AN2479

Design guidelines for PCB schematic and layout

Doc ID 12956 Rev 2

11/23

Main filter

The main filter is an L-C based Butterworth filter. The cutoff frequency must be chosen

between the upper limit of the audio band (~ 20 kHz) and the carrier frequency (384 kHz).

Figure 11.

Main filter

Figure 12.

Recommended power-up and power-down sequence

Table 2.

Recommended values

Rload

8 ohm

4 ohm

Lload

22 µH

10 µH

Cload

470 nF

1 µF

C damp-S

100 nF

220 nF

C damp-P

220 nF

220 nF

R damp

6.2

2.7

Rload

Cload

Lload

Lload

INxA

INxB

2

Π

2

*

*

*

----------------

-----------------

=

1

2

Π

*

2

load

*

*

*

-----------------------------------------------------------------------

=

1

22

Π

*

*

*

-----------------------------------------------------------------

=

C

----------------

-

Don

’t care

Don

’t care

CMD0

CMD1

CMD2

VCC

VDD_Di

XTI

Reset

PWD

T

T

Don

’t care

Don

’t care

CMD0

CMD1

CMD2

VCC

VDD_Di

XTI

Reset

PWD

T

T

Don’t care

TR = mimimum time between XTI master clock stable and Reset removal: 1 msec

TC = minimum time between Reset removal and I2C program, sequence start: 1msec

Note 1: clock stable means: fmax - fmin < 1 MHz

Note 2: No specific VCC and VDD_Dig turn-on sequence is required