Ring oscillator with NMOS or PMOS variation insensitivity
First Claim
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1. A method of setting a body bias potential, comprising the step of:
- determining the frequency of a first ring oscillator by probing an output pad coupled to the ring oscillator;
setting a first predetermined body bias potential for a first conductivity type insulated gate field effect transistor (IGFET) in response to the frequency of the first ring oscillator by programming a first programmable voltage generator that provides the first predetermined body biased potential based on a first programming state; and
providing a supply voltage to the ring oscillator of less than 1.0 volt.
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Abstract
A low voltage ring oscillator circuit can have a frequency variation that depends on process variations of insulated gate field effect transistors (IGFETs) of a first conductivity type without substantially being affected by process variations to IGFETs of a second conductivity type. A ring oscillator stage may include an inverter including only IGFETs of the first conductivity type. The inverter may be coupled to a boot circuit that boosts the gate potential of a first IGFET of the first conductivity type with a timing such that IGFETs of the second conductivity type in the boot circuit do not affect the frequency variations of the ring oscillator circuit.
267 Citations
17 Claims
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1. A method of setting a body bias potential, comprising the step of:
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determining the frequency of a first ring oscillator by probing an output pad coupled to the ring oscillator; setting a first predetermined body bias potential for a first conductivity type insulated gate field effect transistor (IGFET) in response to the frequency of the first ring oscillator by programming a first programmable voltage generator that provides the first predetermined body biased potential based on a first programming state; and providing a supply voltage to the ring oscillator of less than 1.0 volt. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A ring oscillator circuit including a plurality of ring oscillator stages, at least one ring oscillator stage comprising:
an inverter circuit coupled to receive an output from a first previous output terminal of a first previous ring oscillator stage at an input terminal and provide an output at an output terminal coupled to a subsequent input terminal of a subsequent ring oscillator stage, the inverter circuit including a first insulated gate field effect transistor (IGFET) having a first conductivity type, the first IGFET having a source terminal coupled to a first potential, a drain terminal coupled to the output terminal, and a gate terminal coupled to the input terminal; and a second IGFET of the first conductivity type having a source terminal coupled to the output terminal, a drain terminal coupled to a second potential, and a gate terminal coupled to a boot node, the boot node receives a boosted potential outside the bounds of the first potential and the second potential. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
Specification