Abstract: An integrated circuit having input output buffers, where the integrated circuit is powered by at least a core power supply and an input output power supply. A level shifter receives an active low signal that indicates that the core power supply has powered down. The level shifter then outputs a known state upon receipt of the active low signal. A control circuit receives the known state form the level shifter, and then tristates the input output buffers upon receipt of the known state.

Abstract: A low-gain, low-jitter VCO circuit implemented in CMOS provides center frequency adjustment to overcome process variations. Further, noise immunity is improved by using a separate feedback loop to provide the nominal current biasing for the oscillator chain. This feedback loop coarsely sets the center frequency. The actual control of the oscillation frequency is achieved by a second current source, whose output is added to the nominal bias current to provide a total bias to the oscillator. This second current source "fine tunes" the oscillator frequency responsive to a control signal. Because two separate current sources are used, the circuit can realize a high oscillation frequency with a low VCO gain. Another feature provides for adjusting the center frequency in response to a digital input word provided via external pins, or from internal logic or memory. The center frequency thus can be calibrated by measurement at the time of manufacture, or changes later by the end user or by other circuitry.

Abstract: A circuit for sensing a parameter, such as temperature, has a single current source and a mismatched differential pair for providing two different currents at a desired current ratio. Each current is provided to a current control element and a sensing element, each of which may be diodes. An operational amplifier closes the loop and feeds back a signal from the input of the current control elements to the differential pair to hold the desired current ratio constant. Chopper circuitry is employed with the amplifier to reduce the offset and low frequency noise contribution of the amplifier.