Integrated CMOS circuit comprising a substrate bias voltage generator
First Claim
1. An integrated CMOS circuit comprising a first substrate bias voltage generator, which can be driven by an external clock generator, which also controls further circuits in the integrated circuit, and a second substrate bias voltage generator, characterized in that said second substrate bias voltage generator comprises a substrate bias voltage pump for generating a substrate bias voltage, an integrated oscillator for driving said substrate bias voltage pump, switching means for switching said oscillator on and off, and a comparator circuit for comparing the substrate bias voltage with a reference voltage and providing an output to drive said switching means.
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Abstract
In CMOS integrated circuits, "latch-up" problems may arise if no special steps are taken. One way to counteract a "latch-up" state is to apply a substrate bias voltage. In an integrated circuit, an externally-clocked substrate bias voltage pump and a stand-by bias voltage generator are provided, the latter not being switched on until the substrate bias voltage becomes less negative than, for example, -2V. As a result, the integrated circuit becomes less sensitive to "latch-up", especially during measuring and testing procedures, in which no external clock signal is supplied.
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Citations
5 Claims
- 1. An integrated CMOS circuit comprising a first substrate bias voltage generator, which can be driven by an external clock generator, which also controls further circuits in the integrated circuit, and a second substrate bias voltage generator, characterized in that said second substrate bias voltage generator comprises a substrate bias voltage pump for generating a substrate bias voltage, an integrated oscillator for driving said substrate bias voltage pump, switching means for switching said oscillator on and off, and a comparator circuit for comparing the substrate bias voltage with a reference voltage and providing an output to drive said switching means.
- 4. An integrated CMOS circuit comprising a substrate and a substrate bias voltage generator, which includes a first junction point and an oscillator having an output, a capacitance coupled between said first junction point and said output, a first NMOS transistor connected as a diode between the first junction point and ground and a second NMOS transistor connected as a diode between the first junction point and the substrate, characterized in that the width/length ratio of the second transistor is substantially larger than the width/length ratio of the first transistor.
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