92HD99B Datasheet, PDF (35/225 Pages) Integrated Device Technology – SINGLE CHIP PC AUDIO SYSTEM

92HD99
SINGLE CHIP PC AUDIO SYSTEM, CODEC+SPEAKER AMPLIFIER+CAPLESS HP+LDO
Figure 13. Aux Audio Playback when the System is Docked and Headphones are Plugged In
Playback Dock Headphone
D-MIC
MIC
HP
DM
A
B
S
HD Audio Interface
I2S
CODEC
I2S
Routing
Dock
F
HP
MIC
SPKR
D
EQ
S
NA
C
PC
Beep
Filter
EC
Aux Audio
Module
2.24.7. EAPD
Since the Aux Audio mode overrides the default behavior but not the actual port settings when in
reset, the logical state of the EAPD pin must be overridden as well. When Aux Audio mode is
enabled and the part is in reset as described above, the logical state of EAPD will be 1 (External
Amplifier Powered Up) unless held low by an external circuit. This ensures that audio pass-thru and
analog PC_Beep will be supported.
2.24.8. Analog PC_Beep
Analog PC_Beep is supported in Aux Audio mode. By default, analog PC_Beep is disabled but may
be enabled due to Beep pass-thru support in reset (see the PC_Beep section). If the CODEC is pro-
grammed to enable analog PC_Beep and Aux Audio mode is enabled, the next time reset is
asserted, the analog PC_Beep pin will be mixed at each of the active outputs.
2.24.9. Class-D BTL Issues
While in Aux Audio mode the HD Audio bus clock (BitClk) is not available. The Class-D controller
requires a very high speed clock to operate and an internal clock must be provided. In Aux Audio
mode, the actual frequency used by the Class-D controller and its associated ADC will not be exact
since an external reference will not be available.The performance characteristics in Aux Audio Mode
will be degraded compared to the normal operating mode characteristics specified elsewhere in this
document.
2.24.10. Firmware/Software Requirements:
The reconfiguration outlined in this chapter is autonomous (without the help of firmware or OS
driver.)
This autonomous mode does not interfere with normal operation.
If it is desirable to stop the HD Audio bus while the CODEC is in D3 under OS control per DCN
HDA015-B, no action is required. The CODEC will not enter Aux Audio Mode unless placed in
D3cold.
IDT™ CONFIDENTIAL
35
©2009 INTEGRATED DEVICE TECHNOLOGY, INC.
V1.2 1/12
92HD99