RF2488 View Datasheet(PDF) - RF Micro Devices

Part Name

Description

Manufacturer

RF2488

MULTI-MODE DUAL-BAND LNA MIXER

RF Micro Devices 

Preliminary

RF2488

Detailed Description

The RF2488 is fabricated on a high performance Silicon Germanium process that allows optimization of key RF param-

eters (including noise figure, gain and linearity) for very low current consumption. The RF2488 is packaged in a small 24-

pin, 4mmx4mm, leadless chip carrier. It can be operated on a single supply voltage from 2.7V to 3.3V. To reduce power

consumption the RF2488 has a standby mode that draws less than 10uA.

The RF2488 has two frequency bands of operation. Each is comprised of an LNA and two downconverting mixers with

combined RF inputs, and two separate intermediate frequency outputs. The LNA outputs and mixer RF inputs are typi-

cally connected through an image reject SAW filter, which provides image rejection and out-of-band blocking with low in-

band insertion loss. Either of the two IF outputs can be selected whether operating in low band or high band mode. This

feature allows different IF frequencies and SAW filters to be used for different air interfaces in multi-mode phones. The

modes are selected using the external BAND SEL and IF SEL pins; these can be switched using standard CMOS logic

levels.

LNA

There are two LNA circuits: one for high band and one for low band. They have two gain conditions: high gain and low

gain. The gain state is selected using the external GAIN SEL pin that can be switched with standard CMOS logic levels.

The LNAs require a DC-blocking capacitor at the input and an inductor to ground; the inductor is used to provide addi-

tional input linearity and can be removed if the linearity is not required. The LNA output requires an output match, which

is determined by the input impedance of the IR SAW filter (typically 50Ω). The match must include an inductor to supply

to provide the LNA with a DC path to VCC.

8

In high gain mode, the low band LNA exhibits 18dB of gain combined with a noise figure of <1.4dB and a input IP3 (IIP3)

of 3dB. In low gain mode, the device switches to a highly linear state, with IIP3 in excess of 20dBm and a gain of -9dB

with a current drain of less than 500uA.

In high gain mode, the high band LNA exhibits 17dB of gain combined with a noise figure of <1.7dB and a IIP3 of 2dB.

In low gain mode, the device switches to a highly linear state, with IIP3 in excess of 15dBm and a gain of -6dB with a cur-

rent drain of less than 500uA.

Mixers

The mixers are all single-balanced mixers, with low noise figure, high linearity and high gain. The RF input match can be

tuned for a wide range of RF input frequencies. In low band mode, the match consists of an inductive choke to ground

and a 7Ω to 50Ω step up input match. In high band mode, the match consists of a resonant circuit that provides a DC

choke to ground and a 7Ω to 50Ω step up input match.

The LO input port is internally matched to 50Ω and is internally DC-blocked for easy interface across a wide bandwidth.

The LO input can be driven with signals as low as -9dBm with no performance degradation. The matching of the IF out-

puts is discussed in the applications section.

Rev A0 010905

8-129

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