General Description

The MAX9987 and MAX9988 LO buffers/splitters each

integrate a passive two-way power splitter with high-

isolation input and output buffer amplifiers. These

buffers are designed to provide the high output

(+14dBm to +20dBm) necessary to drive the LO inputs

of high-linearity passive mixers, while offering 40dB

reverse isolation to prevent LO pulling. The MAX9987 is

internally matched for the cellular/GSM bands, and the

MAX9988 is matched for the DCS/PCS/UMTS bands.

The typical application circuit provides a nominal

+17dBm output power with ±1dB variation over supply,

temperature, and input power. With two optional resis-

tors, the output power can be precision set from

+14dBm to +20dBm. The devices offer more than 30dB

5mm 20-pin QFN packages with exposed paddle.

Applications

Cellular/GSM/DCS/PCS/UMTS Base Station

Tx/Rx LO Drive

Base Station Main and Diversity Channels

Coherent Receivers

ISM Wireless LAN

Wireless Local Loop

Local Multipoint Distribution Service

Point-to-Point Systems

Features

o ±1dB Output Power Variation

o +14dBm to +20dBm Adjustable Output Power

o Two-Way Power Splitting

o 40dB Reverse Isolation

o More than 30dB Output-to-Output Isolation

o Low Output Noise: -170dBc/Hz at +17dBm

o 160mA Supply Current at +17dBm

o ESD Protection

o Isolated PLL Output (+3dBm)

+14dBm to +20dBm LO Buffers/Splitters

with ±1dB Variation

________________________________________________________________ Maxim Integrated Products

1

MAX9987

MAX9988

BIAS

BIASIN

RF LO

TO PLL

PRESCALER

PLL BUFFER

INPUT AMP

OUTPUT AMP

(2)

OUTPUT AMP

(1)

RF INPUT

(1)

IF OUTPUT

(1)

PASSIVE TWO-WAY

POWER SPLITTER

IN

(+7dBm)

OUTPLL

(+3dBm)

OUT1

(+17dBm)

OUT2

(+17dBm)

BIASOUT

BIAS

CONTROL

NETWORK

RF INPUT

(2)

IF OUTPUT

(2)

Typical Operating Circuit and Block Diagram

Ordering Information

19-2416; Rev 0; 4/02

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.

PART

TEMP

RANGE

PIN-

PACKAGE

FREQUENCY

RANGE

MAX9987EGP

-40

°C to 85°C 20 QFN-EP*

700MHz to

1100MHz

MAX9988EGP

-40

°C to 85°C 20 QFN-EP*

1500MHz to

2200MHz

*EP = Exposed paddle