Typical application circuit – Rainbow Electronics MAX7042 User Manual
Page 15
MAX7042
308MHz/315MHz/418MHz/433.92MHz
Low-Power, FSK Superheterodyne Receiver
______________________________________________________________________________________
15
Layout Considerations
A properly designed PC board 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 PC board trace adds about
20nH of parasitic inductance. The parasitic inductance
can have a dramatic effect on the effective inductance
of a passive component. For example, a 0.5in trace
connecting a 100nH inductor adds an extra 10nH of
inductance 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
DD
or HV
IN
connections.
31
30
29
28
27
26
9 10
11
12
13 14
15
18
19
20
21
22
23
24
7
6
5
4
C13
C14
C15
C6
Y1
C16
RF INPUT
C7
L1
RSSI
XTAL2
XTAL1
AV
DD
8
LNAIN
3.0V
LNASEL
D
ATA
HV
IN
V
DD
V
DD
FSEL2
FSEL1
EN
LNASEL
DATA
FSEL2
FSEL1
EN
DV
DD
DGND
DF
OP+
DS+
DS-
PDMAX
17
PDMIN
IFIN-
AGND
16
IFIN+
MIXOUT
MIXIN-
EXPOSED PADDLE
MIXIN+
LNAOUT
LNASRC
L3
L2
GND
Y2
OUT
IN
V
DD
V
DD
C10
C12
C11
C8
C9
C2
C1
C4
C5
R1
C3
V
DD
MAX7042
Typical Application Circuit