Trimming circuit
First Claim
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1. A trimming circuit, comprising an antifuse capacitor, the antifuse capacitor having a first terminal connected to a ground rail, and a second terminal to which a voltage may be selectively applied to blow the capacitor, the circuit further comprising:
- a first transistor (T5) connected between a first supply voltage rail and the second terminal of the capacitor;
a current source, connected to the second terminal of the capacitor is not blown, the first transistor is saturated and draws a large base current, whereas, when the antifuse capacitor is blown, the first transistor is not saturated and draws a smaller base current; and
means for monitoring the base current of the first transistor to determine when the first transistor is saturated.
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Accused Products
Abstract
To monitor the state of an antifuse capacitor, a transistor is connected to the capacitor such that it saturates only when the capacitor is not blown. Monitoring the base current of the transistor allows the state of the capacitor to be monitored without needing to use a conventional high-voltage comparator.
23 Citations
7 Claims
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1. A trimming circuit, comprising an antifuse capacitor, the antifuse capacitor having a first terminal connected to a ground rail, and a second terminal to which a voltage may be selectively applied to blow the capacitor, the circuit further comprising:
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a first transistor (T5) connected between a first supply voltage rail and the second terminal of the capacitor; a current source, connected to the second terminal of the capacitor is not blown, the first transistor is saturated and draws a large base current, whereas, when the antifuse capacitor is blown, the first transistor is not saturated and draws a smaller base current; and means for monitoring the base current of the first transistor to determine when the first transistor is saturated. - View Dependent Claims (2, 3, 4)
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5. A trimming circuit, comprising an antifuse capacitor, and means for selectively applying a suitable voltage thereto to blow the antifuse capacitor, and further comprising:
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a first current mirror circuit, comprising first (T5) and second (T8) transistors, the first transistor (T5) being connected between one terminal of the antifuse capacitor and a supply voltage rail; a third transistor (T10), connected to the bases of the first and second transistors (T5, T8), such that the base currents of the first and second transistors flow therethrough; a current sink (T11), connected to receive the current flowing through the third transistor (T10); a fourth transistor (T12), with its collector-emitter path connected in series with a load element (R3) between the supply voltage rail and a ground rail, and with its base terminal connected to the connection of the third transistor (T10) and the current sink (T11); and an output terminal (I3) located between the load element and through transistor (T12). - View Dependent Claims (6)
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7. A method of monitoring the state of an antifuse capacitor, the antifuse capacitor having a first terminal connected to a ground rail, and a second terminal to which a voltage may be selectively applied to blow the capacitor, the circuit further comprising a current source, connected to the second terminal of the capacitor, the method comprising:
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connecting a first transistor (T5) between a first supply voltage rail and the second terminal of the capacitor, such that, when the antifuse capacitor is not blown, the first transistor is saturated and draws a large base current, whereas, when the antifuse capacitor is blown, the first transistor (T5) is not saturated and draws a smaller base current; and monitoring the base current of the first transistor (T5) to determine when the first transistor (T5) is saturated.
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Specification