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.

Abstract: A voltage level shifting circuit (10) transitions an input signal at a first voltage to a second voltage higher than the first voltage. A cross-coupled latch provides the second voltage. Cascode configured transistors (16, 26) are connected in series with input transistors (18, 28) that receive the first voltage in complementary form. Capacitive devices (34, 40) are connected between the first voltage and gates of the cascode configured transistors for allowing independent small signal variations to occur on the gates of the cascode configured transistors for better control of duty cycle and rise and fall time matching of the level shifting circuit. Isolation devices (32, 38) permit independent modification of small signal voltages to occur on the gates of the cascode configured transistors.