US5670799A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High voltage protection using SCRs
Assignee: Intersil Corp
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Filing: 1994-08-26
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Granted: 1997-09-23
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Expires: 2014-08-26
Abstract
Abstract A high voltage protection circuit includes breakdown networks for providing a discharge path between a pair of terminals of a circuit to be protected. Each network conducts current between a supply terminal and another terminal at a low threshold voltage value when power is removed from the supply terminal. The network increases the threshold value when power is applied to the supply terminal to prevent conduction through the breakdown network during normal operation of the circuit to be protected. In one implementation, the protection circuit includes anti-latching circuitry connected to the breakdown network for preventing the breakdown network from latching on after or during the time power is applied to the supply terminals. To minimize the degradation of DC operating characteristics, the leakage currents, due to the protection circuit, between the first terminal and the positive supply terminal, and between the first terminal and the negative supply terminal cancel each other. The protection circuit may be incorporated on the same substrate as the circuit to be protected or it may be incorporated on a separate substrate sharing a common housing with the circuit to be protected. Alternately, the protection circuit say be in its own housing with its external leads connected to the leads of a first housing including the circuit to be protected.
Inventors
- 👤 Gregg D. Croft
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 21:52
CPC Classifications
H; H10; H10D; H10D89/00; H10D89/60; H10D89/601; H10D89/711; H10W; H10W72/00; H10W72/50; H10W72/541; H10W72/5449
Claims Analysis
Total Claims: 36
Claim 1
Independent Claim
70 words
An overvoltage protection circuit, for a first terminal in a protected circuit connected to a source of power, the protection circuit comprising: breakdown means connected between the first terminal and the source of power; and the breakdown means having a first threshold value when power is not being supplied by the source of power and a second, higher threshold value when power is being supplied by the source of power.
Claim 2
Dependent Claim
70 words
An overvoltage protection circuit, for a first terminal in a protected circuit connected to a source of power, the protection circuit comprising: breakdown means connected between the first terminal and the source of power; and the breakdown means having a first threshold value when power is not being supplied by the source of power and a second, higher threshold value when power is being supplied by the source of power.
Claim 3
Dependent Claim
23 words
A protection circuit according to claim 1 including anti-latching means connected to said breakdown means for preventing said breakdown means from latching on.
Claim 4
Dependent Claim
26 words
A protection circuit according to claim 1 wherein said second threshold value is a voltage greater than the voltage being supplied by the source of power.
Claim 5
Dependent Claim
121 words
In an integrated circuit having a plurality of terminals including a power supply terminal, a method for protecting a first circuit path from damage due to electrostatic discharge between two of the terminals, comprising the steps of: providing a discharge path different from the first circuit path for conducting the electrostatic discharge between the two terminals, said discharge path requiring a first level of threshold voltage to effect conduction between the two terminals when power is not applied to the power supply terminal; and increasing the threshold voltage to a second level when power is applied to the power supply terminal to prevent conduction through the discharge path when the voltage between the two terminals is less than the second level.
Claim 6
Dependent Claim
121 words
In an integrated circuit having a plurality of terminals including a power supply terminal, a method for protecting a first circuit path from damage due to electrostatic discharge between two of the terminals, comprising the steps of: providing a discharge path different from the first circuit path for conducting the electrostatic discharge between the two terminals, said discharge path requiring a first level of threshold voltage to effect conduction between the two terminals when power is not applied to the power supply terminal; and increasing the threshold voltage to a second level when power is applied to the power supply terminal to prevent conduction through the discharge path when the voltage between the two terminals is less than the second level.
Claim 7
Dependent Claim
169 words
In an integrated circuit having a plurality of terminals including a supply terminal and a second terminal wherein the supply terminal is of equal potential or is positively biased with respect to the second terminal during circuit operation, a discharge current path for protecting the integrated circuit from damage which could otherwise result from an electrostatic discharge between the supply terminal and the second terminal, comprising: an SCR structure having four regions of adjoining semiconductor material of alternating conductivity type, said structure including a first p-type region connected to the supply terminal, a first n-type region connected to the second terminal, a second p-type region and a second n-type region adjoining one another and intermediate to the first p-region and the first n-region, the second n-region adjoining the first p-region and the second p-region adjoining the first n-region; said SCR structure providing a discharge current path between the supply terminal and the second terminal when a positive transient voltage is applied between the supply terminal and the second terminal.
Claim 8
Dependent Claim
169 words
In an integrated circuit having a plurality of terminals including a supply terminal and a second terminal wherein the supply terminal is of equal potential or is positively biased with respect to the second terminal during circuit operation, a discharge current path for protecting the integrated circuit from damage which could otherwise result from an electrostatic discharge between the supply terminal and the second terminal, comprising: an SCR structure having four regions of adjoining semiconductor material of alternating conductivity type, said structure including a first p-type region connected to the supply terminal, a first n-type region connected to the second terminal, a second p-type region and a second n-type region adjoining one another and intermediate to the first p-region and the first n-region, the second n-region adjoining the first p-region and the second p-region adjoining the first n-region; said SCR structure providing a discharge current path between the supply terminal and the second terminal when a positive transient voltage is applied between the supply terminal and the second terminal.
Claim 9
Dependent Claim
45 words
The discharge current path of claim 5 wherein the second n-region is connected to the supply terminal through a resistive device to prevent conduction through the discharge current path when the supply terminal is positively biased with respect to the second terminal during circuit operation.
Claim 10
Dependent Claim
54 words
The discharge current path of claim 6 wherein the second p-region is connected to a potential at least as negative with respect to the supply terminal as the second terminal to prevent the discharge current path from conducting when the supply terminal is positively biased with respect to the second terminal during circuit operation.
Claim 11
Dependent Claim
54 words
The discharge current path of claim 5 wherein the second p-region is connected to a potential at least as negative with respect to the supply terminal as the second terminal to prevent the discharge current path from conducting when the supply terminal is positively biased with respect to the second terminal during circuit operation.
Claim 12
Dependent Claim
169 words
In an integrated circuit having a plurality of terminals including a supply terminal and a second terminal wherein the supply terminal is of equal potential or is negatively biased with respect to the second terminal during circuit operation, a discharge current path for protecting the integrated circuit from damage which could otherwise result from an electrostatic discharge between the supply terminal and the second terminal, comprising: an SCR structure having four regions of adjoining semiconductor material of alternating conductivity type, said structure including a first n-type region connected to the supply terminal, a first p-type region connected to the second terminal, a second n-type region and a second p-type region adjoining one another and intermediate to the first n-region and the first p-region, the second p-region adjoining the first n-region and the second n-region adjoining the first p-region; said SCR structure providing a discharge current path between the supply terminal and the second terminal when a negative transient voltage is applied between the supply terminal and the second terminal.
Claim 13
Dependent Claim
169 words
In an integrated circuit having a plurality of terminals including a supply terminal and a second terminal wherein the supply terminal is of equal potential or is negatively biased with respect to the second terminal during circuit operation, a discharge current path for protecting the integrated circuit from damage which could otherwise result from an electrostatic discharge between the supply terminal and the second terminal, comprising: an SCR structure having four regions of adjoining semiconductor material of alternating conductivity type, said structure including a first n-type region connected to the supply terminal, a first p-type region connected to the second terminal, a second n-type region and a second p-type region adjoining one another and intermediate to the first n-region and the first p-region, the second p-region adjoining the first n-region and the second n-region adjoining the first p-region; said SCR structure providing a discharge current path between the supply terminal and the second terminal when a negative transient voltage is applied between the supply terminal and the second terminal.
Claim 14
Dependent Claim
45 words
The discharge current path of claim 9 wherein the second p-type region is connected to the supply terminal through a resistive device to prevent conduction-through the discharge current path when the supply terminal is negatively biased with respect to the second terminal during circuit operation.
Claim 15
Dependent Claim
56 words
The discharge current path of claim 10 wherein the second n-type region is connected to a reference potential at least as positive with respect to the supply terminal as the second terminal to prevent the discharge current path from conducting when the supply terminal is negatively biased with respect to the second terminal during circuit operation.
Claim 16
Dependent Claim
56 words
The discharge current path of claim 10 wherein the second n-type region is connected to a reference potential at least as positive with respect to the supply terminal as the second terminal to prevent the discharge current path from conducting when the supply terminal is negatively biased with respect to the second terminal during circuit operation.
Claim 17
Dependent Claim
56 words
A protection circuit, for a first circuit which has a plurality of terminals including positive and negative supply terminals, comprising: breakdown means connected to said plurality of terminals of the first circuit for providing a low impedance current path between any two of said terminals when a voltage between said two terminals exceeds a threshold value.
Claim 18
Dependent Claim
56 words
A protection circuit, for a first circuit which has a plurality of terminals including positive and negative supply terminals, comprising: breakdown means connected to said plurality of terminals of the first circuit for providing a low impedance current path between any two of said terminals when a voltage between said two terminals exceeds a threshold value.
Claim 19
Dependent Claim
38 words
A protection circuit according to claim 13 including means for increasing said threshold value when power is applied to one of the supply terminals to prevent conduction through said breakdown means during normal operation of the first circuit.
Claim 20
Dependent Claim
35 words
A protection circuit according to claim 13 including anti-latching means connected to said breakdown means for preventing said breakdown means from latching on after or during the time power is applied to said supply terminals.
Claim 21
Dependent Claim
50 words
A protection circuit according to claim 13 wherein said breakdown means includes a plurality of diodes interconnecting said terminals for providing a protective current path through at least one forward biased diode for any combination of signals on any pair of terminals when power is removed from said supply terminals.
Claim 22
Dependent Claim
37 words
A protection circuit according to claim 13 wherein said breakdown means includes a pair of diodes wherein the diodes provide equal and opposite currents to one of said terminals when power is applied to said supply terminals.
Claim 23
Dependent Claim
64 words
A protection circuit, for a first circuit which has a plurality of terminals including positive and negative supply terminals, comprising: breakdown means connected to said plurality of terminals of the first circuit for providing a low voltage-low impedance current path between two of said terminals when a voltage between said two terminals exceeds a low threshold value with power removed from said supply terminals.
Claim 24
Dependent Claim
64 words
A protection circuit, for a first circuit which has a plurality of terminals including positive and negative supply terminals, comprising: breakdown means connected to said plurality of terminals of the first circuit for providing a low voltage-low impedance current path between two of said terminals when a voltage between said two terminals exceeds a low threshold value with power removed from said supply terminals.
Claim 25
Dependent Claim
38 words
A protection circuit according to claim 18 including means for increasing said threshold value when power ms applied to one of the supply terminals to prevent conduction through said breakdown means during normal operation of the first circuit.
Claim 26
Dependent Claim
35 words
A protection circuit according to claim 18 including anti-latching means connected to said breakdown means for preventing said breakdown means from latching on after or during the time power is applied to said supply terminals.
Claim 27
Dependent Claim
46 words
A protection circuit according to claim 18 wherein said breakdown means includes diode means interconnecting said terminals for providing a forward biased diode protective current path through SCRs for any combination of signals on any pair of terminals when power is removed from said supply terminals.
Claim 28
Dependent Claim
37 words
A protection circuit according to claim 18 wherein said breakdown means includes a pair of diodes wherein the diodes provide equal and opposite currents to one of said terminals when power is applied to said supply terminals.
Claim 29
Independent Claim
138 words
A method of providing overvoltage protection for a first terminal in a circuit connected to a source of power in which a breakdown means is connected between the first terminal and the source of power, the method comprising the steps of: providing a path for a current from the first terminal to the source of power, the path having a first threshold value for effecting conduction therethrough when power is not supplied by the source of power and a second, higher threshold value when power is supplied by the source of power; increasing the threshold of the breakdown means to said second threshold value when power is supplied by the source of power to prevent conduction through the path when the voltage between the first terminal and the source of power is less than said second threshold value.
Claim 30
Independent Claim
138 words
A method of providing overvoltage protection for a first terminal in a circuit connected to a source of power in which a breakdown means is connected between the first terminal and the source of power, the method comprising the steps of: providing a path for a current from the first terminal to the source of power, the path having a first threshold value for effecting conduction therethrough when power is not supplied by the source of power and a second, higher threshold value when power is supplied by the source of power; increasing the threshold of the breakdown means to said second threshold value when power is supplied by the source of power to prevent conduction through the path when the voltage between the first terminal and the source of power is less than said second threshold value.
Claim 31
Dependent Claim
75 words
The protection circuit of claim 1 in combination with a housing with plural leads; wherein said protected circuit is operably connected to said leads and comprises a first integrated circuit within said housing; and wherein said breakdown means is operably connected to at least some of said leads and comprises a second integrated circuit within said housing discrete from said first integrated circuit for protecting said first integrated circuit from high voltages on said leads.
Claim 32
Dependent Claim
46 words
The protection circuit of claim 24 further comprising a plurality of additional breakdown means formed on integrated circuitry discrete from said first and second integrated circuits and operably connected to said first integrated circuit to provide further protection of the first integrated circuit from high voltage.
Claim 33
Dependent Claim
21 words
The protection circuit of claim 25 wherein said first integrated circuit is operably connected to said leads through said breakdown means.
Claim 34
Dependent Claim
128 words
The protection circuit of claim 1 further in combination with a first housing with a first plurality of leads; wherein said protected circuit is an integrated circuit in said first housing operably connected to said first plurality of leads, and further in combination with a second housing With a second plurality of leads; wherein said breakdown means is a second integrated circuit in said second housing and operably connected to said second plurality of leads; and wherein said first and second plurality of leads provide an operable connection between at least one terminal of said breakdown means and at least one terminal of said protected circuit and further connect positive and negative terminals of said protection circuit with positive and negative power supply terminals of said protected circuit.
Claim 35
Dependent Claim
41 words
The protection circuit of claim 27 further comprising additional breakdown means formed on integrated circuitry in said second housing, said additional breakdown means being operably connected to the leads of said second housing which are operably connected to said protected circuit.
Claim 36
Dependent Claim
14 words
The protection circuit of claim 27 wherein said protected circuit is an analog circuit.
References Cited (Backward Citations)
US4870530A
Cited
US5140401A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-09-22 | 2001-03-24 | 2001-09-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-09-22 | 2005-03-24 | 2005-09-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-09-22 | 2009-03-24 | 2009-09-23 | $7700.00 | Window Closed / Lapsed |