2.5V or 3.3V, 200-MHz, 1:12 Clock Distribution Buffer
CY29948
Cypress Semiconductor Corporation
•
3901 North First Street
•
San Jose
•
CA 95134
•
408-943-2600
Document #: 38-07288 Rev. *B
Revised December 22, 2002
48
Features
• 2.5V or 3.3V operation
• 200-MHz clock support
• LVPECL or LVCMOS/LVTTL clock input
• LVCMOS-/LVTTL-compatible inputs
• 12 clock outputs: drive up to 24 clock lines
• Synchronous Output Enable
• Output three-state control
• 250 ps max. output-to-output skew
• Pin compatible with MPC948, MPC948L, MPC9448
• Available in Commercial and Industrial temp. range
• 32-pin TQFP package
Description
The CY29948 is a low-voltage 200-MHz clock distribution buff-
er with the capability to select either a differential LVPECL or
a LVCMOS/LVTTL compatible input clock. The two clock
sources can be used to provide for a test clock as well as the
primary system clock. All other control inputs are LVC-
MOS/LVTTL compatible. The 12 outputs are LVCMOS or LVT-
TL compatible and can drive 50
Ω series or parallel terminated
transmission lines. For series terminated transmission lines,
each output can drive one or two traces giving the device an
effective fanout of 1:24. The outputs can also be three-stated
via the three-state input TS#. Low output-to-output skews
make the CY29948 an ideal clock distribution buffer for nested
clock trees in the most demanding of synchronous systems.
The CY29948 also provides a synchronous output enable in-
put for enabling or disabling the output clocks. Since this input
is internally synchronized to the input clock, potential output
glitching or runt pulse generation is eliminated.
Block Diagram
Pin Configuration
PECL_CLK
PECL_CLK#
0
1
TCLK
TCLK_SEL
SYNC_OE
TS#
VDD
VDDC
12
Q0-Q11
CY29948
VSS
Q4
VDDC
Q5
VSS
Q6
VDDC
Q7
TCLK_SEL
TCLK
PECL_CLK
PECL_CLK#
SYNC_OE
TS#
VDD
VSS
1
2
3
4
5
6
7
8
24
23
22
21
20
19
18
17
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