LMX2604

Triple-band VCO for GSM900/DCS1800/PCS1900

General Description

The LMX2604 is a fully integrated VCO (Voltage-Controlled

Oscillator) IC designed for GSM900/DCS1800/PCS1900

triple-band application. The IC is ideal for use in the trans-

mitter modulation loop by providing extremely small form

factor and low phase noise. The IC has two VCOs, one for

GSM and a second for DCS/PCS. The IC has two separate

buffer amplifiers to drive an external high power amplifier,

one for GSM900 band and the other one for DCS1800/

PCS1900 bands. The IC also has a differential buffer ampli-

fier to drive a mixer for the offset PLL.

The resonant circuits of the VCOs are fully integrated in the

chip to ease the application of the IC. The high quality factor

of the embedded tank circuit achieves very low phase noise

characteristics at the VCO output. The only required external

components are a couple of supply bypass capacitors and

matching components.

A control pin for controlling the oscillation frequency is

shared by the two VCOs.

The LMX2604 IC is provided in a 20-pin 4x4 LLP (Leadless

Leadframe package).

Features

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On-chip Triple-band RF VCOs

GSM: 880 MHz to 915 MHz

DCS: 1710 MHz to 1785 MHz

PCS: 1850 MHz to 1910 MHz

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On-chip tank circuit

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Low phase noise

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High output power

— +6 dBm in GSM mode

— +6 dBm in DCS and PCS mode

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Low current consumption

— 18 mA in GSM mode

— 15 mA in DCS and PCS mode

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+2.6 V to +3.0 V supply voltage

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0.25 µm RF CMOS process

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Small 20-pin 4x4 LLP package

Applications

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Transmit VCO for GSM, DCS, and PCS

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Closed loop modulation systems

Functional Block Diagram

20066101

January 2004

© 2004 National Semiconductor Corporation

DS200661

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