Datasheet

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General Description

The MAX2235 low-voltage, silicon RF power amplifier

(PA) is designed for use in the 900MHz frequency band.

It operates directly from a single +2.7V to +5.5V supply,

making it suitable for use with 3-cell NiCd or 1-cell Li-Ion

batteries. The device delivers +30dBm (1W) typical out-

put power from a +3.6V supply or +28dBm from a +2.7V

supply.

The MAX2235’s gain is adjustable over a 37dB range.

A power-control pin controls gain and bias to maintain

optimum efficiency, even at lower output power levels,

thus extending the operating life of the battery. At

+30dBm output power, efficiency is typically 47%. An

additional power-saving feature is a shutdown mode

that typically reduces supply current below 1µA.

A key feature of this PA is its autoramping capability.

During turn-on and turn-off periods, the RF envelope is

controlled to approximate a raised cosine on the rising

and falling edge, thereby minimizing transient noise

and spectral splatter. The ramp time is set by selecting

the value of an external capacitor.

The MAX2235 is intended for use in constant envelope

applications such as AMPS, two-way paging, or FSK-

based communications in the 900MHz ISM band. The

device is available in a thermally enhanced 20-pin

TSSOP package with a heat slug.

Applications

900MHz ISM-Band Applications

Two-Way Pagers

Analog Cellular Phones

Microcellular GSM (Power Class 5)

Wireless Data Networks

Features

♦ 800MHz to 1000MHz Operation

♦ High Output Power at 836MHz

+32.5dBm at +5.0V

+30dBm at +3.6V

+29dBm at +3.0V

+28dBm at +2.7V

♦ +2.7V to +5.5V Single-Supply Operation

♦ Automatic Power-Up/Power-Down Ramp

♦ Direct On/Off Keying (OOK) without Intersymbol

Interference or VCO Pulling

♦ 37dB Power-Control Range

♦ 47% Efficiency

♦ <1µA Supply Current in Shutdown Mode

♦ Small 20-Pin TSSOP Package with Heat Slug

MAX2235

+3.6V, 1W Autoramping Power

Amplifier for 900MHz Applications

________________________________________________________________ Maxim Integrated Products 1

SHDN

GND

GNDV

GND

RFIN

TOP VIEW

RFOUT

GND

GNDV

GND

REF

RAMPGND

MAX2235

TSSOP-EP

NOTE: THE GROUND OF THE OUTPUT STAGE IS CONNECTED TO THE

UNDERSIDE METAL SLUG.

MAX2235

SHDN

RFIN

RAMP

BIAS

REF

NOTE: SOLDER UNDERSIDE OF METAL SLUG TO BOARD GND PLANE.

RFOUT

GNDGND GND

15, 16

6, 7, 102

4 3 5 8, 9

13, 14, 17, 18, SLUG

VGA

Functional Diagram

19-1463; Rev 2; 10/00

PART

MAX2235EUP -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

20 TSSOP-EP

EVALUATION KIT

AVAILABLE

Pin Configuration

Ordering Information

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.

Summary of content (8 pages)

PAGE 1
9-1463; Rev 2; 10/00 KIT ATION EVALU E L B A AVAIL +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications The MAX2235 low-voltage, silicon RF power amplifier (PA) is designed for use in the 900MHz frequency band. It operates directly from a single +2.7V to +5.5V supply, making it suitable for use with 3-cell NiCd or 1-cell Li-Ion batteries. The device delivers +30dBm (1W) typical output power from a +3.6V supply or +28dBm from a +2.7V supply. The MAX2235’s gain is adjustable over a 37dB range.
PAGE 2
MAX2235 +3.6V, 1W Autoramping Power Amplifier for 900MHz Applications ABSOLUTE MAXIMUM RATINGS VCC to GND ...........................................................-0.3V to +6.5V SHDN to GND.............................................-0.3V to (VCC + 0.3V) GC to GND .................................................-0.3V to (VCC + 0.3V) RF Input Power .................................................+13dBm (20mW) Maximum Load Mismatch without Damage, VCC = +2.7V to +3.
PAGE 3
+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications (MAX2235 Evaluation Kit, GC = unconnected, PRFIN adjusted to give PRFOUT = +30dBm, fRFIN = 836MHz, VCC = V SHDN = +3.6V, TA = +25°C, unless otherwise noted.) (Note 3) PARAMETER Operational Frequency Range (Note 4) SYMBOL CONDITIONS MIN 800 fRFIN VCC = 5.0V PRFOUT Average Supply Current 27.0 VCC = 3.0V, TA = TMIN to TMAX 25.5 Power Gain 28.
PAGE 4
Typical Operating Characteristics (MAX2235 Evaluation Kit, GC = unconnected, fRFIN = 836MHz, VCC = V SHDN = +3.6V, TA = +25°C, unless otherwise noted.) OUTPUT POWER vs. VOLTAGE AT GC PIN 300 200 TA = +25°C 20 TA = +85°C 10 0 100 -10 0 -20 10 15 20 25 30 35 0 0.5 1.0 MAX2235 toc03 VCC = +2.7V 20 15 10 0 -25 2.
PAGE 5
+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications FALL TIME vs. RAMPING CAPACITANCE RISE TIME vs.
PAGE 6
+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications MAX2235 Typical Operating Circuit JU2 470pF 8.2nH 100pF J1 1 SMA 2 3 VCC 4 1000pF 5 22pF 100pF 100pF 6 7 8 VCC 100pF 1000pF RFIN GC GND SHDN VCC VCC GND MAX2235 GND VCC RFOUT GND RFOUT GND GND VCC GND VCC 1000pF 20 3 2 19 17 16 VCC 1500pF * 68pF J2 15 14 JU1 1000pF 1 470pF 18 SMA 47pF 11pF 13 9 V CC REF 12 10 GND RAMP 11 0.068µF J3 VCC J4 0.
PAGE 7
+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications Biasing and Power Control SHDN, GC, RAMP, and REF are bias and power-control pins. Drive SHDN below 0.5V to turn off the entire chip, and drive SHDN above 2.0V to turn on the device. When SHDN is high, a VGC from 0.6V to 2.3V continuously controls the gain in the first stage (VGA) and the output power. Drive GC below 0.4V to put the device in standby mode with only the first stage on. If GC is unconnected and V SHDN > 2.
PAGE 8
+3.6V, 1W Autoramping Power Amplifier for 900MHz Applications TSSOP.EPS MAX2235 Package Information 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.