mc33493a Freescale Semiconductor, Inc, mc33493a Datasheet - Page 18

• Manufacturer Part Number: mc33493a
• Description: Pll Tuned Uhf Transmitter For Data Transfer
• Manufacturer: Freescale Semiconductor, Inc

Recommendations for FSK Modulation
Table 9
NDK NX8045GB/CSJ S1-40125-8050-12.
Another crystal reference, NDK NX1255GA (see
These results are due to the higher crystal motional capacitor.
14
FSK deviation is function of total load capacitance presented to the crystal. This load capacitance is constituted by various
contributors:
The schematic given in
PCB track capacitances are mentioned.
18
Figure 15. Application PCB Layout for FSK Modulation, Serial Configuration, 434 MHz Frequency Band
•
•
•
•
Carrier frequency
Carrier frequency
gives the measured FSK deviations respective to C3 and C4 capacitor values for three deviations. Crystal reference is
the crystal characteristic, especially its static capacitance
the external load capacitors (C3, C4 as defined in
the device internal capacitance of pins XTAL0, XTAL1, CFSK
the PCB track capacitance
Recommendations for FSK Modulation
(MHz)
(MHz)
434
868
434
868
Table 10. Crystal Pulling Capacitor Values vs Carrier Frequency Total Deviation -2-
Table 9. Crystal Pulling Capacitor Values vs Carrier Frequency Total Deviation -1-
Figure 16
PLL Tuned UHF Transmitter for Data Transfer Applications, Rev. 2
Carrier frequency total
Carrier frequency total
deviation (kHz)
deviation (kHz)
shows a typical FSK application using serial capacitor configuration, where device pads and
100
140
200
150
300
45
90
70
Table
C3 capacitor value
7), is enabled to reach higher deviation as mentioned on
C3 capacitor (pF)
Figure 14
(pF)
4.7
2.2
4.7
2.2
1
1
1
1
and
Table
C4 capacitor value
C4 capacitor (pF)
9)
(pF)
6.8
6.8
10
15
10
15
27
27
Freescale Semiconductor
R_off value (kΩ)
R_off value (kΩ)
Recommended
Recommended
10
22
10
22
—
—
—
—
Table
10.