POWER SUPPLIES AND REFERENCES

Name

Pin

I / O

Functional Description

AV

DD1

25

I

Analog supply

AV

SS1

26

I

Analog ground

AV

DD2

38

I

Analog supply 2

AV

SS2

42

I

Analog ground 2

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 (3.3 µF, 0.1 µF) 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 (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).

NC

29, 30

31, 32

43, 44

NC

These pins are not used and should be left open (NC).

For second source applications these pins may be connected to a noise-free supply or

ground (e.g. AV

Typical Performance Characteristics

ADC Noise Floor

DAC Noise Floor

20123715

20123716

www.national.com

14