Low voltage 1 : 10 CMOS clock driver
Rev. 01 — 13 December 2005
Product data sheet
1. General description
The PCK946 is a low voltage CMOS 1 : 10 clock buffer. The 10 outputs can be conﬁgured
into a standard fan-out buffer or into 1× and 1⁄2× combinations. The ten outputs were
designed and optimized to drive 50 Ω series or parallel terminated transmission lines.
With output-to-output skews of 350 ps, the PCK946 is ideal as a clock distribution chip for
synchronous systems which need a tight level of skew from a large number of outputs.
With an output impedance of approximately 7 Ω, in both the HIGH and LOW logic states,
the output buffers of the PCK946 are ideal for driving series terminated transmission lines.
More speciﬁcally, each of the 10 PCK946 outputs can drive two series terminated
transmission lines. With this capability, the PCK946 has an effective fan-out of 1 : 20 in
applications using point-to-point distribution schemes.
The PCK946 has the capability of generating 1× and 1⁄2× signals from a 1× source. The
design is fully static; the signals are generated and re-timed inside the chip to ensure
minimal skew between the 1× and 1⁄2× signals. The device features selectability to allow
the user to select the ratio of 1× outputs to 1⁄2× outputs.
Two independent LVCMOS/LVTTL compatible clock inputs are available. Designers can
take advantage of this feature to provide redundant clock sources or the addition of a test
clock into the system design. With the TCLK_SEL input pulled HIGH, the TCLK1 input is
All of the control inputs are LVCMOS/LVTTL compatible. The DSELn pins choose
between 1× and 1⁄2× outputs. A LOW on the DSELn pins will select the 1× output. The
MR/OE input will reset the internal ﬂip-ﬂops and 3-state the outputs when it is forced
The PCK946 is fully 3.3 V compatible. 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.
s 2 selectable LVCMOS/LVTTL clock inputs
s 350 ps output-to-output skew
s Drives up to 20 series terminated independent clock lines
s Maximum input/output frequency of 150 MHz
s 3-stateable outputs
s 32-lead LQFP packaging
s 3.3 V VCC supply voltage