4-73
RF2308
Rev B2 010228
4
Application Schematic
Pin
Function
Description
Interface Schematic
1RF IN
RF input pin. This pin is NOT internally DC blocked. A DC blocking
capacitor, suitable for the frequency of operation, should be used in
most applications. DC coupling of the input is not allowed, because this
will override the internal feedback loop and cause temperature instabil-
ity.
2GND
Ground connection. Keep traces physically short and connect immedi-
ately to ground plane for best performance.
3GND
Same as pin 2.
4GND
Same as pin 2.
5GND
Same as pin 2.
6GND
Same as pin 2.
7GND
Same as pin 2.
8RF OUT
RF output and bias pin. Biasing is accomplished with an external series
resistor and choke inductor to VCC. The resistor is chosen to set the DC
current into this pin to a desired level. At room temperature, this pin will
bias itself to 3.7V as long as the current is held between 20 and 65mA.
Thus the resistor value is determined by the following equation:
Care should also be taken in the resistor selection to ensure that the
current into the part never exceeds 65 mA over the planned oper-
ating temperature. This means that a resistor between the supply
and this pin is always required, even if a supply near 3.7V is available.
Because DC is present on this pin, a DC blocking capacitor, suitable for
the frequency of operation, should be used in most applications. The
supply side of the bias network should also be well bypassed.
R
V
SUPPL Y
3.7
–
()
I
CC
----------------------------------------
=
RF OUT
FIN
1
2
3
4
8
7
6
5
RF OUT
22 pF
22
Ω
10 nF
22 pF
47 nH
22 pF
RF IN
V
CC =5V
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