Current switching sensor detector
View Patent ↗A sensor for a switching circuit detects the logical state of the switching circuit by monitoring the current flow through the switching circuit. The current flow is conditioned by one or more current limiters and a voltage regulator, coupled in series with the switching circuit. The sensor also includes a current limit control circuit coupled to each of the current limiters. The sensor is effectively shielded from the effect of parasitic capacitance in the switching device because the current flow through the switching circuit reacts immediately and without regard to the level of parasitic capacitance whenever the switching circuit makes a state change.
1. A memory system comprising:
a plurality of content addressable memory (CAM) cells arranged into an array, each of said CAM cells further comprising a storage element and a match detection circuit for detecting a match between incoming data and data stored in said storage element, said match detection circuit further comprising:
a series circuit between a power terminal and a ground terminal, said series circuit including a current sensing amplifier, a logic switch, and a first current limiter coupled in series between said current sensing amplifier and said logic switch;
wherein a current flowing through said series circuit is affected by a state of said logic switch; and
wherein said current sensing amplifier detects the current flow and outputs a signal on a data terminal corresponding to the state of said logic switch.
2. The memory system of claim 1 , wherein the series circuit further comprises:
a current limiter control circuit coupled to the first current limiter to control current flow through said first current limiter.
3. The memory system of claim 1 , wherein the series circuit further comprises:
a voltage regulator coupled in series between said first current limiter and said logic switch.
4. The memory system of claim 3 , wherein said series circuit further comprises:
a second current limiter coupled in series between said logic switch and said ground terminal.
5. The memory system of claim 4 , wherein said current limiter control circuit is also coupled to the second current limiter to control current flow through said second current limiter.
6. A circuit for detecting a logical state of a switch circuit, comprising:
a series circuit between a power terminal and a ground terminal, said series circuit including a current sensing amplifier, said switch circuit, and a first current limiter coupled in series between said current sensing amplifier and said switch circuit; wherein
a current flowing through said series circuit is affected by a state of said switch circuit, and
said current sensing amplifier detects the current flow and outputs a signal on a data terminal corresponding to the state of said switch circuit.
7. The circuit of claim 6 , wherein the series circuit further comprises:
a current limiter control circuit coupled to the first current limiter to control current flow through said first current limiter.
8. The circuit of claim 7 , wherein the series circuit further comprises:
a voltage regulator coupled in series between said first current limiter and said switch circuit.
9. The circuit of claim 8 , wherein said series circuit further comprises:
a second current limiter coupled in series between said switch circuit and said ground terminal.
10. The circuit of claim 9 , wherein said current limiter control circuit is also coupled to the second current limiter to control current flow through said second current limiter.
11. The circuit of claim 9 , wherein said voltage regulator applies a charging current to the circuit.
12. The circuit of claim 11 , wherein the charging current is equal to the discharging current of the circuit.
13. The circuit of claim 9 , wherein the first current limiter is constructed to limit a charging current applied by the voltage regulator to the circuit.
14. The circuit of claim 13 , wherein the second current limiter is constructed to limit a discharge current flowing through the switch circuit.
15. The circuit of claim 9 , wherein each of said first and second current limiters consist essentially of a transistor and a device for supplying a gate signal to said transistor.