STAC9750 Datasheet, PDF (69/73 Pages) Integrated Device Technology – VALUE-LINE TWO-CHANNEL AC’97 CODECS

STAC9750/9751
VALUE-LINE TWO-CHANNEL AC’97 CODECS
PC AUDIO
14. APPENDIX A: SPLIT INDEPENDENT POWER SUPPLY OPERATION
In PC applications, one power supply input to the STAC9750/9751 may be derived from a supply
regulator (as shown in Figure 24) and the other directly from the PCI power supply bus. When power
is applied to the PC, the regulated supply input to the IC will be applied some time delay after the
PCI power supply. Without proper on-chip partitioning of the analog and digital circuitry, some manu-
facturer's CODECs would be subject to on-chip SCR type latch-up.
IDT’s STAC9750/9751 specifically allows power-up sequencing delays between the analog (AVddx)
and digital (VDddx) supply pins. These two power supplies can power-up independently and at dif-
ferent rates with no adverse effects to the CODEC. The IC is designed with independent analog and
digital circuitry that prevents on-chip SCR type latch-up.
However, the STAC9750/9751 is not designed to operate for extended periods with only the analog
supply active.
Note: Pin 48:
To Enable SPDIF, use a 1 KΩ-10 KΩ external pulldown.
To Disable SPDIF, use a 1 KΩ-10 KΩ external pullup.
Do NOT leave Pin 48 floating.
IDT™
VALUE-LINE TWO-CHANNEL AC’97 CODECS
69
STAC9750/9751
V 5.8 103106