SKY73112 Datasheet, PDF (6/13 Pages) Skyworks Solutions Inc. – 750-850 MHz High Performance VCO/Synthesizer With Integrated Switch

PRELIMINARY DATA SHEET • SKY73112 VCO/SYNTHESIZER
N = M × 2⁴ + A = 0101000110b (this is the same as N_actual)
Multiply the fractional portion that was removed in the previous
step by 256 and remove the fractional portion of the result to
determine FN:
0.55625 × 256 = 142.4
FN = 142 = 10001110b
Divide FN by 256 to determine the actual fractional part, FN_actual:
FN_actual = 142/256 = 0.5546875
Subtract this result from the fractional portion of (D_Total – 3.5) to
determine the actual fractional modulus extender, ME_actual:
ME_actual = (D_Total – 3.5 – N_actual) – FN_actual
= 0.55625 – 0.5546875
= 0.0015625
Multiply this result by 8388608 (the 23-bit ∆Σ modulator value,
2²³) and remove the fractional portion to determine the value of
ME:
0.0015625 × 8388608 = 13107.2
ME = 13107 = 011001100110011b
N = M × 2⁴ + A = 0011010100b (the value programmed)
Multiply the fractional portion that was removed in the previous
step by 256 and remove the fractional portion of the result to
determine FN:
0.038461538 × 256 = 9.846153728
FN = 9 = 00001001b
Divide FN by 256 to determine the actual fractional part, FN_actual:
FN_actual = 9/256 = 0.03515625
Subtract this result from the fractional portion of (D_Total – 3.5) to
determine the actual fractional modulus extender, ME_actual:
ME_actual = (D_Total – 3.5 – N_actual) – FN_actual
= 0.038461538 – 0.03515625
= 0.003305288
Multiply this result by 8388608 (the 23-bit ∆Σ modulator value,
2²³) and remove the fractional portion to determine the value of
ME:
0. 003305288 × 8388608 = 27726.7653
ME = 27726 = 110110001001110b
Example 2:
A desired synthesizer frequency of 725 MHz is required using a
crystal frequency of 13 MHz and an 8/9 prescaler. Since the
maximum internal reference frequency is 25 MHz, the crystal
frequency does not need to be divided. However, a reference
divider ratio of 2 is used for this example.
Restating Equation 2 as a function of D_Total:
D_Total = (725 × 2)/13 = 111.538461538
Where: RF = 725
R1 = 2
F_REF = 13
Determine N_actual by subtracting 3.5 from D_Total and removing the
fractional portion:
D_Total – 3.5 = 108.038461538
Using Equation 3:
N_actual = 108 = M_actual × P + A_actual
Where: M_actual = 13
P=8
A_actual = 4
M = M_actual = 13 = 001101b (the six MSBs)
A = A_actual = 4 = 0100b (the four LSBs)
Package and Handling Information
Since the device package is sensitive to moisture absorption, it is
baked and vacuum packed before shipping. Instructions on the
shipping container label regarding exposure to moisture after the
container seal is broken must be followed. Otherwise, problems
related to moisture absorption may occur when the part is
subjected to high temperature during solder assembly.
The SKY73112 is rated to Moisture Sensitivity Level 3 (MSL3) at
260 °C. It can be used for lead or lead-free soldering. For
additional information, refer to Skyworks Application Note, PCB
Design and SMT Assembly/Rework Guidelines for MCM-L
Packages, document number 101752.
Care must be taken when attaching this product, whether it is
done manually or in a production solder reflow environment.
Production quantities of this product are shipped in a standard
tape and reel format. For packaging details, refer to the Skyworks
Application Note, Tape and Reel, document number 101568.
Circuit Design Considerations
The following design considerations are general in nature and
must be followed regardless of final use or configuration
1. Paths to ground should be made as short and as low
impedance as possible.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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July 9, 2007 • Skyworks Proprietary and Confidential Information • Products and Product Information are Subject to Change Without Notice • 200736A