BCM2085 Datasheet, PDF (2/2 Pages) Broadcom Corporation. – 65-nm CMOS DigRF EDGE CELLULAR TRANSCEIVER

Antenna
Switch
1900
1800
900
850
TX_HB
TX_LB
RAMP
DAC
OVERVIEW
XOUT
BCM2085
ADC
ADC
Digital
Filter
DCXO
RXTXDATA
RXTXEN
Calibration
LPF
PFD/CP
LPF
MMD
PFD/CP
MMD
Modulator
Cordic
DigRF
Interface
CTRLDATA
CTRLEN
CTRLCLK
Baseband
STROBE
SYSCLK
SYSCLKEN
BCM2085 Reference Design
The BCM2085 is a 65-nm CMOS single chip quad-band GSM/GPRS/
EDGE RF transceiver for GSM850/EGSM900/DCS1800/PCS1900
voice and data applications. The monolithic die, designed on a 65-nm
pure digital CMOS technology, integrates the transceiver core as well as
the analog functionality to provide a digital interface compliant with the
DigRF v1.12 standard. The BCM2085 offers a low power, highly-
integrated and low cost EDGE RF solution in a 4 mm x 4 mm package.
It is the industry's smallest DigRF-compliant EDGE transceiver.
The BCM2085 delivers outstanding RF performance while achieving
low power consumption through innovative architecture and circuit
design. The RF transceiver draws upon Broadcom's extensive experience
in pure digital CMOS radio design. Proprietary, autonomous, real-time
calibrations within the radio ensure the BCM2085 delivers critical radio
performance while using pure digital CMOS. Integration of the voltage
controlled oscillators, synthesizers, and loop filters minimizes the board
area and external component count.
A novel polar transmit architecture ensures the low transmit power
consumption and eliminates any SAW filters in the transmit path. The
transmitter employs a Σ∆ modulator for GMSK and a polar modulator
for 8PSK. The transmit modulators and ramp generator are also
integrated. This architecture enables the use of standard linear power
amplifiers to accelerate time to market through ease of design while
ensuring a robust manufacturing solution.
The receiver is based on a proven low-IF architecture providing
suppression of DC offsets avoiding the issues related to direct conversion
receivers. Four integrated LNAs permit quad-band implementations.
Digitization of the receive signal is performed with Σ∆ ADCs followed
by internal digital channel filtering.
The BCM2085 features an integrated Σ∆ fractional-N synthesizer to
achieve fast settling times supporting multi-slot GPRS/EDGE operation
up to Class 34. The reference frequency for the synthesizer is supplied
from the internal digitally-controlled crystal oscillator (DCXO) allowing
the use of a low cost crystal. Two buffered reference frequency outputs
are also provided to supply other devices in the system.
Compatible with all DigRF-compliant basebands, the BCM2085 is the
ideal choice to easily lower the cost and size of EDGE handsets and
smartphones.
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2085-PB00-R
01/08/07
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