Datasheet

Quasi-Measurement Mode
Enabling the quasi-measurement mode changes the
MAX9930 EV kit function from a PA controller to a log
detector. This mode allows for easy measurement of
RFIN versus the SET voltage and these measurements
can then be used to find the intercept and slope
required for the given application.
Place a shunt on pins 2-3 of JU2 and install a shunt
across JU3 to enable the quasi-measurement mode. This
configuration connects the OUT voltage through an
inverting op amp to the SET pin. The quasi-measurement
mode yields a nominal relationship between RFIN
and SET. See Table 2 for quasi-measurement mode
shunt positions.
Filter Capacitor Selection
When functioning as a PA controller, the MAX9930
requires some capacitance to maintain loop stability.
Global Satellite Mobile (GSM) applications require a
control-loop bandwidth of at least 150kHz. A 2200pF
capacitor (C4) is installed to obtain this control-loop
bandwidth. Refer to the Gain and Phase vs. Frequency
graph in the
Applications Information section of the
MAX9930/MAX9931/MAX9932 IC data sheet for
alternative capacitor values.
Evaluating the MAX9931/MAX9932
The MAX9930 can be replaced with the MAX9931 to
allow an input range of -35dBm to +10dBm into 50Ω, or
with the MAX9932 to allow an input range of -30dBm to
+15dBm into 50Ω. Replace U1 with a MAX9931EUA+
or MAX9932EUA+.
Evaluating the MAX9933
The MAX9930 can be replaced with the MAX9933 to
allow an input range of -45dBm to +0dBm into 50Ω.
Replace U1 with a MAX9933EUA+. Once a MAX9933
IC is installed on U1, remove the shunt on JU3 to dis-
connect the quasi-measurement mode circuitry. Place
the shunt on pins 1-2 of JU2 to connect pin 3 of the
MAX9933 to ground. The voltage on the OUT pad
reflects the power level of the RF input signal.
Layout Considerations
A good PCB layout is an essential part of RF
circuit design. The MAX9930EV kit PCB can serve
as a guide for laying out a board using the
MAX9930–MAX9933. Keep traces carrying RF signals
as short as possible to minimize radiation and insertion
loss due to the PCB. Each V
CC
node on the PCB should
have its own decoupling capacitor. This minimizes sup-
ply coupling from one section of the PCB to another.
Using a star topology for the supply layout, in which
each V
CC
node in the circuit has a separate connection
to the central V
CC
node, can further minimize coupling
between sections of the PCB.
Evaluates: MAX9930–MAX9933
MAX9930 Evaluation Kit
_______________________________________________________________________________________ 3
* Default position.
X = a “don’t care” position.
Table 2. Quasi-Measurement Mode
Selection
SHUNT POSITION
JU2 JU3
QUASI-MEASUREMENT MODE
1-2 X Disabled
2-3* Installed* Enabled
X Not installed Disabled
Not installed X Disabled