MC33493MOD434 Freescale Semiconductor, MC33493MOD434 Datasheet - Page 19

• Manufacturer Part Number: MC33493MOD434
• Description: BOARD EVALUATION FOR MC33493 TX
• Manufacturer: Freescale Semiconductor
• Type: Transmitterr

Specifications of MC33493MOD434

• Contents: Module and Misc Hardware
• For Use With/related Products: MC33493 434 MHz RF Module
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Device pad capacitance is defined by the package capacitance and by the internal circuitry. Typical capacitance values for these
pads are given in
Some realistic assumptions and measurements have been made concerning track parasitic capacitances for a 0.8 mm FR4
double side application PCB. They are given in
To achieve large deviations, this total load capacitance must be lowered. For a given crystal, the PCB must be carefully laid out
to reduce the capacitance of the tracks wired to XTAL0, XTAL1, and CFSK pins.
Recommendation: a R_off resistor can be added in parallel with the FSK switch to optimize the transient response of
demodulated signal.
the layout in
Freescale Semiconductor
Figure
Table
16. When used, this component can be soldered on top of C3.
Table 11
11.
Figure 16. Crystal Load Capacitance Contributors Schematic
PLL Tuned UHF Transmitter for Data Transfer Applications, Rev. 1.7
gives the optimized R_off values for two deviations. There is no footprint for R_off resistor on
Table 11. Pads and Tracks Parasitic Values
C_track_XTAL0
C_track_XTAL1
C_track_CFSK
C_pad_XTAL0
C_pad_XTAL1
C_pad_CFSK
Capacitance
Table 11
and the corresponding PCB layout is shown in figure
Value
1.5
1.5
1.5
1
1
1
Unit
pF
pF
pF
pF
pF
pF
Recommendations for FSK Modulation
Figure
17.
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