LMX5251 Datasheet, PDF (13/40 Pages) Texas Instruments – LMX5251 Bluetooth™ CMOS Radio

www.ti.com
LMX5251
SNOSCW3A – FEBRUARY 2004 – REVISED APRIL 2013
Figure 6. Transmitter Return Loss
FUNCTIONAL DESCRIPTION
The LMX5251 is a high performance, monolithic, radio transceiver optimized for Bluetooth communications
systems. When used in conjunction with a Bluetooth baseband controller (e.g., LMX5100), a complete Bluetooth
node with a Host Control Interface (HCI) can be implemented.
The LMX5251 radio architecture allows for minimal external components. The highly integrated design includes
the low noise amplifier (LNA), mixer, on-chip filters, 2.5 GHz ΔΣ PLL, voltage controlled oscillator (VCO), power
amplifier (PA) driver, and modem functions. Digital modulation and demodulation techniques are utilized for a
robust manufacturable design. Power management includes control over individual chip functions and internal
voltage regulation for optimum performance.
The LMX5251 is optimized for low power operation, while maintaining sensitivity performance. The main external
components required consist of a crystal (or other clock source) and assorted de-coupling capacitors to form a
complete Class 2 Bluetooth radio transceiver. Optional components, based on the requirements of a particular
application may include a band select filter, T/R switch, and a differential to single ended balun (discrete or
microstrip). The T/R switch and balun are required only if one antenna is used instead of two antennas.
Radio Receiver
The signal path of the RX architecture contains an internal LNA and quadrature RF downconverting mixer at 2.5
GHz. A low intermediate frequency (IF) receiver provides high performance at low cost and low current
consumption. The IF demodulator is implemented digitally in combination with a limiting amplifier.
Low Noise Amplifier
The on-board low noise amplifier (LNA) is a single-ended structure designed with a 50Ω input impedance for
simple capacitive matching. The LNA is closely integrated with the mixer providing low noise and good immunity
from blocking signals.
Copyright © 2004–2013, Texas Instruments Incorporated
Product Folder Links :LMX5251
Submit Documentation Feedback
13