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DECOUPLING APPLICATION NOTE
DECOUPLING APPLICATION NOTE
SONET/SDT/ATM S3025 Example
S3025
S3025
The S3025 Clock Recovery Unit (CRU) contains a stand-alone CRU PLL. The CAP1/CAP2 pins should be
connected to a 1.0
µF
capacitor in series with 68
Ω
resistors. Figure 1 illustrates the connections for the S3025
CRU device. The ground ring is shown around the loop filter capacitor. The ring should be attached to pin 19
(AGND) and brought to minimum metal spacing distance to pins 16 and 17. Please note that the ring should be
directly connected to the ground plane as close as possible to pin 19 to avoid current through the ground ring.
The values of the decoupling components are 0.1
µF
paralleled with 100 pF as shown below. The inductors are
Ferrite bead inductors which are Murata BLM31B601SPB or equivalent inductors.
Figure 1. Decoupling Layout
20
11
S3025
(TOP)
SERDATIP
SQUELCHN
SERDATIN
XTAL1
XTAL2
LCKREFN
AGND
DGND
1
DVCC
10
AVCC
+5 VOLT (VCC) PLANE
April 13, 2000 / Revision 1.0
SERCLKON
SERDATON
SERCLKOP
BYPASS
AGND
CAP1
CAP2
SD
SERDATOP
AVCC
1
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
