SKY12228-12LF Datasheet, PDF (2/9 Pages) Skyworks Solutions Inc. – High IIP3, 0.7 to 1.0 GHz Variable Attenuator

DATA SHEET • SKY12228-12LF: VARIABLE ATTENUATOR
8
7
6
5
1
2
3
4
S3218
Figure 2. SKY12228-12LF Pinout – 8-Pin SOIC
(Top View)
Table 1. SKY12228-12LF Signal Descriptions
Pin
Name
Description
Pin
Name
1
I_CONTROL
Control current input (current applied is
nominally equal to the current applied to pin 8)
5
RF_OUT
2
GND
Ground. Must be connected to PCB ground using
lowest possible inductance path.
6
GND
3
GND
Ground. Must be connected to PCB ground using
lowest possible inductance path.
7
GND
4
RF_IN
RF input. Input and output are interchangeable.
8
I_CONTROL
Description
RF output. Input and output are interchangeable.
Ground. Must be connected to PCB ground using
lowest possible inductance path.
Ground. Must be connected to PCB ground using
lowest possible inductance path.
Control current input (current applied is
nominally equal to the current applied to pin 1)
Technical Description
The SKY12228-12LF is comprised of a matched pair of silicon PIN
attenuator diodes and a hybrid coupler. Each of the PIN diodes
terminate a coupled ouptut of the coupler.
The impedance of these diodes is controlled by a current applied
from an external source. At 0 mA bias, the impedance of the
diode is very large. As the impedance of these diodes varies from
a very large magnitude to 50 Ω, the insertion loss between the
input (pin 4) and output (pin 5) ports of the hybrid varies from low
to maximum attenuation. If the bias current is increased beyond
the value that produces a 50 Ω resistance in each diode, the
attenuation between the input and output decreases.
Diodes D1 and D2 are RF terminations, so it is important to
provide the control current to these diodes using low-pass filters.
Each of the filters has a 100 nH series inductor and a shunt
220 pF capacitor. The values of these components are selected
for best DC bypassing and RF blocking of the RF signals present
at the anodes of both diodes.
A 1.6 kΩ resistor serves as a voltage-to-current converter. In the
forward biased state, the DC voltage produced across D1 and D2
is roughly 0.7 V. The total control current to the PIN diodes is
approximated by the following equation:
  _{ICONTROL }
V_CONTROL  0.7
1600
Approximately 50 percent of the control current (ICONTROL) flows
equally through each diode. The forward voltages are very well
matched since both diodes are manufactured on a single die. The
control voltage (VCONTROL) should be varied from 0 V for minimum
attenuation up to a voltage that produces the appropriate current
to force each of the PIN diodes to produce 50 Ω and, therefore,
maximum attenuation.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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April 6, 2015 • Skyworks Proprietary and Confidential Information • Products and Product Information are Subject to Change Without Notice • 202500D