18.3.2 Global Buffers

Global buffers are provided for use with low skew, high fanout nets, such as, clock and reset. They can be either driven from a pad or internally. If a global buffer is used internally, the pad can be used for other input signals.

A 500K global buffers have the following features:

  • 2.5 or 3.3 CMOS voltage levels
  • Optional pull-up resistor
  • ESD protection circuitry
  • Latch-up protection circuitry.
  • Multiplexed input for external or internal drive.

Global Buffer Naming Conventions

Four types of global buffers are available: standard global input buffers (GL), global buffers with independent input buffers (GLIB), global multiplexed input buffers (GLMIB) and global buffers with internal connection only (GLINT).

Global buffer names are composed of up to the following four parts:

  • The name base indicating the type of buffer (GL, GLIB, GLMIB for external buffers, GLINT for an internal connected global buffer)
  • The number code 25 or 33 indicating a 2.5 or 3.3 voltage level
  • A two character code indicating low power pad voltage (LP)
  • An optional one character code (U) designating a pull-up resistor (except GLINT). When there is no resistor, this code is omitted
GL25U
Global input buffer with 2.5 CMOS voltage levels and pull-up resistor.
GLIB33
Global buffer with 3.3 CMOS voltage levels input buffer and global buffer with input A.
GLMIBL33U
Global multiplexed input buffer with 3.3 CMOS voltage levels, active low enable and pull-up resistor.