TQ5M31 View Datasheet(PDF) - TriQuint Semiconductor
Part Name
Description
Manufacturer
TQ5M31 Datasheet PDF : 16 Pages
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TQ5M31
Data Sheet
General Description
TQ5M31 is a general purpose RFIC mixer downconverter
designed for multiple applications. The mixer is implemented
with a single common-source GaAs MESFET and is designed
to operate with supply voltages from 1.8 to 5 Volts. To use the
TQ5M31, tuning components must be selected for the LO
buffer amplifier and the mixer IF port. An external shunt
inductor on the output of the LO Buffer is needed to resonate
with on-chip capacitance to shape the frequency response
and roll off unwanted noise which might otherwise be injected
into the mixer. The "open-drain" IF output allows for flexibility
in matching to various IF frequencies and filter impedances.
Access to the GIC pin allows flexibility in Gain, Third Order
Intercept, and Power Supply Current. By configuring the GIC
pin with one or two external resistors and a capacitor, the part
can be used in a wide variety of wireless receiver systems.
The TQ5M31 is in a miniature, low cost, 6 lead package
(SOT-23-6). Total dimensions are 2.9 by 2.8 mm with a height
of 1.14 mm.
The LO and RF ports have internal DC blocking capacitors
and are internally matched to 50Ω . This simplifies the design
and keeps the number of external components to a minimum.
Applications
Please refer to the above applications circuit.
LO Buffer Tune (Pin 1)
The broadband input match of the LO buffer amplifier, may
cause thermal and induced noise at other frequencies to be
amplified and injected directly into the LO port of the mixer.
Noise at the IF frequency, and at (LO +/- IF) frequency will be
downconverted and emerge at the IF port, degrading the
downconverter noise figure.
The output node of the L0 buffer amplifier is brought out to Pin
1 and connected to a shunt inductor to ground. This inductor
is selected to resonate with internal capacitance at the L0
frequency in order to roll off out-of-band gain and improve
noise performance. This approach allows selectivity in the L0
buffer amplifier along with the ability to use the TQ5M31 with
multiple applications.
Calculation of Nominal L Value for LO pin
The proper inductor value must be determined during the
design phase. The internal capacitance at Pin 1 is
approximately 1 pF. Stray capacitance on the board
surrounding Pin 1 will add to the internal capacitance, so the
nominal value of inductance can be calculated, but must be
confirmed with measurements on a board approximating the
final layout.
1
2
Ground
3
Ground Placement
is adjusted between
standard inductor values
Figure 3. LO Tuning
The inductor is selected to resonate with the total capacitance
at the LO frequency using the following equation:
L=
1
C(2Π
f
)2
,
where
C = 1.0
pF
Verification of Proper LO Buffer Amp Tuning
Using a Network Analyzer
Procedure:
Connect port 1 of the network analyzer to the L0 input (Pin 3)
of the TQ5M31 with the source power set to -4 dBm. Connect
a coaxial probe to Port 2 of the network analyzer and attach
the probe approximately 0.1 inch away from either Pin 1 or the
inductor. The magnitude of S21 represents the LO buffer
frequency response (figure 4).
12
For additional information and latest specifications, see our website: www.triquint.com
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