Digital I/O and Clocking

Name

Pin

I / O

Functional Description

XTL_IN

2

I

24.576 MHz crystal input. Use a fundamental-mode type crystal. When operating from a

crystal, a 1M

Ω resistor must be connected across pins 2 and 3.

XTL_OUT

3

O

24.576 MHz crystal output. When operating from a crystal, a 1M

Ω resistor must be

connected across pins 2 and 3.

SDATA_OUT

5

I

This data stream contains both control data and DAC audio data. This input is sampled by

the LM4543 on the falling edge of BIT_CLK.

BIT_CLK

6

O

12.288 MHz clock which is derived (divide by two) from the 24.576MHz crystal input

(XTL_IN).

SDATA_IN

8

O

This data stream contains both control data and ADC audio data. This output is clocked out

by the LM4543 on the rising edge of BIT_CLK.

SYNC

10

I

48kHz sync pulse which signifies the beginning of both the SDATA_IN and SDATA_OUT

serial streams. SYNC must be synchronous to BIT_CLK.

RESET#

11

I

This active low signal causes a hardware reset which returns the control registers to their

default conditions.

Power Supplies and References

Name

Pin

I / O

Functional Description

AVDD

25,38

I

Analog supply pins.

AVSS

26,42

I

Analog ground pins.

DVDD

1,9

I

Digital supply pins.

DVSS

4,7

I

Digital ground pins.

VREF

27

O

Nominal 2.2V reference output. Not intended to sink or source current. Bypassing of this pin

should be done with short traces to maximize performance.

VREFOUT

28

O

Nominal 2.2V reference output. Can source up to 5mA of current and can be used to bias a

microphone. Do not connect any external capacitance to this pin.

AFILT1

29

O

This pin is not used and should be left open (NC). However, a capacitor to ground on this

pin is permitted as it will not affect performance.

AFILT2

30

O

This pin is not used and should be left open (NC). However, a capacitor to ground on this

pin is permitted as it will not affect performance.

3DP,3DN

31,32

O

These pins are used to complete the National 3D Sound circuit. Connect a 0.022µF

capacitor between pins 3DP and 3DN. The National 3D Sound can be turned on and off via

control register 20h. This is a fixed-depth type stereo enhance circuit, thus writing to register

22h has no effect. If National 3D Sound is not desired, then these pins should be left as no

connect (NC).

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