8-134
RF9986
Rev B1 010717
8
Application Schematic
Pin
Function
Description
Interface Schematic
20
LNA OUT
LNA output pin. This is an open-collector output. This pin is typically
connected to pin 22 through a bias/matching inductor. This inductor, in
conjunction with a series blocking/matching capacitor, forms a match-
ing network to the 50
Ω image filter and provides bias (see Application
Schematic). The LNA’s IP3 may be increased 10dB by connecting pin
20 to VCC through the inductor. The LNA’s current then increases by
10mA. Other in-between IP3 vs. ICC trade-offs may be made by con-
necting resistance values between VCC and the matching inductor. The
two reference points for consideration are with 150
Ω used, which is
what connection to pin 22 achieves, the Input IP3 is +5.5dBm and the
LNA ICC is 5mA. Using no resistance, the Input IP3 is +15.5 dBm and
the LNA ICC is 15 mA. Desired operating points in between these val-
ues may be interpolated, roughly.
21
GND8
Same as pin 17.
22
VCC4
Output supply voltage for the LNA output (pin 20). This pin is typically
connected to pin 20 through a bias/matching inductor (see application
schematic). External RF bypassing is required. The trace length
between the pin and the bypass capacitor should be minimized. The
ground side of the bypass capacitor should connect immediately to
ground plane.
See pin 2.
23
GND9
Same as pin 17.
24
NC
No connection. This pin may be grounded (recommended) or left open.
LNA
OUT
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
V
CC
22 pF
LO BUFF EN
(On:
≥3.1 V;
Off:
≤0.5 V)
LO IN
V
CC
22 pF
2.7 nH
1.8 pF
RF Image
Filter, 50
Ω
22 pF
V
CC
C2
Filter
IF-
IF+
1nF
C1
L1
22 pF
C1
L1
1nF
V
CC
LO BUFF OUT
Z
FILTER =1 kΩ
Z
OUT =1 kΩ
Measurement
Reference Plane
L1 and C2 serve dual purposes. L1 serves as an output bias choke, and C2 serves as a series DC block. In addition, the
values of L1 and C2 may be chosen to form an impedance matching network if the IF filter's input impedance is not 1000
Ω.
Otherwise, the values of L1 and C1 are chosen to form a parallel-resonant tank circut at the IF when the IF filter's input
impedance is 1000
Ω.
RF IN
22 pF
C2
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