US5530612A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrostatic discharge protection circuits using biased and terminated PNP transistor chains
Assignee: Intel Corp
•
Filing: 1994-03-28
•
Granted: 1996-06-25
•
Expires: 2014-03-28
Abstract
Abstract In device requiring ESD protection, a bias network is used to augment the diode string to distribute small but significant forward current to the diodes. Also employed is the use of cantilever diodes which provide PNP Darlington gain block for ESD protection rather than for amplifying signals in bipolar ICs. In one embodiment, the termination is the principal element of device novelty and that which makes the protection device "stand-alone". The termination supplies final base current to the gain block for a limited amount of time, so that ESD charge can be shunted harmlessly through the PNP chain, but assures that the structure draws no current from a stable power supply long term. The entire structure is able to absorb noise spikes as well as ESD pulses. The termination also makes provisions for discharging its capacitor between ESD pulses, as is necessary for standardized testing. The invention has value as an IC power supply clamp, and reduces the damage often seen on IC power supplies during extensive ESD testing.
Inventors
- 👤 Timothy J. Maloney
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 20:14
CPC Classifications
H; H10; H10D; H10D89/00; H10D89/60; H10D89/601; H02; H02H; H02H7/00; H02H7/20; H02H7/205; H10D89/611; H10D89/711
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
185 words
A device for protecting an integrated circuit having an input/output buffer against electrostatic discharge, said input/output buffer including a first diode (22) having its anode coupled to a pad of said integrated circuit and its cathode coupled to a first peripheral supply potential, a second diode (24) having its anode coupled to an input node of said integrated circuit and its cathode coupled to a first internal supply potential, a third diode (23) having its anode coupled to a second internal supply potential and its cathode coupled to said input node, a fourth diode (25) having its anode coupled to said second internal supply potential and its cathode coupled to a second peripheral supply potential, and a resistance (37) connected between said pad and said input node of said integrated circuit, said protection device comprising: a biased diode string (26) operating as a diode clamp to provide noise isolation between said first peripheral supply potential and said first internal supply potential, said biased diode string having an anode coupled to said first peripheral supply potential and its cathode coupled to said first internal supply potential.
Claim 2
Independent Claim
185 words
A device for protecting an integrated circuit having an input/output buffer against electrostatic discharge, said input/output buffer including a first diode (22) having its anode coupled to a pad of said integrated circuit and its cathode coupled to a first peripheral supply potential, a second diode (24) having its anode coupled to an input node of said integrated circuit and its cathode coupled to a first internal supply potential, a third diode (23) having its anode coupled to a second internal supply potential and its cathode coupled to said input node, a fourth diode (25) having its anode coupled to said second internal supply potential and its cathode coupled to a second peripheral supply potential, and a resistance (37) connected between said pad and said input node of said integrated circuit, said protection device comprising: a biased diode string (26) operating as a diode clamp to provide noise isolation between said first peripheral supply potential and said first internal supply potential, said biased diode string having an anode coupled to said first peripheral supply potential and its cathode coupled to said first internal supply potential.
Claim 3
Dependent Claim
49 words
The protection device defined by claim 1 wherein said biased diode string (26) utilizes a set of biasing resistances and a corresponding set of at least two series connected diodes, each biasing resistance coupled in parallel to one of said corresponding sets of at least two series connected diodes.
Claim 4
Dependent Claim
30 words
The protection device defined by claim 2 wherein there is an equipartition of voltage through each said set of at least two series connected diodes in the biased diode string.
Claim 5
Dependent Claim
34 words
The protection device defined by claim 3 wherein the resistance for each set of at least two series connected diodes is defined by the sequence: ##EQU6## starting from the positive end of the string.
Claim 6
Dependent Claim
30 words
The device defined by claim 3 wherein a buffered voltage divider is used to provide equipartition of voltage through each of said sets of at least two series connected diodes.
Claim 7
Dependent Claim
24 words
The device defined by claim 5 wherein the buffered voltage divider operates to supply extra bias current to the middle of said diode chain.
Claim 8
Dependent Claim
31 words
The device defined by claim 5 wherein the buffered voltage divider comprises a leaker pair of transistors and a source follower transistor to supply said extra bias current only when needed.
Claim 9
Dependent Claim
67 words
The protection device defined by claim 1 wherein said biased diode string is tapered so that the p+ finger length of each succeeding stage is less than or equal to the p+ finger length of its preceding stage and so that the p+ finger length of at least one of said stages is less than the p+ finger length of at least one of said preceding stages.
Claim 10
Dependent Claim
31 words
The device defined by claim 8 wherein the p+ finger length of each succeeding stage which has a p+ finger length less than its preceding stages shrinks by a predetermined factor.
Claim 11
Dependent Claim
42 words
The device defined by claim 9 wherein the predetermined factor is determined by device modeling taking into account current dependent PNP β and device resistance for the electrostatic discharge test regime and desired leakage behavior over temperature for the device's operation regime.
Claim 12
Independent Claim
109 words
A device for protecting an integrated circuit having a power supply protected against electrostatic discharge, said power supply including a first diode (22) having its anode coupled to a pad of said integrated circuit and its cathode coupled to a first peripheral supply potential, a second diode (26) having its anode coupled to said first peripheral supply potential and its cathode coupled to a first internal supply potential, said protection device comprising: a cantilevered diode string (30) operating as a power supply electrostatic discharge clamp, said cantilevered diode string having an anode coupled to said first internal supply potential and a cathode coupled to a second internal supply potential.
Claim 13
Independent Claim
109 words
A device for protecting an integrated circuit having a power supply protected against electrostatic discharge, said power supply including a first diode (22) having its anode coupled to a pad of said integrated circuit and its cathode coupled to a first peripheral supply potential, a second diode (26) having its anode coupled to said first peripheral supply potential and its cathode coupled to a first internal supply potential, said protection device comprising: a cantilevered diode string (30) operating as a power supply electrostatic discharge clamp, said cantilevered diode string having an anode coupled to said first internal supply potential and a cathode coupled to a second internal supply potential.
Claim 14
Dependent Claim
20 words
The protection device defined by claim 11 wherein the cantilevered diode string utilizes a capacitor as a power supply anchorage.
Claim 15
Dependent Claim
38 words
The protection device defined by claim 11 wherein said cantilevered diode string (30) utilizes a set of biasing resistances and a corresponding set of series connected diodes, each biasing resistance coupled in parallel to a corresponding diode set.
Claim 16
Dependent Claim
27 words
The protection device defined by claim 13 wherein during steady state, substantially the same voltage is reached in each said diode set in the cantilevered diode string.
Claim 17
Dependent Claim
28 words
The protection device defined by claim 14 wherein the resistance for each diode pair is defined by the sequence: ##EQU7## starting from the positive end of the string.
Claim 18
Dependent Claim
67 words
The protection device defined by claim 11 wherein said cantilevered diode string is tapered so that the p+ finger length of each succeeding stage is less than or equal to the p+ finger length of its preceding stage and so that the p+ finger length of at least one of said stages is less than the p+ finger length of at least one of said preceding stages.
Claim 19
Dependent Claim
21 words
The protection device defined by claim 16 wherein the p+ finger length of each succeeding stage shrinks by a predetermined factor.
Claim 20
Dependent Claim
43 words
The protection device defined by claim 17 wherein the predetermined factor is determined by device modeling taking into account current dependent PNP β and device resistance for the electrostatic discharge test regime and desired leakage behavior over temperature for the device's operation regime.
Claim 21
Dependent Claim
21 words
The protection device defined by claim 11 wherein the cantilevered diode string utilizes a transistor network as a power supply anchorage.
Claim 22
Dependent Claim
14 words
The protection device defined by claim 19 wherein the transistor network comprises n-channel devices.
Claim 23
Dependent Claim
18 words
The protection device defined by claim 19 wherein the transistor network comprises a two stage RC delay circuit.
Claim 24
Dependent Claim
188 words
The protection device defined by claim 19 wherein the transistor network comprises: a) a first p-FET device whose gate is coupled to a capacitance, whose source and drain are coupled between the output end of said cantilevered diode string and Vss; b) a second p-FET device coupled between a node formed by said capacitance and the gate of said first device and, said second p-FET device adapted to provide a resistance so as to provide an RC time constant of at least one microsecond; c) a third p-FET device whose source and drain are coupled between the output end of said cantilevered diode string and Vccx, said third p-FET device adapted to provide a predetermined leakage current to the output end of said cantilevered diode string; d) a n-FET device whose source and drain are coupled between the gates of said second and third p-FET devices and Vss, wherein after said RC induce time delay, said first p-FET device turns off and said second p-FET device operates to assure that the voltage of said capacitance is less than or equal to the voltage input to said diode string.
Claim 25
Dependent Claim
17 words
The protection device defined by claim 22 wherein the capacitance comprises at least two series connected capacitors.
References Cited (Backward Citations)
US3573550A
Cited
US3943427A
Cited
US4585905A
Cited
EP0296675A2
Cited
GB2234126A
Cited
US5311391A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-06-25 | 1999-12-25 | 2000-06-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-06-25 | 2003-12-25 | 2004-06-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-06-25 | 2007-12-25 | 2008-06-25 | $7700.00 | Window Closed / Lapsed |