82P33731_16 Datasheet, PDF (30/68 Pages) IDEA.lnc. – Synchronous Ethernet

82P33731 Datasheet
3.2.6 APLL3
The APLL3 is provided for a better jitter and wander performance of
the device differential output clocks OUT11 and OUT12.
APLL3 supports 3 clock modes: SONET, Ethernet, and Ethernet
LAN. The base frequency for the 3 clock modes are 622.08 MHz,
625 MHz, and 644.53125 MHz respectively. The clock mode selected is
determined by the crystal used for the APLL.
The APLL uses a crystal to generate the respective mode’s base fre-
quency. The supported crystal frequencies are 24.8832 MHz (SONET),
25 MHz (Ethernet) and 25.78125 MHz (Ethernet LAN). The APLL sup-
ports up to two crystal connections, allowing the APLL to support up to
two mode’s base frequencies.
The input of both APLL3 can be derived from one of the DPLL1 out-
puts by configuring internal registers as described in Table 11.
Table 11: APLL3 input selection
Crystal
24.88320
25.00000
25.78125
APLL3 Input APLL3_mux_cnfg[3:0] APLL3_div1_cnfg[7:0] APLL3_div2_cnfg[26:0]
8100 Hz from DPLL1
0x04
8000 Hz from DPLL1
0x04
7812.5 Hz from DPLL1
0x03
0x01
0x000012BF
0x01
0x000012FB
0x01
0x0000063F
APLL3_pd_sel[14:0]
0x0001
0x0001
0x0001
APLL3_pd_sel[14:0]
0x0C00
0x0C35
0x0CE4
3.2.6.1 External Crystals
Suggestions for crystal options and best matching to APR require-
ments, crystal tolerance considerations and budgets, component place-
ment and crystal wiring to achieve minimum capacity are fully detailed in
IDT AN-861, “Recommended Crystals and Layout Guidelines for IDT’s
VCXO-based Synchronization PLLs.
Table 12 shows IDT (Fox) Crystals that can be used with APLL3.
Table 12: IDT(FOX) Crystals
Fox Part Number
495-24.8832-2
495-25-141
495-25.78125-2
Frequency (MHz)
24.88320
25.00000
25.78125
Model Number
FX532B
FX532B
FX532B
©2016 Integrated Device Technology, Inc.
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Revision 5, December 8, 2016