheet, PDF (9/22 Pages) Skyworks Solutions Inc. – 1805 - 1890 MHz High Performance VCO/Synthesizer With Integrated Switch

DATA SHEET • SKY73121-11 VCO/SYNTHESIZER
Word 0
CLK
DATA
D25 D24 D1
D0
LE
LD
Word 1 (Bit [20] low)
D25 D24 D1
D0
Word 2
D25 D24 D1
D0
Word 3
D25 D24 D1
D0
Figure 6. POR Timing Diagram
Word 1 (Bit [20] high)
D25 D24 D1
D0
Phase Settling Time
S1296
1876
1874
1872
1870
1868
1866
1864
1862
1860
1858
1856
1854
1852
1850
1848
1846
1844
1842
1840
0
Digital Tune
(VCO Auto-Tuning)
50
100
Analog Tune
150
200
250
300
Time (μs)
350
400
Figure 7. VCO Auto-Tuning @ 1860 MHz Frequency Settling
450
500
S1805
VCO Prescalers
The VCO prescalers divide the VCO output signal by either 16/17
or 8/9. The 6'modulator determines whether to divide by 16 or
17 in the 16/17 mode, or whether to divide by 8 or 9 in the 8/9
mode. The 8/9 mode provides the best performance for the
SKY73121-11.
N-Counter
The N-counter consists of two asynchronous ripple counters, a
6-bit M-counter and a 4-bit A-counter. The M-counter determines
the counts using the lower division ratio in the prescaler (8 or 16);
the A-counter determines the counts using the upper division ratio
(9 or 17).
The total N-counter divider ratio for the 8/9 mode is 56 (8 × 7)
minimum; for the 16/17 mode, the ratio is 240 (16 × 15)
minimum.
By changing the counter setting at each reference clock cycle, the
Modulated Fractional Divider (MFD) achieves the desired noise
shaping.
VCO MFD Block
The MFD block divides down the prescaler output to the Phase
Locked Loop (PLL) reference frequency. A third order cascaded
6'modulation technique minimizes spurs through randomization
of the division ratio.
The MFD block controls the division ratio by dynamically
programming the M and A counters in the N-counter.
Phase Detector and Charge Pump
The phase detector and charge pump detect and integrate the
phase and frequency errors of the divided down VCO output
versus the reference clock. This results in a feedback adjustment
of the control voltage for the VCO.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
200888B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • December 1, 2009
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