19-2416; Rev 2; 3/04
+14dBm to +20dBm LO Buffers/Splitters
with 1dB ꢀariation
General Description
Features
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.
✕ ±1dB Output Power Variation
✕ +14dBm to +20dBm Adjustable Output Power
✕ Two-Way Power Splitting
✕ 40dB Reverse Isolation
✕ More than 30dB Output-to-Output Isolation
✕ Low Output Noise: -170dBc/Hz at +17dBm
✕ 160mA Supply Current at +17dBm
✕ Isolated PLL Output (+3dBm)
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
✕
output-to-output port isolation, and are offered in 5mm
5mm 20-pin thin QFN packages with exposed paddle.
Applications
Ordering Information
Cellular/GSM/DCS/PCS/UMTS Base Station
Tx/Rx LO Drive
TEMP
RANGE
PIN-
PACKAGE
FREQUENCY
RANGE
PART
Base Station Main and Diversity Channels
Coherent Receivers
20 Thin
QFN-EP*
700MHz to
1100MHz
MAX9987ETP-T -40°C to 85°C
ISM Wireless LAN
20 Thin
QFN-EP*
1500MHz to
2200MHz
MAX9988ETP-T -40°C to 85°C
*EP = Exposed paddle.
Wireless Local Loop
Local Multipoint Distribution Service
Point-to-Point Systems
Typical Operating Circuit and Block Diagram
RF INPUT
(1)
OUTPUT AMP
(1)
PLL BUFFER
MAX9987
MAX9988
OUTPLL
(+3dBm)
TO PLL
PRESCALER
OUT1
(+17dBm)
IF OUTPUT
(1)
IN
(+7dBm)
RF INPUT
(2)
INPUT AMP
RF LO
PASSIVE TWO-WAY
POWER SPLITTER
OUT2
(+17dBm)
IF OUTPUT
(2)
BIAS
OUTPUT AMP
(2)
BIASIN
BIASOUT
BIAS
CONTROL
NETWORK
________________________________________________________________ Maxim Integrated Products
1
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.