Audio Codec '97

AC ‘97 Component Specification Revision 2.3 Rev 1.0

2.3.5 Filter/References

These signals are connected to resistors, capacitors, or specific voltages.

Pin Signal Name Type Description

27 Vref O Reference Voltage

28 Vrefout O Reference Voltage out 5mA drive (intended for mic bias)

29 AFILT1 O Anti-Aliasing Filter Cap - ADC channel

30 AFILT2 O Anti-Aliasing Filter Cap - ADC channel

31 AFILT3 O Anti-Aliasing Filter Cap - optional Mic ADC channel

31 CAP1 O Generic Cap

32 CAP2 O Generic Cap

33 CAP3 O Generic Cap

34 CAP4 O Generic Cap

43 CAP5 O Generic Cap

44 CAP6 O Generic Cap

Table 6. Filtering and Voltage Reference Signal List

The generic capacitor pins can be used internally to support 3D stereo enhancement, tone control, or other vendor-

specific functions. The AC ‘97 vendor determines the specific use of each capacitor pin. However, to support a

vendor-independent AC ‘97 layout, the following are recommended:

• Internal functions which use generic capacitors between pins should use odd-even (n, n+1) cap pairs,

(1-2, 3-4, 5-6, etc.)

• Internal functions that use generic capacitor to ground may use any cap

• Generic capacitor values should be no greater than 1uF (0805 package or smaller is preferred)

To configure capacitor to gnd:

a = capacitor, b = open

To configure capacitor pin to pin:

a = open, b = capacitor

Figure 5. Example of vendor-independent external capacitor layout connection.