TDA7100 Datasheet, PDF (28/41 Pages) Infineon Technologies AG – 434 MHz ASK/FSK Transmitter in 10-pin Package

TDA7100
C_L:
crystal load capacitance for nominal frequency
C₀:
shunt capacitance of the crystal
f:
frequency
ω:
ω = 2πf: angular frequency
N:
division ratio of the PLL
df:
peak frequency deviation
Applications
Because of the inductive part of the TDA7100, these values must be corrected by
Formula 1 on the preceding page. The value of Cv± can be calculated.
1
Cv± = _{1 + ω 2 L}
CL ±
If the FSK switch is closed, Cv- is equal to Cv1 (C1 in the application diagram). If the
FSK switch is open, Cv2 (C2 in the application diagram) can be calculated.
Csw:
Cv 2
=
C2
=
Csw
∗ Cv1 − (Cv +) ∗ (Cv1 +
(Cv +) − Cv1
Csw )
parallel capacitance of the FSK switch (3 pF incl. layout parasitics)
Remark: These calculations are only approximations. The necessary values depend
on the layout also and must be adapted for the specific application board.
3.8
Design Hints on the Clock Output (CLKOUT)
The CLKOUT pin is an open collector output. An external pull up resistor (RL) should be
connected between this pin and the positive supply voltage. The value of RL is
Data Sheet
28
V 1.0, 2007-05-02