MD59-0021SMB Ver la hoja de datos (PDF) - Tyco Electronics
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MD59-0021SMB Datasheet PDF : 5 Pages
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PCS CDMA LNA / Downconverter, 1.8—2.0 GHz
External Circuitry Parts List
Ref. Designation
Value
Purpose
C6, C10, C11, C14
C2, C5, C7, C12, C13, C15-
C17
C3
C1, C4
C8
C9
L1
L2
L3
R1
U1
33 pF RF Bypass
1000 pF RF / IF Bypass
15 pF
10 pF
1.5 pF
100 pF
27 nH
72 nH
6.8 nH
Rbias
IF Matching
Bypass, IF Matching
LNA Input Matching
RF Bypass
IF Matching
IF Amplifier Input Matching
LNA Input Matching
Optional resistor to increase bias
current in LNA
MD59-00021
LNA/Downconverter
U2
Saw Filter TX signals and image
Filter
J1
DC
10 PIN DC Connector
Connect
Operating Instructions
The MD59-0021 is a highly integrated MMIC downconverter
for the 1.8-2 GHz PCS band. The downconverter provides
exceptional RF performance while consuming low DC current
and is packaged in a low cost plastic package. It is ideal for light
weight battery operated portable radio systems.
The receive chain consists of an LNA, RFA, balanced mixer and
single-ended IF output buffer amplifier as shown in the block
diagram. Surface mount resistors, inductors and capacitors are
used in conjunction with the IC for optimum performance,
tunability and ease of use. A schematic showing the IC and
required external components is shown on the previous page.
The input of the LNA is matched externally with a series
inductor (L3) and a shunt capacitor (C8) to provide a low loss
match to the optimum noise impedance in the band of interest.
A high Q inductor such as Coilcraft’s 0603CS series must be
used if the specified noise figures are to be achieved. The series
capacitor C9 is a DC blocking capacitor whose value is not
critical (it should be ≥ 100pF) The LNA is nominally biased
with 13 mA to give an input IP3 of +6 dBm. An external
resistor R1, may be used to increase the LNA bias current and
thus increase the IP3. An external image reject filter is required
between the LNA output and RFA input to prevent
downconversion of noise at the image frequency to the IF. This
filter should have a 50Ω input and output impedance.
The mixer is a balanced resistive FET mixer which provides
exceptional linearity and isolation with low loss and no DC
current. An off-chip inductor, L, is required to match the output
of the mixer to the input of the IF buffer amplifier.
MD59-0021
Recommended PCB Configuration
Cross Section View
RF Traces +
Components
RF
Ground
DC
Routing
Customer
The IF output port is the open drain of the IF buffer amplifier.
This allows maximum flexibility of intermediate frequency and
also IF filter characteristics. A matching network such as that
shown on page 2 can be used to match from the output
impedance of the buffer to the input impedance of the filter at
the required frequency. The inductor also acts as a choke for the
DC supply line.
The LO input port is internally matched to 50Ω. An LO buffer
amplifier amplifies the -10 dBm input signal to the level
required to drive the mixer. Performance is optimum with a
drive level of -5 dBm
All DC supply lines must be properly bypassed at RF
frequencies to obtain optimum performance and at lower
frequency to maintain unconditional stability. Capacitors C1,
C6, C11 and C14 are RF bypass capacitors for the LNA, RFA
and LOA. The value and placement of these capacitors are
critical in determining the frequency response of these
amplifiers. Capacitor C10 is a source bypass capacitor for the
second stage of the low noise amplifier. The placement of this
capacitor will affect the gain of the LNA. For best performance,
all the RF bypass capacitors should be placed as shown in the
PCB drawing shown above. Capacitors C2, C5, C7, C12, C13
and C15 are 1000 pF low frequency DC supply bypass
capacitors. Their value and placement are less critical than the
other capacitors. However, for best results, these capacitors
should be located as close to the package leads as possible.
Specifications subject to change without notice.
V 2.0
North America: Tel. (800) 366-2266, Fax (800) 618-8883
Asia/Pacific: Tel.+81-44-844-8296, Fax +81-44-844-8298
Europe: Tel. +44 (1344) 869 595, Fax+44 (1344) 300 020
Visit www.macom.com for additional data sheets and product information.
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