tda5100a Infineon Technologies Corporation, tda5100a Datasheet - Page 22

• Manufacturer Part Number: tda5100a
• Description: Ask Transmitter 434 Mhz
• Manufacturer: Infineon Technologies Corporation

Wireless Components
4.4 Hints
1. Application Hints on the crystal oscillator
As mentioned before, the crystal oscillator achieves a turn on time less than
1 msec. To achieve this, a NIC oscillator type is implemented in the TDA 5100A.
The input impedance of this oscillator is a negative resistance in series to an
inductance. Therefore the load capacitance of the crystal CL (specified by the
crystal supplier) is transformed to the capacitance Cv.
Example:
Assume a crystal frequency of 13.56 MHz and a crystal load capacitance of
CL = 20 pF. The inductance L is specified within the electrical characteristics at
13.56 MHz to a value of 4.5 µ H. Therefore C6 is calculated to 12 pF.
CL:
ω :
L:
-R
4 - 5
crystal load capacitance for nominal frequency
angular frequency
inductance of the crystal oscillator
Cv
=
CL
Cv
L
1
IC
=
+
1
ω
CL
1
2
L
+
1
=
ω
f, CL Cv
C
2
L
6
Specification, March 2001
TDA 5100 A
Formula 1)
Applications
preliminary