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MAX2402 Evaluation Kit
_______________General Description
The MAX2402 evaluation kit (EV kit) simplifies the evalu-
ation of the MAX2402 transmitter. The EV kit will enable
the testing of all functions of the MAX2402 with no addi-
tional support circuitry and with minimal equipment.
____________________________Features
o
Low-Cost, Flexible Transmitter
o
More than 100mW of Output Power
o
Operates from 800MHz to 1000MHz
o
Single +5V Supply
o
Easy Testing of All MAX2402 Features
Evaluates: MAX2402
____________________Component List
DESIGNATION QTY
C1
C2
C3, C4, C5
C6
C7, C9
C8
L1
L2
LO+, LO-
MOD, OUT
R1
R2, R5
R3, R4
R6, R7
R8
U1
W1–W4
None
1
1
3
1
2
1
1
1
4
1
2
2
2
1
1
4
4
DESCRIPTION
10µF, 25V, 10%, tantalum capacitor
0.1µF, 50V, 10% ceramic capacitor
39pF, 50V, 5% ceramic capacitors
150pF, 50V, 5% ceramic capacitor
0.01µF, 50V, 10% ceramic capacitors
100pF, 50V, 5% ceramic capacitor
27nH, 20% inductor
CoilCraft 0805CS-270XMBC
47nH, 20% inductor
CoilCraft 0805CS-470XMBC
Female SMA connectors
121Ω, 1% resistor
100Ω, 5% resistors
49.9Ω, 1% resistors
51Ω, 5% resistors
1kΩ, multi-turn potentiometer
MAX2402EAP
2-pin headers
2-pin shunts
PART
MAX2402EVKIT-SO
TEMP. RANGE
-40°C to +85°C
BOARD TYPE
Surface Mount
______________Ordering Information
______________________________EV Kit
________________________________________________________________
Maxim Integrated Products
1
Call toll free 1-800-998-8800 for free samples or literature.
MAX2402 Evaluation Kit
Evaluates: MAX2402
_________________________Quick Start
The MAX2402 EV kit is fully assembled and factory test-
ed.
Do not turn on the power until all connections
are made.
The 121Ω can be removed if so desired with about a
0.7dB reduction in transmitted power due to the load
mismatch. The output power (with 1.5dB added to
the displayed power) should be at least 20dBm.
(Note: Before signal is applied to the LO port there
may be a parasitic oscillation on the EV board. This
is caused by parasitic feedback from the power-
amplifier output to the LO port and cable. When sig-
nal is applied to the LO port, this oscillation will
abate.)
2) The output power can be observed for the 800MHz
to 1000MHz LO input range and over the prescribed
input power levels. (Near 800MHz, it may be neces-
sary to adjust BADJ to higher than 2V to maintain
stability.)
3) To observe the effects of the VGC voltage on output
power, connect an adjustable supply to the VGC test
point on the EV kit and remove the VGC jumper (W3).
This supply can now be adjusted and the output
power can be observed as a function of VGC volt-
age. The VGC range is 0V to V
CC
. The output power
should be at a minimum when the VGC is adjusted
below 0.8V. The output power should be at a maxi-
mum when the VGC is adjusted above (V
CC
- 0.5V).
4) The BADJ pin is used to control the bias level of the
final stages of the PA. The adjustment range on the
BADJ is 0V to V
CC
, with 0V representing the most
bias current and 5V the least. More bias current will
result in more output power, less efficiency, and less
distortion. The intended configuration for this pin is a
single resistor pull-up or pull-down to V
CC
or GND,
respectively. The value of this resistor will determine
the bias voltage at the BADJ pin. See Table 1 in the
MAX2402 data sheet for a guide to resistor use at
the BADJ input.
The MAX2402 BADJ input is self biasing to about
V
CC
/2 and can be left open. At low BADJ voltage
settings and lower frequencies within the 800MHz to
1000MHz range, the power-supply current may
increase unacceptably or the circuit may oscillate.
At these lower frequencies, more than 20dBm of
power can easily be obtained with BADJ set at 3V or
above (see the
BADJ Input
section of the MAX2402
data sheet).
Removing the V
CC
jumper (W1) on the EV kit will
connect BADJ to GND, while removing the GND
jumper (W2) will connect BADJ to V
CC
. Removing
both will cause BADJ to rely on its internal bias.
Test Equipment Required
• Signal Source, sine-wave generator with range up to
1000MHz (example: HP8656B)
• Signal Source, function generator with range up to
10MHz
• Spectrum Analyzer with range up to 4GHz (example:
TEK2755AP)
• Power Supply capable of 5V, 300mA output with
current limit
Connections and Signal Conditions
1) Verify that all shunts are across jumpers W1–W4.
2) Connect an SMA cable from the 1000MHz signal
source to the LO+ SMA input (or LO- SMA input) on
the EV kit. Place a shorting termination on LO-. If dif-
ferential drive is desired, connect the SMA cables
from the signal source to a balun with sufficient
bandwidth, and connect cables from the balun 0°
and 180° ports to the LO+ and LO- inputs.
3) Connect an SMA cable from the spectrum analyzer
to the OUT SMA on the EV kit.
4) Connect the power supply to the appropriate V
CC
and GND terminals on the EV kit.
5) Place a shorting termination on the MOD SMA con-
nector to put the mixer in a fully on position.
6) Set LO power to 0dBm and frequency to 900MHz on
the signal source. Do not apply a signal to the DUT
yet, if you have control of this function.
7) Set the spectrum analyzer’s dynamic range for a top
limit of 30dBm, and set the frequency range for an
appropriate setting to view the output.
8) Set the power supply to 5.0V and set the current limit
to 300mA. Apply power.
Analysis
1) There is a 121Ω surface-mount resistor on the EV kit
which is parallel with the 50Ω termination of the
spectrum analyzer. This sets the load of the power
amplifier at 35Ω, which is a close match to the
power-amplifier’s output impedance. As a result, the
spectrum analyzer will display an output power level
which is 1.5dB below the actual transmitted power.
As long as this resistor is on the EV kit, 1.5dB must
be added to any displayed power levels to get accu-
rate information.
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_______________________________________________________________________________________
MAX2402 Evaluation Kit
5) The MAX2402 SHDN pin connects to V
CC
through a
jumper and 100Ω. To test the shutdown function,
ensure that either W1 or W2 is removed, which will
prevent current draw through R6, R7, and R8. When
the SHDN jumper is removed and the SHDN test
point is grounded, the supply current should drop
below 1µA.
6) The modulated spectrum can be examined on the
spectrum analyzer by removing the shorting termina-
tion and supplying a modulation signal to the SMA
MOD input. The MOD input is linear from approxi-
mately 1.5V to 3.5V, and has a bandwidth of DC to
25MHz. The MOD input is self-biasing to approxi-
mately V
CC
/2. Any offset at the MOD input from a
symmetric signal around the self-bias voltage will act
as an offset and cause less than optimal carrier
rejection. Capacitive coupling into the MOD input
will eliminate this situation and result in optimum car-
rier rejection. The MOD input will act as an attenua-
tor if it is left open.
BADJ
The two bias adjust jumpers connect either end of the
1kΩ potentiometer to V
CC
and GND through 50Ω resis-
tors. The wiper on the potentiometer has been factory
adjusted to provide 2V to the BADJ input on the
MAX2402. The BADJ test point is for monitoring the
BADJ voltage. The BADJ jumpers (W1, W2) connect R8
to V
CC
and GND, respectively. BADJ voltage is altered
by adjusting the R8 potentiometer.
Evaluates: MAX2402
Layout Considerations
The evaluation board can serve as a guide for layout of
your board. The following considerations were taken into
account on the evaluation board. C3, C4, and C5 should
be small surface-mount capacitors, placed directly from
each V
CC
pin to the adjacent ground. Place them as
close to the MAX2402 as possible, and make connec-
tions directly to the pins (not through vias or long traces).
C6, C7, and C8 should also be surface mount. C7
should be next to C3. C8 and C9 should be located at
the V
CC
terminal of choke L2. If the LO is driven single-
ended, ground the unused LO port. If a single resistor is
used to bias BADJ, it may be necessary to AC couple
BADJ to ground with a low-value capacitor, since the
high-impedance at the BADJ node may be sensitive to
circuit noise. Although the evaluation board uses four
layers, it is certainly possible to use two.
Adjustments and Control
VGC
The VGC jumper (W3) shorts the VGC input of the
MAX2402 to V
CC
. The VGC test point can be used to
manipulate the gain control voltage. The VGC jumper
(W3) should be removed before trying to control this
VGC voltage. It connects to V
CC
when in place.
SHDN
The SHDN jumper (W4) shorts the SHDN input to V
CC
to keep the part in normal operating condition. The
SHDN test point can be used with a controlling voltage
to power down the MAX2402. The SHDN jumper (W4)
should be removed when adjusting the voltage on the
test pin. It connects to V
CC
when in place.
_______________________________________________________________________________________
3
MAX2402 Evaluation Kit
Evaluates: MAX2402
V
CC
W4
R2
100Ω
R6
51Ω
W1
SHDN
R8
1k
W2
R7
51Ω
LO+
BADJ
MOD
W3
R5
100Ω
VGC
C5
39pF
4
V
CC
1
9
10
VGC
SHDN
BADJ
C4
39pF
12
V
CC
C3
39pF
19
V
CC
OUT
OUT
LGND
C7
0.01µF
C2
0.1µF
C8
100pF
C1
10µF
25V
C9
0.01µF
OUT
16
14
11
L2
47nH
C6
150pF
L1
27nH
R1
121Ω
U1
2
MOD
GND
GND
GND
3
5
8
13
15
17
18
20
GND
MAX2402
6
R4
49.9Ω
LO+
GND
GND
LO-
R3
49.9Ω
7
LO-
GND
GND
GND
Figure 1. MAX2402 EV Kit Schematic
4
_______________________________________________________________________________________
MAX2402 Evaluation Kit
Evaluates: MAX2402
Figure 2. MAX2402 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX2402 EV Kit PC Board Layout—Component Side
Figure 4. MAX2402 EV Kit PC Board Layout—Solder Side
Note: Ground layers 2 and 3 not shown.
_______________________________________________________________________________________
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