dp83241 National Semiconductor Corporation, dp83241 Datasheet - Page 16

• Manufacturer Part Number: dp83241
• Description: Cdd Device Fddi Clock Distribution Device
• Manufacturer: National Semiconductor Corporation

5 0 Detailed Information
5 3 LAYOUT RECOMMENDATIONS
This drawing was done with convenience in mind
Note Pin 7 need not be hooked up






The part should be bypassed between the EXTV
EXTGND as close to the chip as possible (preferably un-
der the chip using chip caps) The part should also be
bypassed between the DV
chip as possible
The part should be bypassed between AV
as close to the chip as possible
No TTL logic lines should pass through the external crys-
tal or filter circuitry areas to avoid the possibility of noise
due to crosstalk
The filter circuitry should be connected to Ground on an
isolated branch off of the AGND pin
The DV
ed branch off of the EXTV
nected through a ferrite bead or small inductor
The AV
ed branch off of the DV
ed through a ferrite bead or small inductor
CC
CC
pin should be connected to V
pin should be connected to V
CC
CC
pin preferably being connect-
CC
and DGND as close to the
pin preferably being con-
(Continued)
CC
CC
FIGURE 5-10 Recommended Layout
CC
on an isolat-
on an isolat-
and AGND
CC
and
16







The external crystal circuitry should be connected to
Ground on an isolated branch off of the DGND pin
The DGND pin should be connected to Ground off of an
isolated branch of the EXTGND pin connected through a
ferrite bead or small inductor
The AGND pin should be connected to Ground off of an
isolated branch of the DGND pin connected through a
ferrite bead or small inductor
If the part is being driven by an external reference the
XTL IN pin should be tied to either GND or V
If using a multilayered board with dedicated V
Ground planes ensure that the external crystal circuitry
has its own small isolated ground island that is connect-
ed to the AGND DGND and EXTGND pins as described
above
See Figure 5 1 for component values
For best performance tie the VCORST pin to AGND
TL F 10385 – 15
CC
CC
and