MAX2366 MAXIM [Maxim Integrated Products], MAX2366 Datasheet - Page 11

• Manufacturer Part Number: MAX2366
• Description: Complete Dual-Band Quadrature Transmitters
• Manufacturer: MAXIM [Maxim Integrated Products]

The MAX2366 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 300MHz range. A gain control voltage
pin (VGC) controls the gain of both the IF and RF VGAs
simultaneously to achieve best noise and linearity per-
formance. The IF signal is brought off-chip for filtering,
then fed to a single sideband upconverter 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 programmed by an SPI/QSPI/
MICROWIRE-compatible 3-wire interface.
The following sections describe each block in the
MAX2366 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 6µA. Common-mode voltage
will work within a 1.35V to (V
I and Q will be driven differentially with a 200mV
baseband signal. Optionally, I and Q may be pro-
grammed for 100mV
in the configuration register. The IF VCO output is fed
into a divide-by-two/quadrature generator block to derive
quadrature 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 appli-
cations. 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 Table 1. The high-band and low-band VCOs
can be selected independently of the IF port being
used.
Table 1. Typical VCO Phase Noise
(IF = 130.38MHz)
OFFSET (kHz)
12.5
120
900
30
1
______________________________________________________________________________________
RMS
Detailed Description
operation with the IQ_LEVEL bit
CC
- 1.25V) range. Typically,
PHASE NOISE (dBc)
I/Q Modulator
-105
-111
-121
-128
-80
CC
IF VCOs
/2 and a
RMS
Quadrature Transmitters
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 -6dBm. This
output is intended for applications where the receiver IF
is the same frequency as the transmit IF.
The IF/RF PLL uses a charge-pump output to drive a
loop filter. The loop filter will typically be a passive sec-
ond-order lead lag filter. Outside the filter’s bandwidth,
phase noise will be determined by the tank compo-
nents. The two components that contribute most signifi-
cantly to phase noise are the inductor and varactor.
Use high-Q inductors and varactors to maximize equiv-
alent parallel resistance. The IF_TURBO_CHARGE and
the RF_TURBO_CHARGE bits in the CONFIG register
can be set to 1 to enable turbo mode. Turbo mode pro-
vides maximum charge-pump current during frequency
acquisition. Turbo mode is disabled after the second
transition from phase lead to phase lag or from phase
lag to phase lead. Turbo mode is also disabled after
frequency acquisition is achieved. When turbo mode is
disabled, charge-pump current will return to the pro-
grammed levels as set by ICP and RCP bits in the
CONFIG register (Table 4).
The IF VGA allows varying an IF output level that is con-
trolled by the VGs. The voltage range on VGC of +0.5V
to +2.6V 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) for IFOUTH+/IFOUTH- support
high IF operation (120MHz to 300MHz). IFOUTL ports
support direct VCO FM modulation. The differential IF
output port has an output impedance of 600Ω when
pulled up to V
The RF transmit mixer uses a single sideband architec-
ture to eliminate an off-chip RF filter. The single side-
band 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 VGC pin as
the IF VGA to provide optimum linearity and noise per-
formance. The total power control range is >100dB.
The MAX2366 includes three power-amplifier (PA) dri-
vers. Each is optimized for the desired operating fre-
quency. RFL is optimized for cellular-band operation.
Complete Dual-Band
CC
through a choke.
Single Sideband Mixer
IFLO Output Buffer
IF/RF PLL
PA Driver
IF VGA
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