DIGITAL I/O AND CLOCKING (Continued)

Name

Pin

I / O

Functional Description

RESET#

11

I

Cold Reset

This active low signal causes a hardware reset which returns the control registers and all

internal circuits to their default conditions. RESET# MUST be used to initialize the LM4549B

after Power On when the supplies have stabilized. Cold Reset also clears the codec from

both ATE and Vendor test modes. In addition, while active, it switches the PC_BEEP mono

input directly to both channels of the LINE_OUT stereo output.

ID0#

45

I

Codec Identity

ID1# and ID0# determine the Codec Identity for multiple codec use. The Codec Identity

configures the codec in either Primary or one of three Secondary Codec modes. These

Identity pins are of inverted polarity relative to the Codec Identity bits ID1, ID0 (bits D15, D14)

in the read-only Extended Audio ID register, 28h. If the ID0# pin (pin 45) is connected to

ground then the ID0 bit (D14, reg 28h) will be set to “1”. Similarly, connection to DV

the ID0 bit to “0”. If left open (NC), ID0# is pulled high by an internal pull-up resistor.

ID1#

46

I

Codec Identity

ID1# and ID0# determine the codec address for multiple codec use. The Codec Identity

configures the codec in either Primary or one of three Secondary Codec modes. These

Identity pins are of inverted polarity relative to the Codec Identity bits ID1, ID0 (bits D15, D14)

in the read-only Extended Audio ID register, 28h. If the ID1# pin (pin 46) is connected to

ground then the ID1 bit (D15, reg 28h) will be set to “1”. Similarly, connection to DV

the ID1 bit to “0”. If left open (NC), ID1# is pulled high by an internal pull-up resistor.

EAPD

47

O

External Amplifier Power Down control signal

This output is set by the EAPD bit (bit D15) in the Powerdown Control/ Status register, 26h.

As with the other logic outputs, the output voltage is set by DV

connected to the shutdown pin on an external power amplifier. For normal operation the

default value of EAPD = 0 will enable the external amplifier allowing an input on PC_BEEP to

be heard during Cold Reset.

POWER SUPPLIES AND REFERENCES

Name

Pin

I / O

Functional Description

AV

DD

25

I

Analog supply

AV

SS

26

I

Analog ground

DV

DD1

1

I

Digital supply

DV

DD2

9

I

Digital supply

DV

SS1

4

I

Digital ground

DV

SS2

7

I

Digital ground

V

REF

27

O

Nominal 2.2 V internal reference

Not intended to sink or source current. Use short traces to bypass (3.3µF, 0.1µF) this pin to

maximize codec performance. See text.

V

REF_OUT

28

O

Nominal 2.2 V reference output

Can source up to 5 mA of current and can be used to bias a microphone.

3D SOUND AND NO-CONNECTS (NC)

Name

Pin

I / O

Functional Description

3DP, 3DN

33,34

O

These pins are used to complete the National 3D Sound stereo enhancement circuit. Connect

a 0.022 µF capacitor between pins 3DP and 3DN. National 3D Sound can be turned on and

off via the 3D bit (D13) in the General Purpose register, 20h. National 3D Sound uses a

fixed-depth type stereo enhancement circuit hence the 3D Control register, 22h is read-only

and is not programmable. If National 3D Sound is not needed, these pins should be left open

(NC).

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