MAX2680 Ver la hoja de datos (PDF) - Maxim Integrated
Número de pieza
componentes Descripción
Lista de partido
MAX2680 Datasheet PDF : 12 Pages
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MAX2680/MAX2681/
MAX2682
Table 3. IFOUT Port Impedance
PART
MAX2680
MAX2681
MAX2682
45MHz
960-j372
934-j373
670-j216
FREQUENCY
70MHz
803-j785
746-j526
578-j299
240MHz
186-j397
161-j375
175-j296
Table 4. IF Output Impedance-Matching
Components
MATCHING
COMPONENT
L1
C2
R1
45MHz
390nH
39pF
250Ω
FREQUENCY
70MHz
330nH
15pF
Open
240MHz
82nH
3pF
Open
400MHz to 2.5GHz, Low-Noise,
SiGe Downconverter Mixers
Power-Supply Layout
To minimize coupling between different sections of the IC,
the ideal power-supply layout is a star configuration with
a large decoupling capacitor at a central VCC node. The
VCC traces branch out from this central node, each going
to a separate VCC node on the PC board. At the end of
each trace is a bypass capacitor that has low ESR at the
RF frequency of operation. This arrangement provides
local decoupling at the VCC pin. At high frequencies, any
signal leaking out of one supply pin sees a relatively high
impedance (formed by the VCC trace inductance) to the
central VCC node, and an even higher impedance to any
other supply pin, as well as a low impedance to ground
through the bypass capacitor.
Impedance-Matching Network Layout
The RFIN and IFOUT impedance-matching networks
are very sensitive to layout-related parasitics. To mini-
mize parasitic inductance, keep all traces short and
place components as close as possible to the chip. To
minimize parasitic capacitance, use cutouts in the ground
plane (and any other plane) below the matching network
components. However, avoid cutouts that are larger than
necessary since they act as aperture antennas.
Typical Operating Circuit
LO
INPUT
C1
1 LO
SHDN 6
MAX2680
MAX2681
MAX2682
2 GND
VCC 5
RF
Z1
INPUT
Z2
Z3
3 RFIN
4
IFOUT
SHUTDOWN
CONTROL
C3
L1
R1
C4
1000pF
C5
10µF
VCC
+2.7V TO +5.5V
IF
OUTPUT
C2
THE VALUES OF MATCHING COMPONENTS C2, L1, R1, Z1, Z2, AND Z3 DEPEND ON THE IF AND RF FREQUENCY AND DOWNCONVERTER. SEE TABLES 2 AND 4.
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