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MAX2602 Evaluation Kit
_______________General Description
The MAX2602 evaluation kit (EV kit) simplifies the evaluation of the MAX2602 1W RF power transistor for 900MHz band applications. The EV kit demonstrates the MAX2602 in a 3.6V, 836MHz, 1W (30dBm) RF power amplifier for constant-envelope applications. The EV kit is shipped with a MAX2602, which contains an internal biasing diode. With a simple modification, the MAX2602 EV kit can be used to emulate the MAX2601, which does not have an internal biasing diode.
____________________________Features
o 1W (30dBm) Output Power at 836MHz o 50 Inputs and Outputs o +2.7V to +5.5V Supply Range o 11dB Gain at 836MHz
Evaluates: MAX2601/MAX2602
______________Ordering Information
PART MAX2602EVKIT-SO TEMP. RANGE -40C to +85C BOARD TYPE Surface Mount
____________________Component List
DESIGNATION QTY C1, C2 C3 C4 C5-C8, C11, C12 C9, C11 L1 L2 R1 R2 R3 IN, OUT U1 None None 2 1 1 6 2 1 1 1 1 1 2 1 1 1 DESCRIPTION 2pF surface-mount capacitors 10pF surface-mount capacitor 12pF surface-mount capacitor 1000pF surface-mount capacitors 0.1F surface-mount capacitors 100nH surface-mount inductor 18.5nH surface-mount spring inductor Coilcraft A05T (Note 1) 430 surface-mount resistor 24 surface-mount resistor 0 resistor Edge-mount SMA connectors MAX2602ESA (8-pin, thermally enhanced SO) MAX2601/MAX2602 data sheet Printed circuit board
_________________________Quick Start
The following section provides instructions for setting up the MAX2602 EV kit as a 1W RF power amplifier.
Test Equipment Required
* * * * RF signal generator capable of at least 20dBm of output power at 836MHz Attenuator that can handle at least 30dBm (1W) of RF power (used to protect the test equipment) RF spectrum analyzer for use at 836MHz (alternatively, a power meter can be used) DC power supply capable of delivering 1A at +2.7V to +5.5V
Connections and Setup
Follow these steps for connecting the EV kit: 1) Connect a 50 RF signal generator capable of supplying at least 20dBm at 836MHz to the RF input SMA connector ("IN"). Set the generator's initial output to a much lower power (-10dBm, for instance). Keep this generator's RF output off at this time. 2) Connect a fixed attenuator that can handle 1W of power to the output SMA connector ("OUT"). This attenuator reduces the power to the test equipment and protects it from overload. Connect this attenuator's output to a spectrum analyzer that is set to display 836MHz. It may be possible to set a referencelevel offset on the analyzer to compensate for the attenuator. Consult your spectrum analyzer's manual for details. 3) Set the power supply to +3.6V with a 1A current limit. Disable the output. Connect the power supply to the VC terminal on the EV kit through an ammeter.
Note 1: Contact Coilcraft by phone at (800) 322-2645, by fax at (847) 639-1469, or on the World Wide Web at http://www.coilcraft.com.
________________________________________________________________ Maxim Integrated Products
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MAX2602 Evaluation Kit Evaluates: MAX2601/MAX2602
4) Connect the same power supply through a separate lead to the EV kit's VB terminal. 5) Verify that all the connections are correct to avoid damaging the transistor or your test equipment. 6) Turn on the 3.6V supply. Note the supply current with the RF generator off. It should be around 100mA. 7) Activate the RF signal generator and slowly increase the generator's output power to 20dBm. At this time, the supply current should be about 500mA, and the output power should be 30dBm. emitter inductance as low as possible, as excessive emitter inductance can degrade the performance of any RF common-emitter amplifier. The bottom-side contact is also the principal path for heat dissipation, and must be connected to a large ground plane.
Biasing
Capacitors C5, C9, and C11 provide decoupling for the bias supply. The transistor's bias current is set by the internal biasing diode's current. This current is set by the following equation: IB = VB - 0.75V R1
_______________Detailed Description
Figure 1 is the schematic for the MAX2602 EV kit as shipped. The circuit consists of four blocks: power-supply decoupling, a bias network, and both input and output matching networks. The amplifier built on this board is biased for class AB operation at 1W of output power, and provides high efficiency.
The collector current is scaled to the bias current: IC = 15IB. R3 is used as a jumper. The transistor's base is biased through R2 and L1 (a choke). For more information on the internal biasing diode's operation, refer to the MAX2601/MAX2602 data sheet.
Supply Decoupling Circuitry and Grounding
Capacitors C8 and C10 provide decoupling for VC. The collector has two separate pins: one for the VC input (connected through choke L2), and one for the RF output. The most important contact for the MAX2602 is not on the top of the board; it is the bottom-side emitter contact that is connected to ground. This contact keeps
Input Matching Network
The transistor's RF input does not present a 50 impedance, so a matching network is required for proper operation in a 50 environment. This network consists of capacitor C1 to ground, approximately 1 inch (or 2.5cm) of the 50 transmission line (T1), a DCblocking capacitor (C6), and a shunt capacitor at the transistor base (C4).
VB C9 0.1F C5 1000pF
R1 430
C11 1000pF
R3 0
C12 1000pF C8 1000pF C7 1000pF C10 0.1F
VC
L1 100nH C6 1000pF
R2 24
L2 18.5nH 3 1 4 8
OUT C3 10pF T2 C2 2pF
IN C1 2pF T1 C4 12pF
U1
5 2, 6, 7 BACK-SIDE SLUG
Figure 1. MAX2602 EV Kit Schematic
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MAX2602 Evaluation Kit Evaluates: MAX2601/MAX2602
VB C9 0.1F C5 1000pF
R1 0
C11 1000pF
C12 1000pF C8 1000pF C7 1000pF C10 0.1F
VC
L1 100nH C6 1000pF
L2 18.5nH R2 24 4 5 3 1 8
OUT C3 10pF T2 C2 2pF
IN C1 2pF T1 C4 12pF
U1
2, 6, 7 BACK-SIDE SLUG
Figure 2. MAX2602 EV Kit Schematic Without the Bias Diode
Output Matching Network
The RF output is taken from pin 8 and is not at 50 impedance, so a matching network is required. The matching network consists of a shunt capacitor at the collector (C3), a DC-blocking capacitor (C7), a 50 transmission line (T2), and a shunt capacitor (C2).
this mode, be sure to turn the VC supply on before the VB supply. When turning the part off, turn the VB supply off first and then the VC supply. External bias voltages ranging from 0V to 0.85V are typically used.
_____________Layout Considerations
For best results, use the MAX2602 EV kit as a layout guide. The most critical connection is the emitterground contact on the MAX2602's bottom side. On the EV kit, this contact is made through a large (0.1 inch, 2.5mm diameter) plated through-hole in the board, located directly under the part. This contact must be soldered directly to a large ground plane, as it is the principal path for heat dissipation, as well as the lowinductance emitter ground. The MAX2602 EV kit uses its ground plane as the heatsink.
Evaluating the MAX2602 Without the Biasing Diode
To evaluate the MAX2602 without the biasing diode (functionally equivalent to the MAX2601), the 0 resistor (R3) must be removed, and the 430 resistor (R1) must be replaced by a 0 resistor (a short) (Figure 2). Now an external bias voltage may be connected to the EV kit's VB input. The biasing diode is no longer connected, so the EV kit will not work without an external biasing voltage. To avoid damage to the MAX2602 in
_______________________________________________________________________________________
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MAX2602 Evaluation Kit Evaluates: MAX2601/MAX2602
1.0"
Figure 3. MAX2602 EV Kit Component Placement Guide
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Figure 4. MAX2602 EV Kit PC Board Layout--Component Side
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Figure 5. MAX2602 EV Kit PC Board Layout--Solder Side (ground plane and heatsink)
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.
4 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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