MAX7042 Maxim Integrated Products, MAX7042 Datasheet - Page 15

• Manufacturer Part Number: MAX7042
• Description: 308MHz/315MHz/418MHz/433.92MHz Low-Power FSK Superheterodyne Receiver
• Manufacturer: Maxim Integrated Products

A properly designed PCB is an essential part of any
RF/microwave circuit. On high-frequency inputs and
outputs, use controlled-impedance lines and keep
them as short as possible to minimize losses and radia-
tion. At high frequencies, trace lengths that are on the
order of λ/10 or longer act as antennas.
Keeping the traces short also reduces parasitic induc-
tance. Generally, 1in of a PCB trace adds about 20nH
of parasitic inductance. The parasitic inductance can
RF INPUT
Low-Power, FSK Superheterodyne Receiver
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Layout Considerations
308MHz/315MHz/418MHz/433.92MHz
L1
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L3
RSSI
XTAL2
XTAL1
AV
LNAIN
9 10
DD
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L2
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MAX7042
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have a dramatic effect on the effective inductance of a
passive component. For example, a 0.5in trace con-
necting a 100nH inductor adds an extra 10nH of induc-
tance or 10%.
To reduce the parasitic inductance, use wider traces
and a solid ground or power plane below the signal
traces. Also, use low-inductance connections to ground
on all GND pins, and place decoupling capacitors
close to all V
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IN
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GND
Y2
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PDMAX
DD
PDMIN
DGND
Typical Application Circuit
DV
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OUT
OP+
DS+
DS-
DF
DD
or HV
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IN
connections.
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R1
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