Micrel, Inc.
MICRF002/RF022
Frequency
(MHz)
ZIN
Z11
Additional Applications Information
S11
LSHUNT(nH) LSERIES(nH)
In addition to the basic operation of the MICRF002 the
following enhancements can be made. In particular it is
strongly recommended that the antenna impedance is
matched to the input of the IC.
300
305
310
315
320
325
330
335
340
345
350
355
360
365
370
375
380
385
390
395
400
405
410
415
420
425
430
435
440
12-j166
12-j165
12-j163
13-j162
12-j160
12-j157
12-j155
12-j152
11-j150
11-j148
11-j145
11-j143
11-j141
11-j139
10-j137
10-j135
10-j133
10-j131
10-j130
10-j128
10-j126
10-j124
10-j122
10-j120
10-j118
10-j117
10-j115
10-j114
8-j112
0.803-j0.529
0.800-j0.530
0.796-j0.536
0.791-j0.536
0.789-j0.543
0.782-j0.550
0.778-j0.556
0.770-j0.564
0.767-j0.572
0.762-j0.578
0.753-j0.586
0.748-j0.592
0.742-j0.597
0.735-j0.603
0.732-j0.612
0.725-j0.619
0.718-j0.625
0.711-j0.631
0.707-j0.634
0.700-j0.641
0.692-j0.647
0.684-j0.653
0.675-j0.660
0.667-j0.667
0.658-j0.673
0.653-j0.677
0.643-j0.684
0.638-j0.687
0.635-j0.704
15
15
15
15
15
12
12
12
15
15
12
12
10
10
12
12
10
10
10
10
10
10
10
10
10
10
10
10
8.2
72
72
72
72
68
68
68
68
56
56
56
56
56
56
47
47
47
47
43
43
43
39
39
39
36
36
33
33
33
Antenna Impedance Matching
As shown in Table 4 the antenna pin input impedance is
frequency dependant. The ANT pin can be matched to 50Ω
with an L-type circuit. That is, a shunt inductor from the RF
input to ground and another in series from the RF input to
the antenna pin.
Inductor values may be different from table depending on
PCB material, PCB thickness, ground configuration, and
how long the traces are in the layout. Values shown were
characterized for a 0.031 thickness, FR4 board, solid
ground plane on bottom layer, and very short traces.
MuRata and Coilcraft wire wound 0603 or 0805 surface
mount inductors were tested, however any wire wound
inductor with high SRF (self resonance frequency) should
do the job.
Shutdown Function
Duty-cycled operation of the MICRF002 (often referred to
as polling) is achieved by turning the MICRF002 on and off
via the SHUT pin. The shutdown function is controlled by a
logic state applied to the SHUT pin. When VSHUT is high,
the device goes into low-power standby mode. This pin is
pulled high internally, it must be externally pulled low to
enable the receiver.
LSERIES
LSHUNT
Table 4. Input Impedance vs. Frequency
j100
j25
50
0
∞
–j25
–j100
M9999-070808
July 2008
11
MICREL [ MICREL SEMICONDUCTOR ]
