Fuse state sense circuit
First Claim
1. A method for programming and sensing the state of a fusible link having a first intact state and a second open state, comprising the steps of:
- providing a fuse node, the fusible link connected between the fuse node and a low reference voltage level;
providing an output node having first and second logic states;
driving current through the output node and the fusible link from a high reference voltage level when the fusible link is in the first intact state, the step of driving pulling the output node to the low reference voltage level corresponding to the first logic state on the output node;
sensing the state of the fusible link by the step of applying a sense voltage from an external source to the fuse node, the sense voltage having a level above a predetermined threshold level but below a level that will cause damage to the fusible link, the step of applying the sense voltage substantially interrupting current through the output node such that the step of driving drives the output node to the high reference voltage level corresponding to the second logic state on the output node;
monitoring the output node to determine the state of the fusible link; and
removing the sense voltage from the fuse node without damaging the fuse after the step of monitoring.
1 Assignment
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Accused Products
Abstract
A fuse state sense circuit includes a fusible link (40) that is disposed between a node (38) and ground. A programming/sense pad (42) is provided to allow voltage to be applied to the node (38) external to the fuse state sense circuit. Current is provided to the node (38) through a current source (30) and a transistor (36). The transistor (36) is controlled by a bias current. An output node (32) is disposed between the current source (30) and the transistor (36). This is connected to the output through an inverter (34). In operation, the voltage on node (38) is raised to a first level to turn off transistor (36) to allow the output to be exercised and to change the state thereof to emulate the fusible link (40) being open. In a second and programming mode, the voltage on the node (38) is raised to a much higher level to allow sufficient current to flow through fusible link (40) to open it. Transistor ( 36) in this mode is rendered non-conductive and isolates the node (38) from the remaining portion of the circuit.
60 Citations
5 Claims
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1. A method for programming and sensing the state of a fusible link having a first intact state and a second open state, comprising the steps of:
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providing a fuse node, the fusible link connected between the fuse node and a low reference voltage level; providing an output node having first and second logic states; driving current through the output node and the fusible link from a high reference voltage level when the fusible link is in the first intact state, the step of driving pulling the output node to the low reference voltage level corresponding to the first logic state on the output node; sensing the state of the fusible link by the step of applying a sense voltage from an external source to the fuse node, the sense voltage having a level above a predetermined threshold level but below a level that will cause damage to the fusible link, the step of applying the sense voltage substantially interrupting current through the output node such that the step of driving drives the output node to the high reference voltage level corresponding to the second logic state on the output node; monitoring the output node to determine the state of the fusible link; and removing the sense voltage from the fuse node without damaging the fuse after the step of monitoring. - View Dependent Claims (2, 3, 4, 5)
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Specification