Oscillator controls (FSEL, OSEL)

TDA7478

8/11

Doc 10679 Rev 4

4

Oscillator controls (FSEL, OSEL)

Two different crystal frequencies can be used. The adaption of the internal clock divider to

the external crystal is achieved via the input pin FSEL. See the following table for reference.

A special mode is introduced to reduce EMI. With pin OSEL connected to GND the internal

oscillator is switched off and an external sinusoidal frequency could be applied on OSCIN.

The peak to peak voltage of this signal can be reduced down to 60 mV.

In this mode the frequency selection via FSEL is still active.

Suggested values of C1 and C2 are shown in the following table.

Table 6.

Crystal frequencies

Crystal

FSEL (pin configuration)

4.332MHz

8.664MHz

connected to GND or open

connected to Vs

Table 7.

C1 and C2 suggested value

Crystal

C1

C2

4.332MHz

8.664MHz

27pF

27pF

47pF

-