MAX2361EGM-D Maxim Integrated Products, MAX2361EGM-D Datasheet - Page 12

• Manufacturer Part Number: MAX2361EGM-D
• Description: RF Transmitter Complete Dual-Band Q uadrature Transmitte
• Manufacturer: Maxim Integrated Products

Specifications of MAX2361EGM-D

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

The MAX2361 complete quadrature transmitter accepts
differential I/Q baseband inputs with external common-
mode bias. A modulator upconverts this to IF frequency
in the 120MHz to 380MHz range. A gain-control voltage
pin (GC) controls the gain of both the IF and RF VGAs
simultaneously to achieve the best current consumption
and linearity performance. The IF signal is brought off-
chip for filtering, then fed to a single sideband upcon-
verter followed by the RF VGA and PA driver. The RF
upconverter requires an external VCO for operation.
The IF PLL, RF PLL, and operating mode can be pro-
grammed by an SPI/QSPI/MICROWIRE-compatible 3-
wire interface.
The following sections describe each block in the
MAX2361 Functional Diagram.
Differential in-phase (I) and quadrature-phase (Q) input
pins are designed to be DC-coupled and biased with the
baseband output from a digital-to-analog converter
(DAC). I and Q inputs need a DC bias of V
current-drive capability of 8µA. The I and Q inputs
capacitance is typically 0.3pF differential. Common-
mode voltage works within a 1.35V to (V
range. The IF VCO output is fed into a divide-by-
two/quadrature generator block to derive quadrature LO
components to drive the IQ modulator. The output of the
modulator is fed into the VGA.
There are two VCOs to support high IF and low IF fre-
quencies. The VCOs oscillate at twice the desired IF fre-
quency. Oscillation frequency is determined by external
tank components (see Applications Information). Typical
phase-noise performance for the tank is as shown in the
Typical Operating Characteristics. The high-band and
low-band VCOs can be selected independently of the IF
port being used.
IFLO provides a buffered LO output when BUF_EN is 1.
The IFLO output frequency is equal to the VCO fre-
quency when BUF_DIV is 0, and half the VCO frequen-
cy when BUF_DIV is 1. The output power is -12dBm.
This output is intended for applications where the
receive IF is the same frequency as the transmit IF.
Complete Dual-Band
Quadrature Transmitters
12
______________________________________________________________________________________
Detailed Description
IFLO Output Buffer
I/Q Modulator
CC
CC
IF VCOs
/2 and a
- 1.25V)
The IF/RF PLL uses a charge-pump output to drive a
loop filter. The loop filter typically is passive second-
order lead lag filter. Outside the filter’s bandwidth,
phase noise is determined by the tank components.
The two components that contribute most significantly
to phase noise are the inductor and varactor. Use high-
Q inductors and varactors to maximize equivalent par-
allel
RCP_TURBO1, and RCP_TURBO2 bits can be set to
enable turbo mode. Turbo mode provides maximum
charge-pump current during frequency acquisition.
Turbo mode is disabled after frequency acquisition is
achieved. When turbo mode is disabled, charge-pump
current returns to the programmed levels as set by ICP
and RCP bits in the CONFIG register (Table 3).
The PSS bit selects the RFPLL prescaler speed inde-
pendent of the MODE bits. This enables PCS band
VCO locking when transmitting in the cellular band. For
VCO frequency above 1300MHz, set PSS to 1.
The IF VGA allows varying an IF output level that is con-
trolled by GC voltage. The voltage range on GC of 0.6V
to 2.4V provides a gain-control range of 85dB. There
are two differential IF output ports from the VGA.
IFOUTL+/IFOUTL- are optimized for low IF operation
(120MHz to 235MHz); IFOUTH+/IFOUTH- support high
IF operation (120MHz to 380MHz). IFOUTL supports
FM mode by providing higher IF output level when
MODE is set to 00.
The RF transmit mixer uses a single sideband architec-
ture to eliminate an off-chip RF filter. The single sideband
mixer has IF input stages that correspond to IF output
ports of the VGA. The mixer is followed by the RF VGA.
The RF VGA is controlled by the same GC pin as the IF
VGA to provide optimum current consumption and linear-
ity performance. The total power-control range is
>100dB.
The MAX2361 includes three power-amplifier (PA) dri-
vers. Each is optimized for the desired operating fre-
quency. RFL is optimized for cellular-band operation.
RFH0 and RFH1 are optimized for split-band PCS opera-
tion. Use RFH0 in single high-band output such as
TDMA or W-CDMA. The PA drivers have open-collector
outputs and require pullup inductors. The pullup induc-
tors can act as the shunt element in a shunt series
match.
resistance.
The
Single Sideband Mixer
IF_TURBO_CHARGE,
IF/RF PLL
PA Driver
IF VGA