MAX2831ETM+ Maxim Integrated Products, MAX2831ETM+ Datasheet - Page 32

• Manufacturer Part Number: MAX2831ETM+
• Description: RF Transceiver 2.4GHz to 2.5GHz, 80 2.11g RF Transceiver
• Manufacturer: Maxim Integrated Products

Specifications of MAX2831ETM+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

2.4GHz to 2.5GHz 802.11g/b
RF Transceivers with Integrated PA
The modes of operation for the MAX2831/MAX2832 are
shutdown, standby, transmit, receive, transmitter calibra-
tion, and receiver calibration. See Table 31 for a summa-
ry of the modes of operation. The logic-input pins, SHDN
(pin 12) and RXTX (pin 48), control the various modes.
The MAX2831/MAX2832 feature a low-power shutdown
mode that disables all circuit blocks, except the serial-
interface and internal registers, allowing the registers to
be loaded and values maintained, as long as V
applied. Set SHDN and RXTX logic-low to place the
device in shutdown mode.
After supply voltage ramp up, supply current in shut-
down mode could be high. Program the default value to
SPI register 0 to eliminate high shutdown current.
The standby mode is used to enable the frequency
synthesizer block while the rest of the device is pow-
ered down. In this mode, the PLL, VCO, and LO gener-
ators are on, so that Tx or Rx modes can be quickly
enabled from this mode. Set SHDN to a logic-low and
RXTX to a logic-high to place the device in standby
mode.
The complete receive signal path is enabled in this
mode. Set SHDN to logic-high and RXTX to logic-low to
place the device in Rx mode.
The complete transmitter signal path is enabled in this
mode. Set SHDN and RXTX to logic-high to place the
device in Tx mode.
The MAX2831/MAX2832 feature Rx/Tx calibration modes
to detect I/Q imbalances and transmit LO leakage. In the
Tx calibration mode, all Tx circuit blocks, except the PA
driver and external PA, are powered on and active. The
AM detector and receiver I and Q channel buffers are
also on, along with multiplexers in the receiver side to
route this AM detector’s signal. In this mode, the LO
leakage calibration is done only for the LO leakage sig-
nal that is present at the center frequency of the channel
(i.e., in the middle of the OFDM or QPSK spectrum). The
LO leakage calibration includes the effect of all DC off-
sets in the entire baseband paths of the I/Q modulator
and direct leakage of the LO to the I/Q modulator output.
32
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Modes of Operation
Tx/Rx Calibration Mode
Transmit (Tx) Mode
Receive (Rx) Mode
Shutdown Mode
Standby Mode
CC
is
The LO leakage and sideband detector output are
taken at the receiver I and Q channel outputs during
this calibration phase.
During Tx LO leakage and I/Q imbalance calibration, a
sine and cosine signal (f = f
band I/Q Tx pins from the baseband IC. At the LO leak-
age and sideband-detector output, the LO leakage
corresponds to the signal at f
suppression corresponds to the signal at 2 x f
output power of these signals vary 1dB for 1dB of varia-
tion in the LO leakage and sideband suppression. To
calibrate the Tx path, first set the power-detector gain
to 9dB using D12:D11 in Register 5 (see Table 21).
Adjust the DC offset of the baseband inputs to minimize
the signal at f
band input relative magnitude and phase offsets to
reduce the signal at 2 x f
In Rx calibration mode, the calibrated Tx RF signal is
internally routed to the Rx inputs. In this mode, the
VCO/LO generator/PLL blocks are powered on and
active except for the low-noise amplifier (LNA).
The MAX2831 EV kit can be used as a starting point for
layout. For best performance, take into consideration
grounding and RF, baseband, and power-supply rout-
ing. Make connections from vias to the ground plane as
short as possible. Do not connect the device ground
pin to the exposed paddle ground. Keep the buffered
clock
possible. Do not share the trace with the RF input layer,
especially on or inter-layer or back side of the board.
On the high-impedance ports, keep traces short to min-
imize shunt capacitance. EV kit Gerber files can be
requested at www.maxim-ic.com.
To minimize coupling between different sections of the
IC, a star power-supply routing configuration with a
large decoupling capacitor at a central V
ommended. The V
each going to a separate V
a bypass capacitor as close as possible to each supply
pin. This arrangement provides local decoupling at
each V
for a low-inductance ground connection. Do not share
the capacitor ground vias with any other branch and the
exposed paddle ground.
CC
pin. Use at least one via per bypass capacitor
output
TONE
Applications Information
CC
(LO leakage). Then, adjust the base-
traces branch out from this node,
trace
TONE
CC
Power-Supply Layout
TONE
.
node in the circuit. Place
TONE
) is input to the base-
as
and the sideband
Layout Issues
CC
short
node is rec-
TONE
. The
as