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Abstract

A current metering circuit is configured as a single stage charge pump for limiting the current level applied to the tunneling regions of an integrated circuit, nonvolatile, floating gate memory cell. The current metering circuit includes a storage capacitor which has one plate pumped by a periodic signal. The other plate of the capacitor is charged from a voltage that is boot-strapped from the voltage that presently exists across the active tunneling region. More particularly, a high voltage is applied to the drain of a transistor whose gate is connected to the tunneling region. The source of this transistor is coupled to a plate of the storage capacitor. This source develops a voltage equal to the present voltage across the load less the turnon threshold of the transistor. When the periodic signal goes low, the storage capacitor is charged from the voltage appearing at the source of this transistor. When the periodic signal goes high, this transistor is biased to turn off and the capacitor discharges through a diode to develop the metered output current. The current amplitude is equal to the product of the capacitance of the storage capacitor, the change in voltage across the capacitor in each cycle and the frequency of the periodic signal.

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First Claim