Apair of 2.4-GHz transceivers from Maxim
Integrated Products exemplifies state-of-theart
design reuse in RF ICs. These zero-IF, RF
transceiver chips both provide an RF-to-baseband
receive path, baseband-to-RF transmit path, voltage-
controlled oscillator (VCO), frequency synthesizer,
crystal oscillator, and baseband/
control interface.
The MAX2830 adds an RF power
amplifier (PA) rated at 17.1 dBm
and a transceive and antenna
diversity switch. It targets
IEEE 802.11g and
b Wi-Fi applications.
The MAX2837, which
delivers 0 dBm to drive
an external PA, primarily
suits WiMAX, WiBro,
and 4G cellular applications.
With either IC,
applications only externally
need an RF bandpass
filter (BPF), crystal,
and a small number of
passive components.
The chips use a sigma-delta
fractional-N RF synthesizer with resolution finer
than 20 Hz, but there is a difference in implementation.
In the MAX2830, the synthesizer includes a
divide-by-1 or a divide-by-2 reference frequency
divider (see the green areas in the figure). The
MAX2837 does not. In the data sheets for both
parts, the MAX2830 lists closed-loop phase-noise
values, and the MAX2837 does not.
A digitally tuned crystal oscillator permits the use of a low-cost
crystal in place of a temperature-compensated crystal oscillator.
The transceiver IC also integrates circuits for on-chip dc offset
cancellation, I/Q error, and carrier-leakage detection circuits. And,
both ICs have on-chip monolithic filters for both the receiver and
transmitter, eliminating the need for external surface-acousticwave
(SAW) filters.
In the MAX2830, those baseband filters are optimized for the
IEEE 802.11g standard and proprietary turbo modes up to 40-
MHz channel bandwidth, suiting them for the full range of
802.11g orthogonal frequency-division modulation (OFDM)
data rates (6 to 54 Mbits/s) and 802.11b quadrature phaseshift
keying (QPSK) and complementary code keying (CCK) data
rates (1 to 11 Mbits/s).
The filters in the MAX2837 support up to 2048-carrier fast
Fourier transform (FFT) OFDM and implement programmable
channel filters for 1.75- to 28-MHz RF channel bandwidths.
Including frequency transient settling, the transceiver requires 2-
μs TX-RX switching time.
The transceiver portion of the MAX2830 operates from 2.7 to
3.6 V, and its PA operates from 2.7 to 4.2 V. It comes in a 7- by 7-
mm, leadless 48-pin TQFN-EP package. Lacking the PA, the
MAX2837 operates from a single 2.7- to 3.6-V supply and comes
in a 6- by 6-mm, leadless, 48-pin TQFN package. The ICs are built
on Maxim's proprietary silicon-germanium biCMOS process.
The MAX2830 starts at $5.97, and the MAX2837 starts at
$8.38, both in lots of 1000 and up. Evaluation kits are available.
Maxim Integrated Products
www.maxim-ic.com