TDK5111 Просмотр технического описания (PDF) - Infineon Technologies

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производитель

TDK5111

ASK/FSK Transmitter 315 MHz

Infineon Technologies 

TDK 5111

Applications

4.5 Application Hints on the Crystal Oscillator

The crystal oscillator achieves a turn on time less than 1 msec when the

specified crystal is used. To achieve this, a NIC oscillator type is implemented

in the TDK 5111. 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.

-R

L

IC

f, CL Cv

Cv =

1

(1)

1 +ω2L

CL

CL: crystal load capacitance for nominal frequency

ω: angular frequency

L: inductance of the crystal oscillator

Example for the ASK-Mode:

Referring to the application circuit, in ASK-Mode the capacitance C7 is replaced

by a short to ground. Assume a crystal frequency of 9.84 MHz and a crystal load

capacitance of CL = 12 pF. The inductance L at 9.84 MHz is about 4.4 µH.

Therefore C6 is calculated to 10 pF.

Cv =

1

1 = C6

+ω2L

CL

Wireless Components

4-6

Specification, October 2002

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