Patent US5287022A successfully refreshed from Google Patents.
US5287022A
Expired / Lapsed
US
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Method and circuit for controlling voltage reflections on transmission lines
Assignee: Credence Systems Corp
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Filing: 1993-03-24
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Granted: 1994-02-15
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Expires: 2013-03-24
Abstract
Abstract The invention is a termination circuit which may be used to terminate a tester end of a transmission line between the tester and a digital device under test (DUT). The termination circuit is a clamp circuit which acts as a non-linear resistor of infinite resistance for termination voltages between zero volts (or low logic level voltage) and the power supply voltage V cc (or high logic level voltage) of the DUT, and which provides a substantially constant slope resistance set to equal the characteristic impedance (Z O ) of the transmission line for voltages outside this range. Given that the output impedance of the DUT is less than the characteristic impedance Z O of a transmission line, and given the characteristics of the clamp circuit, all reflections on the transmission line as a result of unmatched impedances are totally eliminated by the clamp in twice the delay time of the transmission line. After the reflections are eliminated, the clamp acts as an open circuit. This clamp circuit may be used in virtually any application where reflections are a concern.
Inventors
- 👤 Kenneth R. Wilsher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 15:03
CPC Classifications
H; H04; H04L; H04L25/00; H04L25/02; H04L25/0264; H04L25/0298; G; G01; G01R; G01R31/00; G01R31/28; G01R31/317; G01R31/3181; G01R31/319; G01R31/31917; G01R31/31924; H03; H03K; H03K5/00; H03K5/01; H03K5/08
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
277 words
A circuit comprising; a transmission line having a first end for being connected to an output of an electrical device which is switchable between a low output state and a high output state, said electrical device having an output impedance approximately equal to or below a characteristic impedance of said transmission line, said electrical device outputting a first voltage level in said low output state and outputting an second voltage level in said high output state when connected to said transmission line; a non-linear load circuit having an input terminal connected to a second end of said transmission line, said non-linear load circuit providing a substantially open circuit to said input terminal when a voltage at said input terminal is between said first voltage level and said second voltage level, said non-linear load circuit also providing a substantially constant first load resistance between said input terminal and a reference voltage terminal only when a voltage at said input terminal is below said first voltage level or above said second voltage level, wherein said first load resistance is approximately equal to said characteristic impedance of said transmission line, and wherein when said electrical device connected to said first end of said transmission line switches from said low output state to said high output state, a first positive forward voltage step is propagated on said transmission line toward said second end of said transmission line such that on arriving at said second end of said transmission line with non-linear load circuit provides a first positive reflected voltage on said transmission line of approximately fifty per cent of a difference between said second voltage level and said first voltage level.
Claim 2
Dependent Claim
277 words
A circuit comprising; a transmission line having a first end for being connected to an output of an electrical device which is switchable between a low output state and a high output state, said electrical device having an output impedance approximately equal to or below a characteristic impedance of said transmission line, said electrical device outputting a first voltage level in said low output state and outputting an second voltage level in said high output state when connected to said transmission line; a non-linear load circuit having an input terminal connected to a second end of said transmission line, said non-linear load circuit providing a substantially open circuit to said input terminal when a voltage at said input terminal is between said first voltage level and said second voltage level, said non-linear load circuit also providing a substantially constant first load resistance between said input terminal and a reference voltage terminal only when a voltage at said input terminal is below said first voltage level or above said second voltage level, wherein said first load resistance is approximately equal to said characteristic impedance of said transmission line, and wherein when said electrical device connected to said first end of said transmission line switches from said low output state to said high output state, a first positive forward voltage step is propagated on said transmission line toward said second end of said transmission line such that on arriving at said second end of said transmission line with non-linear load circuit provides a first positive reflected voltage on said transmission line of approximately fifty per cent of a difference between said second voltage level and said first voltage level.
Claim 3
Dependent Claim
13 words
The circuit of claim 1 wherein said electrical device is a CMOS device.
Claim 4
Dependent Claim
115 words
The circuit of claim 1 wherein said non-linear load circuit comprises: a first linear load having a first end connected to said input terminal; a first diode means having an anode connected to a second end of said first linear load and having a cathode connected to a first voltage source for providing a voltage to said cathode which is approximately one diode drop below said second voltage level; and a second diode means having a cathode connected to said second end of said first linear load and having an anode connected to a second voltage source for providing a voltage to said anode which is approximately one diode drop above said first voltage level.
Claim 5
Dependent Claim
13 words
The circuit of claim 3 wherein said first linear load comprises a resistor.
Claim 6
Dependent Claim
118 words
The circuit of claim 3 wherein said first voltage source comprises: a third diode means having a cathode connected to said cathode of said first diode means and having an anode connected to a third voltage source for providing a voltage to said anode equal to said second voltage level; and wherein said second voltage source comprises: a fourth diode means having an anode connected to said anode of said second diode means and having a cathode connected to a fourth voltage source for providing a voltage to said cathode equal to said first voltage level; and a second linear load connected between said cathode of said third diode means and said anode of said fourth diode means.
Claim 7
Dependent Claim
132 words
The circuit of claim 1 wherein said non-linear load circuit comprises: a first diode means having an anode connected to said input terminal and having a cathode connected to a first terminal of a first linear load, a second terminal of said first linear load being connected to a first voltage source for providing a voltage to said second terminal which is approximately one diode drop below said second voltage level; and a second diode means having a cathode connected to said input terminal and having an anode connected to a first terminal of a second linear load, a second terminal of said second linear load being connected to a second voltage source for providing a voltage to said second terminal which is approximately one diode drop above said first voltage level.
Claim 8
Dependent Claim
14 words
The circuit of claim 6 wherein said first and second linear loads are resistors.
Claim 9
Dependent Claim
128 words
The circuit of claim 1 wherein said non-linear load circuit comprises: a first linear load having a first end connected to said input terminal; a first diode means having an anode connected to a second end of said first linear load and having a cathode connected to a first voltage source for providing a voltage to said cathode which is approximately one diode drop below said second voltage level; a second linear load having a first end connected to said input terminal; and a second diode means having a cathode connected to a second end of said second linear load and having an anode connected to a second voltage source for providing a voltage to said anode which is approximately one diode drop above said first voltage level.
Claim 10
Dependent Claim
118 words
The circuit of claim 8 wherein said first voltage source comprises: a third diode means having a cathode connected to said cathode of said first diode means and having an anode connected to a third voltage source for providing a voltage to said anode equal to said second voltage level; and wherein sad second voltage source comprises: a fourth diode means having an anode connected to said anode of said second diode means and having a cathode connected to a fourth voltage source for providing a voltage to said cathode equal to said first voltage level; and a third linear load connected between said cathode of said third diode means and said anode of sad fourth diode means.
Claim 11
Dependent Claim
204 words
The circuit of claim 3 further comprising: a third diode means having a cathode connected to said cathode of said first diode means and having an anode connected to a third voltage source for providing a bias voltage to said anode; a fourth diode means having an anode connected to said anode of said second diode means and having a cathode connected to said anode of said third diode means; a first current source coupled to said anode of said second diode means; and a second current source coupled to said cathode of said first diode means, and said first voltage source comprises: a fifth diode means having an anode connected to said cathode of said first diode means, a cathode of said third diode means connected to a fourth voltage source for providing a voltage to said cathode which is approximately two diode drops below said second voltage level; and wherein said second voltage source comprises: a sixth diode means having a cathode connected to said anode of said second diode means, an anode of said sixth diode mean connected to a fifth voltage source for providing a voltage to said anode which is approximately two diode drops above said first voltage level
Claim 12
Dependent Claim
30 words
The circuit of claim 10 further comprising a second linear load connected between said third voltage source for providing said bias voltage and said anode of said fifth diode means.
Claim 13
Dependent Claim
20 words
The circuit of claim 11 wherein said first current source generates a substantially same current as said second current source.
Claim 14
Dependent Claim
95 words
The circuit of claim 1 wherein when said electrical device connected to said first end of said transmission line switches from said high output state to said low output state, a first negative forward voltage step is propagated on said transmission line toward said second end of said transmission line such that on arriving at said second end of said transmission line said non-linear load circuit provides a first negative reflected voltage on said transmission line of approximately fifty per cent of a difference between that said first voltage level and said second voltage level.
References Cited (Backward Citations)
US2867735A
Cited
US2927223A
Cited
US3214680A
Cited
US3287567A
Cited
US3568073A
Cited
US3805090A
Cited
US4153848A
Cited
US4345171A
Cited
US4543495A
Cited
US4661979A
Cited
US4952795A
Cited
US5029284A
Cited
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