MICRF112 データシートの表示（PDF） - Micrel
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MICRF112 Datasheet PDF : 20 Pages
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Micrel, Inc.
Application Information
MICRF112
Note: Values in parenthesis are for 315MHz
Figure 6. ASK 433.92MHz and 315MHz
The MICRF112 is well suited to drive a 50 ohms source,
monopole or a loop antenna. Figure 6 is an example of a
loop antenna configuration. Figure 6 also shows both
315MHz and 433.92MHz ASK configurations for a loop
antenna. Besides using a different crystal, Table 1 lists
modified values needed for the listed frequencies.
Frequency
(MHz)
315.0
433.92
L1
C5
L4 C7 Y1 (MHz)
(nH) (pF) (nH) (p
F)
470
10
150 6.8 9.84375
680
10
82 4.7 13.5600
Table 1
The reference design shown in Figure 6 has an antenna
optimized for using the matching network as described in
Table 1.
Power Control Using External Resistor
R7 is used to adjust the RF output levels which may be
needed to meet compliance. As an example, the
following tables list typical values of conducted RF
output levels and corresponding R7 resistor values for
the 50Ω test board shown in Figure 2. R7 of the TX112
Demo board using the loop antenna can be adjusted for
the appropriate radiated field allowed by FCC or ETSI
compliance. Contact Micrel for suggested values to meet
FCC and ETSI compliances.
R7, Ω
0
75
100
500
1000
Output Power, dBm
10
8.5
8.0
1.6
-3.8
IDD, mA
6.7
6.3
6.2
4.13
4.87
Output Power Versus External Resistor at 315MHz
R7, Ω
0
75
100
500
1000
Output Power, dBm
8.68
8.34
8.02
4.34
0.42
IDD, mA
7.5
7.33
7.3
6.3
5.5
Output Power Versus External Resistor at 433.92 MHz
December 2011
14
M9999-120911
(408) 944-0800
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