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SigmaTel, Inc.
Data Sheet
STAC9721
45
04/07/00
04/07/00
Appendix A
SPLIT INDEPENDENT POWER SUPPLY OPERATION
In PC applications, one power supply input to the STAC9721/23 may be derived from a supply regulator
(as shown in Figure 3) 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.
SigmaTel’s STAC9721/23 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 different
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.
.
VIDEO_L
VIDEO_R
AUX_L
AFILT1
AFILT2
AVss1
AVss2
DVss1
DVss2
AVdd1
AVdd2
DVdd1
DVdd2
820pF
29
30
14
17
16
7
4
42
26
3
2
CAP2
XTL_OUT
XTL_IN
24.576MHz
32
1uF
SigmaTel
STAC9721/23
28
Vrefout
Vref
27
1uF
0.1uF
27pF
27pF
LINE_OUT_L
LINE_OUT_R
MONO_OUT
35
36
37
LINE_IN_R
24
LINE_IN_L
23
PHONE
13
PC_BEEP
12
MIC2
22
AUX_R
15
MIC1
21
6
5
8
11
10
SDATA_OUT
SDATA_IN
RESET
SYNC
BIT_CLK
CD_GND
CD_R
20
19
18
CD_L
Analog Gnd
Digital Gnd
NOTE: Pins 31, 33, 34, 40
43, 44, and 48 are No Connects
** Teminate ground
plane as close to power
supply as possible
LNLVL_OUT_L
LNLVL_OUT_R
39
41
46
45
CID1
CID0
820pF
APOP
EAPD
34
47
CAP1
31
CAP3
33
0.1uF
Optional Anti-Pop Circuit
100uF
10uF
27pF
22 ohms
EMI
Filter
0.1uF
10uF
1uF
0.1uF
0.1uF
0.1uF
25
38
1
9
3.3V or 5V ± 5%
3.3V or 5V ± 5%
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