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MC33493DTB

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P22
PLL Tuned UHF Transmitter for Data Transfer Applications, Rev. 1.7
Complete Application Schematic and PCB for FSK Modulation
Freescale Semiconductor16
)
Figure 13 shows a two-button keyfob board. Size is 30 × 45 millimeters.
Figure 13. Two-Button Keyfob Board Layout
13 Complete Application Schematic and PCB for FSK
Modulation
Figure 14 shows a complete application schematic using a MC68HC908RK2 microcontroller. FSK modulation is selected,
f
carrier
= 433.92 MHz. C
1
capacitor can be removed if switch debounce is done by software.
Table 7. Typical Crystal Characteristics (SMD Package)
Parameter
NDK LN-G102-950
(for 315 MHz)
NDK NX8045GB/CSJ
S1-40125-8050-12
(for 434 MHz and 868 MHz)
NDK NX1255GA
(for 434 MHz and 868 MHz)
Unit
Load capacitance 12 12 12 pF
Motional capacitance 3.33 4.4 10.5 fF
Static capacitance 1.05 1.5 2.46 pF
Loss resistance 28 18.5 10 Ω
Complete Application Schematic and PCB for FSK Modulation
PLL Tuned UHF Transmitter for Data Transfer Applications, Rev. 1.7
Freescale Semiconductor 17
Figure 14. Application Schematic for FSK Modulation, Serial Configuration, 434 MHz Frequency Band
For 868 MHz band application, the input pin BAND must be wired to ground. See component description in Table 8.
Figure 15 shows the corresponding PCB layout.
Table 8. External Components Description for FSK
Component Function Value Unit
Y1 Crystal 315 MHz band: 9.84,
See Table 7
MHz
434 MHz band: 13.56,
see Table 7
MHz
868 MHz band: 13.56,
see Table 7
MHz
R1 RF output level setting
resistor (R
ext
)
12 kΩ
C3 Crystal load capacitor See Table 9 pF
C4 pF
C2 Power supply decoupling capacitor 22 nF
C6 100 pF
PLL Tuned UHF Transmitter for Data Transfer Applications, Rev. 1.7
Recommendations for FSK Modulation
Freescale Semiconductor18
Figure 15. Application PCB Layout for FSK Modulation, Serial Configuration, 434 MHz Frequency Band
Table 9 gives the measured FSK deviations respective to C3 and C4 capacitor values for three deviations. Crystal reference is
NDK NX8045GB/CSJ S1-40125-8050-12.
Another crystal reference, NDK NX1255GA (see Table 7), is enabled to reach higher deviation as mentioned on Table 10.
These results are due to the higher crystal motional capacitor.
14 Recommendations for FSK Modulation
FSK deviation is function of total load capacitance presented to the crystal. This load capacitance is constituted by various
contributors:
• the crystal characteristic, especially its static capacitance
• the external load capacitors (C3, C4 as defined in Figure 14 and Table 9)
• the device internal capacitance of pins XTAL0, XTAL1, CFSK
• the PCB track capacitance
The schematic given in Figure 16 shows a typical FSK application using serial capacitor configuration, where device pads and
PCB track capacitances are mentioned.
Table 9. Crystal Pulling Capacitor Values vs Carrier Frequency Total Deviation -1-
Carrier frequency
(MHz)
Carrier frequency total
deviation (kHz)
C3 capacitor (pF) C4 capacitor (pF)
Recommended
R_off value (kΩ)
434 45 4.7 6.8 10
70 2.2 10 —
100 1 15 22
868 90 4.7 6.8 10
140 2.2 10 —
200 1 15 22
Table 10. Crystal Pulling Capacitor Values vs Carrier Frequency Total Deviation -2-
Carrier frequency
(MHz)
Carrier frequency total
deviation (kHz)
C3 capacitor value
(pF)
C4 capacitor value
(pF)
Recommended
R_off value (kΩ)
434 150 1 27 —
868 300 1 27 —
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P22

MC33493DTB

Mfr. #:
Buy MC33493DTB
Manufacturer:
NXP / Freescale
Description:
RF Transmitter 315 434 868 MHz
Lifecycle:
New from this manufacturer.
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