STAC9766 Datasheet, PDF (18/97 Pages) Integrated Device Technology – TWO-CHANNEL, 20-BIT, AC’97 2.3 CODECS WITH STEREO MICROPHONE AND MIC/JACK SENSING

STAC9766/9767
TWO-CHANNEL, 20-BIT, AC’97 2.3 CODECS WITH STEREO MICROPHONE AND MIC/JACK SENSING
PC AUDIO
3.1. Split Independent Power Supply Operation
In PC applications, one power supply input to the STAC9766/9767 may be derived from a supply
regulator 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 manufacturer's CODECs would
be subject to on-chip SCR type latch-up.
IDT’s STAC9766/9767 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 STAC9766/9767 is not designed to operate for extended periods with only the analog
supply active.
Note: Pin 48: To Enable SPDIF, use a 1 KΩ - 1 0 KΩ external pulldown. To Disable SPDIF, use a
1 KΩ - 1 0 KΩ external pullup. Do NOT leave Pin 48 floating.
Note: The CD_GND signal is an AC signal return for the two CD input channels. It is normally
biased at about 2.5V. The name of the pin in the AC97 specification is CD_GND, and this has
confused many designers. It should not have any DC path to GND. Connecting the CD_GND
signal directly to ground will change the internal bias of the entire CODEC, and cause significant
distortion. If there is no analog CD input, then this pin can be No-Connect.
IDT™
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TWO-CHANNEL, 20-BIT, AC’97 2.3 CODECS WITH STEREO MICROPHONE AND MIC/JACK SENSING
STAC9766/9767
V 7.4 12/06