MAX2121 Evaluation Kit
Evaluates: MAX2121
3
Maxim Integrated
Procedure
The EV kit is fully assembled and factory tested. Follow
the instructions in the
Connections and Setup
section for
proper device evaluation.
Measurement Considerations
The EV kit includes on-board matching circuitry at the
MAX2121 RF input to convert the 50
I
source to a 75
I
input. Note that the input power to the device must
be adjusted to account for the -6dB power loss of the
matching resistor network.
Connections and Setup
This section provides a step-by-step guide to testing the
basic functionality of the EV kit in UHF mode.
Caution:
Do not turn on DC power or RF signal generators until
all connections are completed.
1) Verify that all jumpers are in place.
2) With its output disabled, connect the DC power supply
to VGC set to 0.5V (maximum gain).
3) With its output disabled, set the DC power supply to
3.3V. Connect the power supply to the VCC (through
an ammeter if desired) and GND terminals on the EV
kit. If available, set the current limit to 200mA.
4) With its output disabled, set the RF signal generator
to a 955MHz frequency at -69dBm to account for
the 6dB resistive pad loss. When measuring noise
figure, this 6dB must also be accounted for by
subtracting 6dB from the measured noise figure,
unless the pad has been removed.
5) Connect the output of the RF signal generator to the
SMA connector labeled RF _INPUT on the evaluation
board.
6) Connect the PC to the INTF3000 Interface Board
using a USB A male to USB B male cable. On
INTF3000, place a jumper between pins 1-2 of JU1
(VBUS Pos). Connect a 25-pin connector of the
INTF3000 (J4) directly to the 25-pin connector of the
EV kit (J6).
7) Turn on the 3.3V V
CC
power supply, followed by the
3V gain-control power supply. The supply current
from the 3.3V V
CC
supply should read approximately
150mA, and the supply current from the 3V V
GC
should read approximately 50
F
A. Be sure to adjust
the power supply to account for any voltage drop
across the ammeter.
8) Install and run the IC control software. Software is
available for download at
9) Load the default register settings from the control
software by clicking
Edit: Load Defaults
.
10) Connect the output to a spectrum analyzer or an
oscilloscope.
11) Enable the RF signal generator’s output.
12) Activate and set the power level of the RF
generator to achieve 1V
P-P
differential across IP/IN or
QP/QN. Note that the intended 200
I
differen-
tial load is dependent on each baseband output
being properly terminated into 50
I
. For example,
terminate IP into a 50
I
spectrum analyzer and
terminate IN into 50
I
. The summation of these two
50
I
terminations and the two series 50
I
resistors
on the EV kit equates to the desired 200
I
differential
load. In this configuration, the 1V
P-P
differential
voltage across IP/IN is reduced to 250mV
P-P
(-8dBm)
at the spectrum-analyzer input.
13) Check the I/Q outputs.
14) Observe the baseband output at 5MHz with differen-
tial 1V
P-P
.
Layout Considerations
The EV kit can serve as a guide for PCB layout. Keep RF
signal lines as short as possible to minimize losses and
radiation. Use controlled impedance on all high-frequen-
cy traces. The exposed pad must be soldered evenly
to the board’s ground plane for proper operation. Use
abundant vias beneath the exposed pad for maximum
heat dissipation. Use abundant ground vias between RF
traces to minimize undesired coupling.
To minimize coupling between different sections of the
IC, the ideal power-supply layout is a star configuration,
which has a large decoupling capacitor at the central
V
CC
node. The V
CC
traces branch out from this node,
with each trace going to separate V
CC
pins of the IC.
Each V
CC
pin must have a bypass capacitor with low
impedance to ground at the frequency of interest. Do
not share ground vias among multiple connections to the
PCB ground plane.
