VBB reference for pumped substrates
First Claim
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1. A circuit implemented on a substrate having a voltage generated by a charge pump, said circuit comprising:
- a current source providing a first current that is proportional to temperature; and
a level shifter coupled to said current source and said substrate, said level shifter providinga first voltage that is shifted from said voltage of said substrate, wherein said level shifter comprises;
a first P-channel transistor coupled to said current source, said first P-channel transistor conducting a current substantially equal to said first current;
a first resistive device coupled to a drain of said first P-channel transistor; and
a first PNP transistor having a base and collector coupled to said substrate and an emitter coupled to said first resistive device.
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Abstract
An embodiment of a pumped substrate system includes an oscillator, capacitive pump, comparing circuit, and a level shifter. The level shifter is coupled between the substrate and the positive input lead of the comparator and shifts the voltage level present on the substrate by a voltage Vbg. The comparator compares ground potential to the shifted substrate voltage. The oscillator, capacitive pump and comparing circuit form a negative feedback loop which operates to maintain the substrate voltage substantially equal to -Vbg. In one embodiment, the level shifter includes a band gap reference.
94 Citations
19 Claims
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1. A circuit implemented on a substrate having a voltage generated by a charge pump, said circuit comprising:
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a current source providing a first current that is proportional to temperature; and a level shifter coupled to said current source and said substrate, said level shifter providing a first voltage that is shifted from said voltage of said substrate, wherein said level shifter comprises; a first P-channel transistor coupled to said current source, said first P-channel transistor conducting a current substantially equal to said first current; a first resistive device coupled to a drain of said first P-channel transistor; and a first PNP transistor having a base and collector coupled to said substrate and an emitter coupled to said first resistive device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for maintaining a voltage of a substrate at a predetermined level, said method comprising the steps of:
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providing a first voltage that is substantially equal to a sum of a base-to-emitter voltage of a transistor and a product of a thermal voltage and a constant, wherein said constant is a product of a ratio of resistances and a natural logarithm of a ratio of emitter areas; applying said first voltage between said substrate and a first node; and varying a charge in said substrate to maintain a voltage of said first node at a second voltage, wherein the voltage of said substrate is maintained at said predetermined level. - View Dependent Claims (10, 11)
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12. A structure for maintaining a voltage of a substrate at a predetermined level, said structure comprising:
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means for providing and applying a first voltage that is substantially equal to a sum of a base-emitter voltage of a transistor and a product of a thermal voltage and a constant, wherein said constant is a product of a ratio of resistances and a natural logarithm of a ratio of emitter areas; said first voltage being applied between said substrate and a first node; and means for varying a charge in said substrate to maintain a voltage of said first node at a second voltage, wherein the voltage of said substrate is maintained at said predetermined level. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A system for maintaining a voltage of a substrate at a predetermined voltage, said system comprising:
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an oscillator; a gating circuit having an input lead coupled to an output lead of said oscillator; a pump circuit having an input lead coupled to an output lead of said gating circuit and an output lead coupled to said substrate; a level shifter coupled between said substrate and a node; and a comparing circuit having a first input lead coupled to said node, a second input lead coupled to a voltage source and an output lead coupled to a control lead of said gating circuit; wherein said oscillator is a voltage-controlled oscillator and said comparing circuit is an amplifier, said voltage-controlled oscillator having an input lead coupled to an output lead of said amplifier.
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Specification