MAX2233EVKIT Maxim Integrated Products, MAX2233EVKIT Datasheet - Page 6

• Manufacturer Part Number: MAX2233EVKIT
• Description: RF Modules & Development Tools MAX2233 EVAL KIT MAX2233 EVAL KIT
• Manufacturer: Maxim Integrated Products

Specifications of MAX2233EVKIT

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

900MHz ISM-Band, 250mW Power Amplifiers
with Analog or Digital Gain Control
The MAX2232/MAX2233 are nonlinear power amplifiers
(PAs) intended for constant envelope applications (FM,
FSK, GMSK). The devices operate over the 902MHz to
928MHz frequency range and provide typically 250mW
of output power and 44% efficiency from a single +2.7V
to +5.5V supply. Both devices typically provide 24dB of
gain, which is adjustable over a continuous 24dB range
through an analog voltage on CTRL of the MAX2232 or
in two 10dB steps through the 2-bit programmable gain
inputs (D0, D1) on the MAX2233. A low-power shutdown
mode on both devices reduces supply current to 0.2µA.
All bias, gain control, and temperature-sensing circuitry
is provided on-chip to save board space and reduce
component count. The signal path includes a variable
gain amplifier (VGA), an output driver, and an output
power transistor. On-chip interstage matching networks
are provided for optimal loading and power transfer.
Internal bias circuitry responds to CTRL and SHDN of
the MAX2232, or to the 2-bit gain/shutdown control
DAC of the MAX2233, providing optimum biasing and
efficiency as well as shutdown and ramp control func-
tions. A unique temperature-sensing circuit protects the
device from overheating by shutting down the PA until
a safe temperature is resumed.
The devices come in a 16-pin PQSOP package, which
incorporates a slug on the bottom of the device to
increase heat conduction and provide a low induc-
tance path to ground.
The input stage includes a variable gain amplifier
(VGA) with 24dB gain-control range. With the appropri-
ate matching network, the input VSWR is nominally
1.5:1 during operation and the change in VSWR is only
1.2:1, relative to normal operation. This stage remains
active during standby mode (MAX2232) to provide a
constant input impedance but is off during shutdown
mode (MAX2232/MAX2233). AC-couple this port with a
DC-blocking capacitor.
The driver provides gain to overcome interstage match-
ing losses and to produce a signal large enough to
drive the output power transistor into saturation. The
driver stage is off during standby (MAX2232) and shut-
down (MAX2232/MAX2233) modes.
The output power transistor delivers +24dBm of output
power from a single +3.6V supply. The transistor’s
open-collector output requires a pull-up inductor to
6
RF Input Stage (Variable Gain Amplifier)
_______________________________________________________________________________________
Detailed Description
(Output Power Transistor)
RF Second Stage (Driver)
RF Output Stage
V
matching network to ensure optimum output power.
Connect the output matching network to RFOUT (pin
8). See the Typical Application Circuit for bias and
matching components suitable for 900MHz operation.
The ground of the output stage is connected to a metal
slug on the bottom of the MAX2232/MAX2233’s 16-pin
PQSOP package. The metal slug increases heat con-
duction and provides a low-inductance path to ground.
Solder the metal slug to the PC-board ground plane.
Drive the shutdown (SHDN) pin below 0.6V to place the
MAX2232 in shutdown mode. The VGA, driver, and out-
put transistor are off in shutdown mode and the supply
current is typically reduced to 0.2µA. When SHDN is
above 2.0V, the device is enabled.
Drive SHDN above 2.0V and CTRL below 0.4V to place
the MAX2232 in standby mode. In standby mode, the
VGA remains biased while the driver and output tran-
sistor are disabled. Supply current is typically 20mA in
standby mode. This mode allows the device to maintain
a good input VSWR while maintaining 38dB of isolation.
This is useful to users who drive the PA with a direct
modulated VCO, where pulling of the VCO results from
changes in the input VSWR.
The voltage applied to the gain-control (CTRL) pin varies
the output power of the MAX2232 continuously over a
24dB range. An internal comparator holds the PA to a
constant peak output power if V
V
sents a high input impedance, allowing the V
to be set with a resistor-divider or a voltage output DAC.
The internal bias circuitry of the MAX2232 automatically
ramps the output power of the PA down or up at a con-
stant rate (in W/sec) when switched in or out of shut-
down mode. The output power is ramped to the level set
by V
fall time ramp is set by placing a capacitor, C
between RAMP+ and RAMP-. This provides an easy
means of avoiding spectral splatter and complying with
transmit mask requirements, without using a separate
controller. The output power rise and fall time is set by
the value of C
___________________________MAX2232
CTRL
CC
CTRL
for proper biasing, as well as a proper output
below 0.4V, the PA is in standby mode. CTRL pre-
on the MAX2232. The output power rise and
RAMP
.
Output Power Autoramping
and Power Management
Analog Gain Control
CTRL
Analog Gain Control
is above 2.2V. For
Shutdown Mode
Standby Mode
CTRL
voltage
RAMP
,