ASM2I9942C Datasheet, PDF (1/10 Pages) Alliance Semiconductor Corporation – Low Voltage 1:18 Clock Distribution Chip

May 2005
ASM2I9942C
rev 0.2
Low Voltage 1:18 Clock Distribution Chip
Features
ƒ LVCMOS/LVTTL Clock Input
ƒ 2.5V LVCMOS Outputs for Pentium II^TM*
Microprocessor Support
ƒ 150pS Maximum Targeted Output–to–Output Skew
ƒ Maximum Output Frequency of 250MHz @ 3.3 V_CC
ƒ 32–Lead TQFP and LQFP Packaging
ƒ Single 3.3V or 2.5V Supply.
ƒ Pin and Function compatible to MPC942C.
Functional Description
The ASM2I9942C is a 1:18 low voltage clock distribution
chip with 2.5V or 3.3V LVCMOS output capabilities. The
device is offered in two versions; the ASM2I9942C has an
LVCMOS input clock while the ASM2I9942P has an
LVPECL input clock. The 18 outputs are 2.5V or 3.3V
LVCMOS compatible and feature the drive strength to drive
50Ω series or parallel terminated transmission lines. With
output–to–output skews of 200pS, the ASM2I9942C is
ideal as a clock distribution chip for the most demanding of
synchronous systems. The 2.5V outputs also make the
device ideal for supplying clocks for a high performance
Pentium II ^TM microprocessor based design.
With a low output impedance (≈12Ω), in both the HIGH and
LOW logic states, the output buffers of the ASM2I9942C
are ideal for driving series terminated transmission lines.
With an output impedance of 12Ω, the ASM2I9942C can
drive two series terminated transmission lines from each
output. This capability gives the ASM2I9942C an effective
fanout of 1:36. The ASM2I9942C provides enough copies
of low skew clocks for most high performance synchronous
systems.
The LVCMOS/LVTTL input of the ASM2I9942C provides a
more standard LVCMOS interface. The OE pins will place
the outputs into a high impedance state. The OE pin has an
internal pullup resistor.
The ASM2I9942C is a single supply device. The V_CC power
pins require either 2.5V or 3.3V. The 32–lead TQFP and
LQFP package is chosen to optimize performance, board
space and cost of the device. The 32–lead TQFP has a
7x7mm² body size with a conservative 0.8mm pin spacing.
*Pentium II is a trademark of Intel Corporation
Alliance Semiconductor
2575, Augustine Drive • Santa Clara, CA • Tel: [phone] • Fax: [phone] • www.alsc.com
Notice: The information in this document is subject to change without notice.