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PCK940L Datasheet, PDF (1/16 Pages) NXP Semiconductors – Low voltage 1 : 18 clock distribution chip | |||
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PCK940L
Low voltage 1 : 18 clock distribution chip
Rev. 01 â 4 April 2006
Product data sheet
1. General description
The PCK940L is a 1 : 18 low voltage clock distribution chip with 2.5 V or 3.3 V LVCMOS
output capabilities. The device features the capability to select either a differential
LVPECL or an LVCMOS compatible input. The 18 outputs are 2.5 V or 3.3 V LVCMOS
compatible and feature the drive strength to drive 50 ⦠series or parallel terminated
transmission lines. With output-to-output skews of 150 ps, the PCK940L is ideal as a clock
distribution chip for the most demanding of synchronous systems. The 2.5 V outputs also
make the device ideal for supplying clocks for a high performance microprocessor based
design.
With a low output impedance of approximately 20 â¦, in both the HIGH and LOW logic
states, the output buffers of the PCK940L are ideal for driving series terminated
transmission lines. With an output impedance of 20 â¦, the PCK940L has the capability of
driving two series terminated transmission lines from each output. This gives the
PCK940L an effective fan-out of 1 : 36. If a lower output impedance is desired, please see
the PCK942C data sheet.
The differential LVPECL inputs of the PCK940L allow the device to interface directly with a
LVPECL fan-out buffer like the PCKEP111 to build very wide clock fan-out trees or to
couple to a high frequency clock source. The LVCMOS input provides a more standard
interface for applications requiring only a single clock distribution chip at relatively low
frequencies. In addition, the two clock sources can be used to provide for a test clock
interface as well as the primary system clock. A logic HIGH on the LVCMOS_CLKSEL pin
will select the LVCMOS level clock input. All inputs of the PCK940L have internal
pull-up/pull-down resistors so they can be left open if unused.
The PCK940L is a single or dual supply device. The device power supply offers a high
degree of ï¬exibility. The device can operate with a 3.3 V core and 3.3 V output, a 3.3 V
core and 2.5 V outputs, as well as a 2.5 V core and 2.5 V outputs. 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 à 7 mm body size with a conservative 0.8 mm pin
spacing.
2. Features
I LVPECL or LVCMOS clock input
I 2.5 V LVCMOS outputs for Pentium II microprocessor support
I 150 ps maximum output-to-output skew
I Maximum output frequency of 250 MHz at 3.3 V VCC
I 32-lead LQFP packaging
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