Datasheet

LTC6945
24
6945f
APPLICATIONS INFORMATION
and Johanson Technology, can be attractive alternatives.
See Table 13 for recommended balun part numbers versus
frequency range.
The listed SMT baluns contain internal chokes to bias RF
±
and also provide input-to-output DC isolation. The pin
denoted as GND or DC FEED should be connected to the
V
RF
+
voltage. Figure 20 shows a surface mount balun’s
connections with a DC FEED pin.
Table 13. Suggested Baluns
f
RF
(MHz) PART NUMBER MANUFACTURER TYPE
350 to 900 #617DB-1673 TOKO TL
400 to 600 HHM1589B1 TDK SMT
600 to 1400 BD0810J50200 Anaren SMT
600 to 3000 MABACT0065 M/A-COM TL
1000 to 2000 HHM1518A3 TDK SMT
1400 to 2000 HHM1541E1 TDK SMT
1900 to 2300 2450BL15B100E Johanson SMT
2000 to 2700 HHM1526 TDK SMT
3700 to 5100 HHM1583B1 TDK SMT
4000 to 6000 HHM1570B1 TDK SMT
Figure 20. Example of a SMT Balun Connection
Figure 21. Example of a TL Balun Connection
The listed TL baluns do not provide input-to-output DC
isolation and must be AC coupled at the output. Figure 21
displays RF± connections using these baluns.
LTC6945
V
RF
+
RF
–
RF
+
TO 50Ω
LOAD
6945 F20
12
BALUN
23 1
54 6
11
BALUN PIN CONFIGURATION
1
2
3
4
5
6
UNBALANCED PORT
GND OR DC FEED
BALANCED PORT
BALANCED PORT
GND
NC
LTC6945
V
RF
+
RF
–
RF
+
TO 50Ω
LOAD
PRI
SEC
6945 F21
12
11
SUPPLY BYPASSING AND PCB LAYOUT GUIDELINES
Care must be taken when creating a PCB layout to mini-
mize power supply decoupling and ground inductances.
All power supply V
+
pins should be bypassed directly to
the ground plane using a 0.1μF ceramic capacitor as close
to the pin as possible. Multiple vias to the ground plane
should be used for all ground connections, including to
the power supply decoupling capacitors.
The package’s exposed pad is a ground connection, and
must be soldered directly to the PCB land. The PCB land
pattern should have multiple thermal vias to the ground
plane for both low ground inductance and also low thermal