Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Having specific delay in producing output waveform
Patent
1993-02-08
1995-08-22
Hudspeth, David R.
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Having specific delay in producing output waveform
327284, 326 26, 326 83, H03K 513
Patent
active
054444063
ABSTRACT:
A variable drive strength buffer circuit is provided that automatically adjusts its associated drive strength to compensate for variations in manufacturing parameters, environmental conditions and operating conditions. As a result, electromagnetic interference, power supply noise, edge rates and ringing may be reduced. The self-adjusting variable drive buffer circuit may be fabricated on an integrated circuit and includes a speed detector unit that measures the relative speed of the integrated circuit. In one embodiment, a self-adjusting variable drive strength buffer circuit includes a circuit speed detector unit having a delay chain consisting of a plurality of variable delay elements. When the delay chain length is matched to the period of an input clock, the length of the chain is an accurate measure of the relative "speed" of the transistors making up the delay chain and therefore of the other transistors on the integrated circuit chip. The length of the delay chain is encoded into a vector (one or more digital bits of information) that controls the amount of drive that is provided in the variable drive buffer circuit. More drive is provided if the transistors on the chip are relatively slow and less drive is provided if the transistors are relatively fast.
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Advanced Micro Devices , Inc.
Hudspeth David R.
Sanders Andrew
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