LMX2604 Datasheet, PDF (1/14 Pages) National Semiconductor (TI) – Triple-band VCO for GSM900/DCS1800/PCS1900

January 2004
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
n On-chip Triple-band RF VCOs
GSM: 880 MHz to 915 MHz
DCS: 1710 MHz to 1785 MHz
PCS: 1850 MHz to 1910 MHz
n On-chip tank circuit
n Low phase noise
— -167 dBc/Hz @ 20 MHz offset in GSM band
— -163 dBc/Hz @ 20 MHz offset in DCS band
— -162 dBc/Hz @ 20 MHz offset in PCS band
n High output power
— +6 dBm in GSM mode
— +6 dBm in DCS and PCS mode
n Low current consumption
— 18 mA in GSM mode
— 15 mA in DCS and PCS mode
n +2.6 V to +3.0 V supply voltage
n 0.25 µm RF CMOS process
n Small 20-pin 4x4 LLP package
Applications
n Transmit VCO for GSM, DCS, and PCS
n Closed loop modulation systems
Functional Block Diagram
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