TQ9223C 데이터 시트보기 (PDF) - TriQuint Semiconductor

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TQ9223C

3V Cellular TDMA/AMPS LNA/mixer Receiver IC

TriQuint Semiconductor 

TQ9223C Product Description

The TQ9223C efficiently integrates a low-noise amplifier and

high-intercept mixer, with performance equal to a discrete

implementation, through use of circuit techniques from

monolithic and discrete design practices. The LNA consists of a

common-source amplifier cascoded to a common-gate amplifier

using a DC-stacked topology. The same DC current flows

through both stages. An external noise match is used to

achieve optimum noise figure. LNA input and output matching

is performed with PC boards microstrip lines or lumped-element

surface-mount components, using simple, well understood

networks.

The mixer is implemented as a “cascode”stage operating like a

dual-gate FET mixer. A common-gate LO buffer provides the

necessary gain to drive the mixer FET gate and establishes a

good input match. The on-chip buffer amplifier allows for direct

connection to a commercial VCO at drive levels down to –6dBm.

An “open collector”IF output allows for flexibility, matching to

various IFs and filter types.

The two topologies efficiently use the supply current for low-

power operation, approximately 10mA with a 3V supply. The

overall circuit provides a distinct performance edge over silicon

monolithic designs in terms of input intercept, noise figure and

gain. Specifically, the circuit was intended for use in the

following applications: cellular (AMPS, GSM, JDC, ETACS,

etc.) and ISM band (902 – 928 MHz)

Operation

Please refer to the test circuit above.

Gain Select (Pin 5)

In a strong signal environment, the LNA can be shut down by

applying 0V to pin 5. The result is that the LNA gain decreases

from a nominal of +18dB to –19dB. The current in the LNA

decreases to 1mA. In addition, the input IP3 for the LNA

increases from –6dBm to +5dBm, and for the downconverter

from –11dBm to –7.5dBm.

Power Supply Connection

The TQ9223C was designed to operate within specifications

over the power supply range of 3.0 to 5.5V. The internal biasing

maintains stable operating points with varying supply voltage.

TQ9223C

Data Sheet

Internally, the downconverter has internal capacitance from Vdd

to ground for RF decoupling of the supply line. This should be

augmented with additional decoupling capacitance: 1000pF

connected externally within 5mm of the package pin. A 10-ohm

series resistor in the Vdd line may also be added (optionally) to

provide some filtering of supply line noise. Connections to

ground should go directly to a low-impedance ground plane.

Therefore, it is recommended that multiple via holes to the

ground plane occur within 2mm on the inside of the package.

LNA Input Interfacing (Pin 6)

The TQ9223C LNA was designed for low-noise operation. It

makes use of an optimum noise-matching network at the input,

not a conjugate match, as would be used for maximum power

transfer. Gamma optimum is referenced from the LNA input into

the noise-match network in series with 50 ohms. The gamma

optimum and the noise parameters for selected frequencies are

shown in the LNA Noise Parameters table.

There are several options for the physical realization of gamma

optimum: a series-shunt inductor microstrip transmission line

network or a series capacitor/shunt inductor. The microstrip

transmission lines can easily be constructed on FR-4 or G-10

circuit boards, using standard design techniques. The lumped-

element components are surface-mount elements designed for

RF use. It is important that the board-level circuit establishes an

impedance of gamma optimum, measured at the solder pad of

pin 6. Proper board design for gamma optimum eliminates the

need for tuning adjustments and produces a low-noise circuit,

which is tolerant of component variations.

LNA Out (Pin 9)

The TQ9223C low-noise amplifier requires external output

matching to transform the amplifier's output impedance to the

desired system impedance (typically 50Ω) and to provide a DC

bias path. The recommended output matching circuit is

illustrated in the figure above and consists of a shunt low-Q chip

inductor and a series chip capacitor. The inductor provides a

path for DC current to flow into the amplifier while

simultaneously operating as the first element in the impedance

transforming filter. The series capacitor acts as a block to DC

current and operates as the final element in the impedance

transforming filter.

For additional information and latest specifications, see our website: www.triquint.com

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