Patent ID: 6420924
Filing Date: 2002-07-16
Classification: H03K

Abstract:
A slew-controlled split-voltage output driver in a microprocessor, for providing an output signal referenced to a first power supply voltage, comprising:an output driver circuit, for driving the output signal to a low level, a high level, or a tri-state level, said output driver circuit comprising: a P-channel source transistor, coupled to the first power supply voltage; and an N-channel sink transistor, connected in series with said P-channel source transistor across the first power supply voltage; wherein the output signal is formed by the connection between drain nodes of said P-channel source and said N-channel sink transistors, and wherein said P-channel source transistor pulls the output signal up to the first power supply voltage, thereby referencing the output signal to the first power supply voltage; a driver control circuit, coupled to the first power supply voltage, for receiving an enable signal, and configured to employ said enable signal to control turn on and turn off of said N-channel sink transistor, wherein, to control turn on and turn off, said enable signal must switch to a level essentially equal to the first power supply voltage, said driver control circuit comprising: a first N-channel transistor, driven by said enable signal, configured to control turn off of said N-channel sink transistor; and slew control logic, coupled to said first N-channel transistor, and driven by said enable signal, configured to sense direction of said enable signal, and configured to turn on slowly and turn off quickly, thereby controlling turn on of said N-channel sink transistor; and a feedback-enhanced level translator circuit, coupled to said driver control circuit, for receiving an output state signal whose high-level state is essentially equal to a second power supply voltage, said second power supply voltage being at least one half of the first power supply voltage, wherein said feedback-enhanced level translator circuit generates said enable signal to said level essentially equal to the first power supply voltage, and wherein said feedback-enhanced level translator circuit isolates generation of said enable signal from operation of said driver control circuit, and wherein said enable signal is directly driven by said output state signal through a second N-channel transistor, said output state signal being applied to a source node of said second N-channel transistor.