Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Synchronizing
Patent
1998-07-14
2000-08-01
Kim, Jung Ho
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Synchronizing
327198, H03L 700
Patent
active
060972254
ABSTRACT:
A validity circuit is used with an analog circuit in a mixed signal system to determine whether the supply voltage is at an adequate voltage level to assure stable operation of the analog circuit. The validity circuit generates a "valid" signal that is used to activate the mixed signal system when the voltage level of the supply voltage is adequate. Where the voltage level of the supply voltage is inadequate to produce a stable output signal from the analog circuit, the analog circuit will stop generating a valid signal indicating that any output signal generated by the analog signal is unstable. The logic circuit is thus deactivated to avoid producing inaccurate or unreliable results. Where the analog circuit is a bandgap voltage reference circuit, the validity circuit is connected to two nodes within the feedback loop of the bandgap voltage reference circuit. By comparing the voltage levels of the two nodes, the validity circuit can determine when the feedback loop is going into an overdrive condition indicating that the supply voltage is no longer adequate to maintain a linear output signal from the bandgap voltage reference circuit. Each sub-system of the mixed signal system may have a separate validity circuit to individually determine if the supply voltage is adequate for that sub-system to produce a stable output signal. The valid signals generated by each validity circuit are received by a logic gate that appropriately activates or deactivates the mixed signal system.
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Kim Jung Ho
National Semiconductor Corporation
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