SKY73100-11_09 Datasheet, PDF (9/21 Pages) Skyworks Solutions Inc. – 865-960 MHz High Performance VCO/Synthesizer

DATA SHEET • SKY73100-11 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
976
974
972
970
968
966
964
962
960
958
956
954
952
950
948
946
944
942
940
0
Digital Tune
(VCO Auto-Tuning)
50
100
Analog Tune
150
200
250
300
Time (μs)
350
400
Figure 7. VCO Auto-Tuning @ 960 MHz Frequency Settling
450
500
S1387
VCO Prescalers
The VCO prescalers divide the VCO output signal by either 16/17
or 8/9. The Σ∆ 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
SKY73100-11.
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
Σ∆ 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
200361B • Skyworks Proprietary and Confidential Information • Products and Product Information are Subject to Change Without Notice • April 15, 2009
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