SKY74038 Datasheet, PDF (4/12 Pages) Skyworks Solutions Inc. – 2.6 GHz/800 MHz Dual Fractional-N/lnteger-N Frequency Synthesizer

DATA SHEET • SKY74038 FREQUENCY SYNTHESIZER
Phase Detectors and Charge Pumps
The SKY74038 uses a separate charge pump phase detector for
each synthesizer. The IF and RF Phase/Frequency Detector (PFD)
can have a programmable charge pump current from 0.4 mA to
1.6 mA and 120 µA to 480 µA, respectively.
For optimum performance, the divided reference frequency
presented at the phase detector input must not exceed 9 MHz
using the RF 16/17 prescaler synthesizer mode, 15 MHz using the
RF 8/9 prescaler, or 2 MHz for the IF synthesizer mode. The
comparison frequency is also limited by the desired frequency
divided by the minimum divide ratio.
The charge pump can be programmed to a high impedance (Hi-Z)
state for open-loop VCO modulation use.
Lock Detection
The output of the IF/RF dividers (R1, N1, R2, N2) and lock
detectors for both synthesizers can be multiplexed to the LD pin.
When programmed for lock detection, the SKY74038 provides an
active low output to indicate the out-of-lock condition. When
locked, the LD pin is high.
Power Down
The SKY74038 supports a number of power-down modes through
the serial interface. Both IF and RF synthesizer blocks can be
powered down, powered up individually, or both powered up
using the EN bits (see the Synthesizer Register Programming
section of this document). The SKY74038 is enabled at power up
by default.
Synthesizer Register Programming
IF Integer-N Synthesizer. The N2 17-bit divider ratio is
calculated using the following equation:
IF
=
N
2
×
F_{----R----E---F-}
R2
As with all integer-N synthesizers, the minimum step size is
related to the divided reference frequency, F_REF.
RF Fractional-N Synthesizer. The N1 divider ratio is calculated
using the following equation:
RF
=
F_{----R----E---F-}
R1
×
N
1_T
ot
a
l
where: N1_Total = N1 + 3.5 + FN + ME
FN sets the fractional-N modulo up to 256 modulo, as calculated
by the following equation:
FN
=
D₉
⎜⎛
⎝
1
2
⎟⎞
⎠
+
D₈
⎜⎜⎝⎛
1
2²
⎟⎟⎠⎞
+
D₇
⎜⎜⎝⎛
1
2³
⎟⎟⎠⎞
+
... +
D₂
⎜⎜⎝⎛
1
2⁸
⎟⎟⎠⎞
where D_n represents the bit locations within the register field.
The fractional modulo can be extended up to 2²¹ using the modulo
extender (ME), if required, as shown by the following equation:
ME
=
D_{21 ⎜⎜⎝⎛}
1
2⁹
⎟⎟⎠⎞
+
D₂₀
⎜⎜⎝⎛
1
2 ¹⁰
⎟⎟⎠⎞
+
D19_{⎜⎜⎝⎛}
1
2 ¹¹
⎟⎟⎠⎞
+
... +
D₉
⎜⎜⎝⎛
1
2 ²¹
⎟⎟⎠⎞
Because of the way the ∆Σ modulator is implemented in the
SKY74038, the number 3.5 must be added to the division number
to obtain the final division ratio. If the integer field of the N divider
shows a non-integer number, the desired frequency or the
division fraction portion needs to be adjusted.
Sample calculations for two fractional-N applications are shown
in Figure 5.
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 following two product options are available for the SKY74038:
• The SKY74038-13 is rated to Moisture Sensitivity Level 3
(MSL3) at 225 °C. It should only be used with lead solder.
• The SKY74038-21 is rated to MSL3 at 260 °C and can be used
with either lead or lead-free solder.
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.
Electrical and Mechanical Specifications
Signal pin assignments and functional pin descriptions are
specified in Table 1. The absolute maximum ratings of the
SKY74038 are provided in Table 2. The recommended operating
conditions are specified in Table 3 and electrical characteristics
are provided in Table 4.
Table 5 provides the register descriptions. Package dimensions
for the SKY74038 are shown in Figure 6 and tape and reel
dimensions for the 20-pin TSSOP package are shown in Figure 7.
Electrostatic Discharge Information
The SKY74038 is a static-sensitive electronic device. Do not
operate or store near strong electrostatic fields. Take proper ESD
precautions.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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June 4, 2007 • Skyworks Proprietary and Confidential information • Products and Product Information are Subject to Change Without Notice • 101075M