Method and circuit for maintaining I/O pad characteristics...

Details Method and circuit for maintaining I/O pad characteristics... Method and circuit for maintaining I/O pad characteristics...

2007-05-08

2007-05-08

Tan, Vibol (Department: 2819)

Electronic digital logic circuitry

Interface

Current driving

C326S080000, C326S081000, C327S112000, C327S333000

Reexamination Certificate

active

11047427

ABSTRACT:
A circuit implements a method to adjust input/output (I/O) characteristics of an I/O pad circuit (10) depending upon which value of an I/O supply voltage is used within a range of supply voltages. An I/O supply voltage being supplied to the pad circuit is detected by detecting (18, 20) its value relative to a known reference (16). Portions of the I/O pad circuit are selectively enabled in response to the detected I/O supply voltage. By selecting the ratio of P-channel and N-channel transistors, physical characteristics of the circuit are controlled. Examples of the controlled physical characteristics include slew rate, signal rise and fall times, and duty cycle control which is controlled by forcing all rising and falling edges to have a midpoint at the same point in time. Therefore a same I/O pad circuit may be optimally used in numerous applications regardless of the supply voltage value.

REFERENCES:
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patent: 6160430 (2000-12-01), Drapkin et al.
patent: 6512401 (2003-01-01), Clark et al.
patent: 6815998 (2004-11-01), Samad
patent: 7023238 (2006-04-01), Camarota
patent: 2003/0122574 (2003-07-01), Kushida
patent: 2004/0145388 (2004-07-01), Gallo et al.
patent: 2005/0046449 (2005-03-01), Davis
patent: 2005/0077929 (2005-04-01), Egerer et al.
patent: WO 97/21273 (1997-06-01), None

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