CS4298 Datasheet, PDF (40/52 Pages) Cirrus Logic – SoundFusion Audio/Modem Codec 97 (AMC 97)

CS4298
The Vrefout pin is typically 2.2 V and provides a common mode signal for single-supply external
circuits. Vrefout only supports light DC loads and should be buffered if AC loading is needed. For
typical use, a 0.1 µF in parallel with a 1 µF capacitor should be connected to Vrefout.
7.6 Power Supplies
The power supplies providing analog power should be as clean as possible to minimize coupling into
the analog section which could degrade analog performance. The pins AVdd1 and AVdd2 supply
power to all the analog circuitry on the CS4298. This 5 Volt analog supply should be generated from
a voltage regulator (7805 type) connected to a +12 Volt supply. This helps isolate the analog circuitry
from noise typically found on +5 V digital supplies which power many digital circuits in a PC envi-
ronment. A typical voltage regulator circuit for analog power using an MC78M05CDT is shown in
Figure 15.
The digital power pins DVdd1 and DVdd2 should be connected to the same digital supply as the AC
’97 Controller’s AC-Link interface. Since the digital interface on the CS4298 may operate at either
3.3 V or 5 V, proper connection of these pins will depend on the digital power supply of the AC ’97
Controller. connections (vias). The AC-Link digital interface connection traces should be routed
+5 V PCI
0.1 µF
1
DGND
VCC
5
SPDIFO 2
SN75179D
GND
4
DGND
12
1
374 ¹
4
90.9
2
DGND
J-RCA-R4-PCB
51
+5V_PCI
82
.1µF
DGND
DGND
SPDIFO 4
3
8.2K
2
1
5
DGND
6
TOTX-173 _DGND
Figure 14. IEC-958 Interface Examples
+12VD
MC78M05CDT
Y5V
0.1µF
1 _IN
+ _ELEC
10µF
OUT ³
GND
2
Y5V
0.1µF
+5VA
+ _ELEC
10µF
DGND
AGND
Figure 15. Voltage Regulator
40
DS315PP2