CDCE62002 Datasheet, PDF (29/49 Pages) Texas Instruments – Four Output Clock Generator/Jitter Cleaner With Integrated Dual VCOs

CDCE62002
www.ti.com.............................................................................................................................................................. SCAS882A – JUNE 2009 – REVISED JULY 2009
Reference Input Buffer
Figure 22 shows the key elements of a Universal Input Buffer (UIB). A UIB supports multiple formats along with
different termination and coupling schemes. The CDCE62002 implements the UIB by including on board
switched termination, a programmable bias voltage generator, and a multiplexer. The CDCE62002 provides a
high degree of configurability on the UIB to facilitate most existing clock input formats.
REF_IN
PN
5k
Vbb
PP
5k
1 uF
Universal Input Control
Register 0
01
Register 0
01 45
Vbb
Input Buffer Select
Bit Name --> INBUFSELX _INBUFSELY
Register.Bit -->
0.0
0.1
0
0
0
1
1
0
1
1
Input Buffer
Mode
Disabled
LVPECL
LVDS
LVCMOS
0.0
INBUFSELX
X
0
1
0
1
Settings
0.1
0.4
INBUFSELY ACDCSEL
X
X
1
1
0
1
1
0
0
0
0.5
TERMSEL
1
0
0
0
0
SWITCH Status VBB
P N VBB
OFF OFF
ON ON
ON ON
ON ON
OFF
1.2V
1.2V
1.9V
ON ON 1.2V
Figure 22. CDCE62002 Universal Input Buffer
Smart Multiplexer Dividers
Register 0
23
REF_IN
Register 0
01
Pre-Divider
/1 or /2
Smart MUX
Control
Smart Multiplexer
Reference Divider
/1 - /8
Smart
MUX
Setting
REFSEL AUXSEL
Smart Mux
Mode
0.2
0.3
0
0 Reserved
1
0 _{REF Select}
0
1 ^{AUX Select}
1
1 Auto Select
XTAL /
AUX _IN
9
876
Register 0
Figure 23. CDCE62002 Smart Multiplexer
In Auto Select Mode the Smart Mux switches automatically between Reference input and Auxiliary input with a
preference to the Reference input. In order for the Smart Mux to function correctly the frequency after the
reference divider and the Auxiliary Input signal frequency should be within 20% of each other or one of them
should be zero or ground. In This mode a valid frequency needs to be present on AUX_IN before the /PD is
deasserted or power is applied.
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): CDCE62002
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