1. General description
The PCK942P is a 1 : 18 low voltage clock distribution chip with 2.5 V or 3.3 V LVCMOS
output capabilities. The device is offered in two versions: the PCK942C has an LVCMOS
input clock, while the PCK942P has a LVPECL input clock. The 18 outputs are 2.5 V or
3.3 V LVCMOS compatible and feature the drive strength to drive 50 Ω series-terminated
transmission lines. With output-to-output skews of 200 ps, the PCK942P is ideal as a
clock distribution chip for the most demanding of synchronous systems. The 2.5 V output
also makes the device ideal for supplying clocks for a higher performance Pentium II
microprocessor-based design.
With a low output impedance of approximately 12 Ω, in both the HIGH and LOW logic
states, the output buffers of the PCK942P are ideal for driving series-terminated
transmission lines. With an output impedance of 12 Ω, the PCK942P can drive two
series-terminated transmission lines from each output. This capability gives the PCK942P
an effective fan-out of 1 : 36. The PCK942P provides enough copies of low skew clocks
for most high performance synchronous systems.
The differential LVPECL inputs of the PCK942P allow the device to interface directly with a
LVPECL fan-out buffer like the MC100EP111 to build very wide clock fan-out trees or to
couple to a high frequency clock source. The OE pin will place the outputs to a
high-impedance state. The OE pin has an internal pull-up resistor.
The PCK942P is a single supply device. The V
CC
power pins require either 2.5 V or 3.3 V.
The 32-lead LQFP package was chosen to optimize performance, board space, and cost
of the device. The 32-lead LQFP package has a 7 mm × 7 mm body size with a
conservative 0.8 mm pin spacing.
2. Features
■ LVPECL clock input
■ 2.5 V LVCMOS outputs for Pentium II microprocessor support
■ 200 ps maximum targeted output-to-output skew
■ Maximum output frequency of 250 MHz at 3.3 V V
CC
■ 32-lead LQFP packaging
■ Single 3.3 V or 2.5 V supply voltage
PCK942P
Low voltage 1 : 18 clock distribution chip
Rev. 01 — 17 February 2006 Product data sheet
