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MAX2402 Evaluation Kit
General Description
The MAX2402 evaluation kit (EV kit) simplifies evaluation of the MAX2402 transmitter. The EV kit enables the testing of all MAX2402 functions with no additional support circuitry and with minimal equipment. Low-Cost, Flexible Transmitter More than 100mW of Output Power Operates from 800MHz to 1000MHz Single +5V Supply Easy Testing of All MAX2402 Features
Features
Evaluates: MAX2402
Component List
DESIGNATION QTY C1 C2 C3, C4, C5 C6 C7, C9, C12 C8 C10 L1 L2 LO+, LOMOD, OUT R1 R2, R5 R3, R4 R6, R7 R8 U1 W1-W4 None 1 1 3 1 2 1 1 1 1 4 1 2 2 2 1 1 4 4 DESCRIPTION 10F, 25V, 10%, tantalum capacitor 0.1F, 50V, 10% ceramic capacitor 39pF, 50V, 5% ceramic capacitors 150pF, 50V, 5% ceramic capacitor 0.01F, 50V, 10% ceramic capacitors 100pF, 50V, 5% ceramic capacitor 220pF 27nH, 20% inductor Coilcraft 0805CS-270XMBC 47nH, 20% inductor Coilcraft 0805CS-470XMBC Female SMA connectors 121, 1% resistor 100, 5% resistors 49.9, 1% resistors 51, 5% resistors 1k, multi-turn potentiometer MAX2402EAP 2-pin headers 2-pin shunts PART MAX2402EVKIT-SO
Ordering Information
TEMP. RANGE -40C to +85C BOARD TYPE Surface Mount
EV Kit
________________________________________________________________ Maxim Integrated Products
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For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX2402 Evaluation Kit Evaluates: MAX2402
_________________________Quick Start
The MAX2402 EV kit is fully assembled and factory tested. Do not turn on the power until all connections are made.
Analysis
1) R1 is a 121 surface-mount resistor on the EV kit which is parallel with the 50 termination of the spectrum analyzer. This sets the load of the power amplifier at 35, 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 accurate information. R1 can be removed, if 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 poweramplifier output to the LO port and cable. When signal 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 necessary to adjust BADJ to higher than 2.5V 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 voltage. The VGC range is 0V to VCC. The output power should be at a minimum when VGC is adjusted below 0.8V. The output power should be at a maximum when VGC is adjusted above (VCC - 0.5V). 4) The BADJ pin is used to control the bias level of the final stages of the PA. The adjustment range on BADJ is 0V to VCC, with 0V representing the greatest 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 VCC 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 VCC/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.
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) The LO port can be driven single-ended or differentially. For single-ended drive, connect an SMA cable from the 1000MHz signal source to the LO+ SMA input on the EV kit. For differential drive, install a 220pF ceramic capacitor (not provided) at site C11. Using SMA cables, connect the signal source to the LO+ and LO- inputs through a balun with sufficient bandwidth. The EV kit was designed for single-ended or differential LO drive. In your final layout, capacitors C10 and C11 are not required. For single-ended LO drive applications, ground the unused LO port as close to the package as possible. For differential drive applications, connect LO lines directly to LO port pins. Coupling capacitors are not required, as the LO ports are internally AC coupled. 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 VCC and GND terminals on the EV kit. 5) Place a shorting termination on the MOD SMA connector 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.
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MAX2402 Evaluation Kit
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 VCC jumper (W1) on the EV kit will connect BADJ to GND, while removing the GND jumper (W2) will connect BADJ to VCC. Removing both will cause BADJ to rely on its internal bias. 5) The MAX2402 SHDN pin connects to VCC through a jumper and 100. 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 1A. 6) The modulated spectrum can be examined on the spectrum analyzer by removing the shorting termination and supplying a modulation signal to the SMA MOD input. The MOD input is linear from approximately 1.5V to 3.5V, and has a bandwidth of DC to 25MHz. The MOD input is self-biasing to approximately VCC/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 carrier rejection. The MOD input will act as an attenuator if it is left open.
SHDN The SHDN jumper (W4) shorts the SHDN input to VCC 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 VCC when in place.
BADJ The two bias adjust jumpers connect either end of the 1k potentiometer to VCC and GND through 50 resistors. The wiper on the potentiometer has been factory adjusted to provide 2.5V 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 VCC 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 board layout. C3, C4, and C5 should be small surface-mount capacitors, placed directly from each VCC pin to the adjacent ground. Place them as close to the MAX2402 as possible, and make connections 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 VCC 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 lowvalue capacitor, since the high-impedance at the BADJ node may be sensitive to circuit noise. Although the evaluation board uses four layers, it is possible to use two.
Adjustments and Control
VGC The VGC jumper (W3) shorts the VGC input of the MAX2402 to VCC. 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 VCC when in place.
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MAX2402 Evaluation Kit Evaluates: MAX2402
VCC
W4 R2 100 R6 51 W1 SHDN R8 1k BADJ W2 R7 51 LO+ MOD
W3 R5 100 VGC
C5 39pF 4 VCC 1 VGC SHDN BADJ
C4 39pF 12 VCC
C3 39pF 19 VCC OUT OUT LGND
C7 0.01F
C2 0.1F C8 100pF
C1 10F 25V C9 0.01F OUT
16 14 11
L2 47nH
C12 0.01F
9 10
C6 150pF L1 27nH
R1 121
U1
2 C10 220pF R4 49.9 LOC11 OPEN R3 49.9 7 LOMOD
GND GND GND
3 5 8 13 15 17 18 20 GND
MAX2402
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LO+
GND GND GND GND GND
Figure 1. MAX2402 EV Kit Schematic
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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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MAX2402 Evaluation Kit Evaluates: MAX2402
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
6 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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