Enable circuit with embedded thermal turn-off
First Claim
1. An integrated enable circuit for providing a controlled output current, the enable circuit comprising:
- (a) a threshold circuit that provides the controlled output current when an ON/OFF input to the threshold circuit exceeds a predetermined threshold voltage, the threshold circuit including(i) first and second bipolar input transistors which operate at different current densities and which turn on in response to application of the predetermined threshold voltage;
(ii) a current mirror coupled between the first and second input transistors and a positive supply; and
(iii) switching means connected to the current mirror for providing the output biasing current when the current flowing in the first input transistor exceeds the current flowing in the second input transistor; and
(b) an embedded clamping network connected between the ON/OFF input to the threshold circuit and ground for turning off the controlled output current when the temperature of the threshold circuit exceeds a preselected temperature.
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Accused Products
Abstract
An enable circuit that integrates thermal shutdown capability. The enable circuit utilizes a temperature insensitive threshold detector network that provides a desired biasing current when the ON/OFF signal applied at its input exceeds a preselected voltage. Thermally sensitive circuitry connected between the input of the threshold detector network and ground remains off when the ON/OFF signal is equal to the preselected voltage and the temperature of the enable circuit is below a preselected maximum temperature. However, when the temperature of the enable circuit reaches the preselected maximum temperature, the thermally sensitive circuitry turns on, clamping the input signal to the threshold detector network below the preselected voltage.
21 Citations
6 Claims
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1. An integrated enable circuit for providing a controlled output current, the enable circuit comprising:
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(a) a threshold circuit that provides the controlled output current when an ON/OFF input to the threshold circuit exceeds a predetermined threshold voltage, the threshold circuit including (i) first and second bipolar input transistors which operate at different current densities and which turn on in response to application of the predetermined threshold voltage; (ii) a current mirror coupled between the first and second input transistors and a positive supply; and (iii) switching means connected to the current mirror for providing the output biasing current when the current flowing in the first input transistor exceeds the current flowing in the second input transistor; and (b) an embedded clamping network connected between the ON/OFF input to the threshold circuit and ground for turning off the controlled output current when the temperature of the threshold circuit exceeds a preselected temperature. - View Dependent Claims (2, 3, 4, 5)
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6. An integrated enable circuit for providing a controlled output current, the enable circuit comprising:
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(a) a threshold circuit that provides the controlled output current when an ON/OFF input to the threshold circuit exceeds a predetermined threshold voltage; (b) an embedded clamping network connected between the ON/OFF input to the threshold circuit and ground for turning off the controlled output current when the temperature of the threshold circuit exceeds a preselected temperature; and (c) a current regulator connected in parallel with the clamping network between the ON/OFF input signal and ground.
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Specification