CS4235 Datasheet, PDF (88/94 Pages) Cirrus Logic – CrystalClear Low Cost ISA Audio System

CS4235
CrystalClear ^TM Low Cost ISA Audio System
XTALO - Crystal Output
This pin is used for a crystal placed between this pin and XTALI. If an external clock is used
on XTALI, this pin must be left floating with no traces or components connected to it.
APSEL - Address Port Select, Input
This pin has an internal pull-up of approximately 100 kΩ. Leaving this pin in its default
condition, places the PnP/Crystal Key Address Port at the standard PnP address of 279h (hex).
For Motherboard applications, APSEL can be tied to SGND, which will change the Address
Port to one of two other addresses, chosen by a strapping option on pin SCL. When RESDRV
goes inactive, pin SCL is forced to an input and sampled. When SCL is sampled high (default),
the Address Port changes to address 308h. When SCL is sampled low, the Address Port changes
to 388h. Add-in cards should leave APSEL unconnected
TEST - Test
This pin must be tied to ground for proper operation.
Power Supplies
VA - Analog Supply Voltage
Supply to the analog section of the codec.
AGND - Analog Ground
Ground reference to the analog section of the codec. This pin should be placed on an analog
ground pin separate from other chip grounds.
VD1 - ISA Digital Supply Voltage
Digital supply for the ISA parallel data bus pins.
DGND1 - ISA Digital Ground
Digital ground reference for the ISA parallel data bus pins. These pins are isolated from the
other grounds and should be connected to the digital ground section of the board (see
Figure 24).
VDF1, VDF2, VDF3 - Digital Filtered Supply Voltage
Digital supply for the internal digital section of the codec (except for the parallel data bus).
These pins should be filtered, using a ferrite bead, from VD1.
SGND1, SGND2, SGND3, SGND4 - Internal Digital Grounds
Ground reference for the internal digital portion of the codec. Optimum layout is achieved by
placing SGND1/2/3/4 on the digital ground plane with the DGND pin as shown in Figure 24.
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