MAX2602 - Maxim Integrated Products, Inc.

_________________________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 (alterna-

tively, 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 50ΩRF signal generator capable of sup-

plying at least 20dBm at 836MHz to the RF input

SMA connector (“IN”). Set the generator’s initial out-

put 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 attenua-

tor’s output to a spectrum analyzer that is set to dis-

play 836MHz. It may be possible to set a reference-

level offset on the analyzer to compensate for the

attenuator. Consult your spectrum analyzer’s manu-

al for details.

3) Set the power supply to +3.6V with a 1A current

limit. Disable the output. Connect the power supply

to the VCterminal on the EV kit through an ammeter.

_______________General Description

The MAX2602 evaluation kit (EV kit) simplifies the evalu-

ation 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

♦1W (30dBm) Output Power at 836MHz

♦50ΩInputs and Outputs

♦+2.7V to +5.5V Supply Range

♦11dB Gain at 836MHz

Evaluates: MAX2601/MAX2602

MAX2602 Evaluation Kit

________________________________________________________________

Maxim Integrated Products

PART TEMP. RANGE BOARD TYPE

MAX2602EVKIT-SO -40°C to +85°C Surface Mount

QTY DESCRIPTION

C1, C2 2

C3 1

C4 1 12pF surface-mount capacitor

C5–C8,

C11, C12 6

C9, C11 2 0.1µF surface-mount capacitors

L1 1

L2 1

R1 1

R2 1 24Ωsurface-mount resistor

R3 1 0Ωresistor

IN, OUT 2 Edge-mount SMA connectors

U1 1 MAX2602ESA (8-pin, thermally

enhanced SO)

1000pF surface-mount capacitors

10pF surface-mount capacitor

2pF surface-mount capacitors

DESIGNATION

100nH surface-mount inductor

18.5nH surface-mount spring inductor

Coilcraft A05T (Note 1)

430Ωsurface-mount resistor

____________________Component List

______________Ordering Information

None 1 MAX2601/MAX2602 data sheet

None 1 Printed circuit board

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.

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 408-737-7600 ext. 3468.

Evaluates: MAX2601/MAX2602

MAX2602 Evaluation Kit

2 _______________________________________________________________________________________

4) Connect the same power supply through a separate

lead to the EV kit’s VBterminal.

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.

_______________Detailed Description

Figure 1 is the schematic for the MAX2602 EV kit as

shipped. The circuit consists of four blocks: power-sup-

ply decoupling, a bias network, and both input and out-

put matching networks. The amplifier built on this board

is biased for class AB operation at 1W of output power,

and provides high efficiency.

Supply Decoupling Circuitry

and Grounding

Capacitors C8 and C10 provide decoupling for VC. The

collector has two separate pins: one for the V Cinput (con-

nected 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 con-

tact that is connected to ground. This contact keeps

emitter inductance as low as possible, as excessive

emitter inductance can degrade the performance of

any RF common-emitter amplifier. The bottom-side con-

tact 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:

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 infor-

mation on the internal biasing diode’s operation, refer to

the MAX2601/MAX2602 data sheet.

Input Matching Network

The transistor’s RF input does not present a 50Ω

impedance, so a matching network is required for prop-

er operation in a 50Ωenvironment. This network con-

sists of capacitor C1 to ground, approximately 1 inch

(or 2.5cm) of the 50Ωtransmission line (T1), a DC-

blocking capacitor (C6), and a shunt capacitor at the

transistor base (C4).

I = V - 0.75V

430ΩR3

0Ω

18.5nH

0.1µF

2pF

1000pF

C10

0.1µF

1000pF

C11

1000pF C12

1000pF

100nH

24Ω

12pF

2, 6, 7

BACK-SIDE SLUG

2pF

OUT

10pF

Figure 1. MAX2602 EV Kit Schematic

Output Matching Network

The RF output is taken from pin 8 and is not at 50Ω

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 50Ω

transmission line (T2), and a shunt capacitor (C2).

Evaluating the MAX2602

Without the Biasing Diode

To evaluate the MAX2602 without the biasing diode

(functionally equivalent to the MAX2601), the 0Ωresis-

tor (R3) must be removed, and the 430Ωresistor (R1)

must be replaced by a 0Ωresistor (a short) (Figure 2).

Now an external bias voltage may be connected to the

EV kit’s VBinput. The biasing diode is no longer con-

nected, so the EV kit will not work without an external

biasing voltage. To avoid damage to the MAX2602 in

this mode, be sure to turn the VCsupply on before the

VBsupply. When turning the part off, turn the VBsupply

off first and then the VCsupply. 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 emitter-

ground 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 low-

inductance emitter ground. The MAX2602 EV kit uses

its ground plane as the heatsink.

Evaluates: MAX2601/MAX2602

MAX2602 Evaluation Kit

_______________________________________________________________________________________ 3

0Ω

18.5nH

0.1µF

2pF

1000pF

C10

0.1µF

1000pF

C11

1000pF C12

1000pF

100nH R2

24Ω

12pF

2, 6, 7

BACK-SIDE SLUG

2pF

OUT

10pF

Figure 2. MAX2602 EV Kit Schematic Without the Bias Diode

Evaluates: MAX2601/MAX2602

MAX2602 Evaluation Kit

Figure 3. MAX2602 EV Kit Component Placement Guide

1.0"

Figure 4. MAX2602 EV Kit PC Board Layout—Component Side

1.0"

Figure 5. MAX2602 EV Kit PC Board Layout—Solder Side (ground

plane and heatsink)

1.0"

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.

_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600