SKY73025 Datasheet, PDF (3/15 Pages) Skyworks Solutions Inc. – 2300 – 2700 MHz High Gain and Linearity

PRELIMINARY DATA SHEET • SKY73025 DOWNCONVERSION MIXER
Functional Description
The SKY73025 is a high gain diversity mixer, optimized for base
station receiver applications. The device consists of two diversity
channels (A and B), each consisting of a low loss RF balun, high
linearity passive mixer, and a low noise IF amplifier.
Two LO amplifiers (independent of channels A and B) are also
included that allow the SKY73025 to connect directly to the output
of a Voltage Controlled Oscillator (VCO). This eliminates the extra
gain stages needed by most discrete passive mixers. A Single
Pole, Double Throw (SPDT) switch has been included to select
between two different LO inputs for frequency hopping
applications (i.e., GSM).
RF Baluns and Passive Mixer
The RF baluns provide a single ended input, which can easily be
matched to 50 Ω using a simple external matching circuit. The RF
baluns offer very low loss, and excellent amplitude and phase
balance.
The high linearity SKY73025 is a passive, double balanced mixer
that provides a very low conversion loss and an excellent 3^rd
Order Input Intercept Point (IIP3).
Additionally, the balanced nature of the mixer provides for high
port-to-port isolation.
LO Buffers and SPDT LO Switch
The LO buffers allow the input power of the SKY73025 to be in
the range of ±6 dBm. The LO section is optimized for low-side LO
injection. However, each of the two LOs can be driven over a wide
frequency range with only slight degradation in performance.
A high isolation SPDT switch allows the SKY73025 to be used for
frequency hopping applications. This switch provides greater than
45 dB of LO1 to LO2 isolation:
For applications that do not require frequency hopping, LO_SEL is
fixed to one state and the appropriate LO input is used. An internal
pull-down resistor enables the LO2 input.
IF Amplifier
The SKY73025 includes high dynamic range IF amplifiers that
follow the passive mixers in the signal path. The outputs require a
supply voltage connection using inductive chokes. These choke
inductors should be high-Q and have the ability to handle 200 mA
or greater.
A simple matching network allows the output ports to be matched
to a balanced 200 Ω impedance. The IF amplifiers are optimized
for IF frequencies between 50 and 500 MHz. The IF amplifiers can
be operated outside of this range, but with a slight degradation in
performance.
The RIFA and RIFB pins (29 and 17, respectively) can be
connected to external resistors (R1 and R2 – see Figure 3) to
reduce the IF amplifier bias current. When a resistor is connected
to pin 29 (R2), the Channel A IF amplifier current is reduced.
When a resistor is connected to pin 17 (R1), the Channel B IF
amplifier current is reduced. The total amount of current reduced
for Channel A and B IF amplifiers is the amount of mixer current
that is reduced.
Table 2 shows the change in Channel A and/or B amplifier current
from using either of three different external resistors.
For example, if a 10 kΩ resistor is used on pin 29 and a 5.1 kΩ
resistor is used on pin 17, the Channel A IF amplifier current is
reduced by 7 mA and the Channel B IF amplifier current is
reduced by 14 mA. The total mixer current is reduced by 21 mA
(7 mA + 14 mA).
Note that the use of any external resistors on either of these two
pins also degrades IIP3 performance. Skyworks recommends
using external resistors no smaller than 1 kΩ.
LO_SEL Input
High
Low
LO Path Selected
LO1 (pin 19) enabled
LO2 (pin 27) enabled
Electrical and Mechanical Specifications
The absolute maximum ratings of the SKY73025 are provided in
Table 3 and the recommended operating conditions in Table 4.
Electrical characteristics for the SKY73025 are provided in
Table 5.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
200691C • Skyworks Proprietary and Confidential information • Products and Product Information are Subject to Change Without Notice • September 21, 2007
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