i A PHYSICAL IMPLEMENTATION WITH CUSTOM LOW POWER ...

6.0 DELAY ELEMENTS FOR LOW POWER FABRIC
Delay elements are circuits that introduce a specific delay between the input and the output.
Delay elements are widely used in asynchronous or self-timed digital systems. For a self-timed
system, the delay element generates a task-complete signal to flag the completion of the task
[11][12].Delay elements are also used in circuits that perform mathematical computations like
the Discrete Cosine Transform [11] [13]. Delay elements are also used in Phase Locked
Loops(PLLs) and Delay Locked Loops (DLL) [11] [14].
Circuits can be designed to provide the specific delay as required. The challenge in
designing delay element circuits is to have circuits that show good signal integrity and low
power consumption. Also the circuits should show very little variation across supply voltage,
temperature and process. An exhaustive study on delay elements has been conducted in the past
to analyze the pros and cons of various delay elements. Some of the conventional delay elements
are the Transmission gate, Cascaded inverter chain, Voltage-Controlled delay elements, and
transmission gate with Schmitt trigger [15][16].
6.1 DELAY ELEMENT TOPOLOGIES
A wide variety of delay element topologies have been described in [15] [16]. Each of the delay
element topology has a unique delay, area, power and signal integrity characteristic.
79