Level shifting circuit
AssigneePacesetter, Inc.
InventorRichard C. Kimoto
Life of this patent
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Abstract
A level shifter shifts the level of an input signal from a second voltage domain to a first voltage domain. To accommodate different input signal levels (e.g., including sub-threshold input signal levels) that may arise due to changes in the supply voltage for the second voltage domain, current for a latch circuit of the level shifter is limited based on the supply voltage for the second voltage domain. In this way, a drive circuit of the level shifter that controls the latch circuit based on the input signal is able to initiate a change of state of the latch circuit over a wide range of input signal levels.
Claims19
A level shifting apparatus, comprising:
- a latch circuit configured to provide an output signal for a first voltage domain;
- a drive circuit configured to provide signals for controlling the latch circuit based on an input signal from a second voltage domain;
- and
- a current limiting circuit configured to limit current sourced to the latch circuit based on a supply voltage for the second voltage domain.
A method of level shifting, comprising:
- limiting current sourced to a circuit, wherein the current is limited based on a supply voltage for a second voltage domain;
- receiving an input signal from the second voltage domain;
- and
- controlling an output signal of the circuit based on the input signal, wherein the output signal is provided for a first voltage domain.
A level shifter, comprising:
- a cross-coupled transistor pair configured to provide an output signal for a first voltage domain;
- a first transistor pair configured to provide signals for controlling the cross-coupled transistor pair based on an input signal from a second voltage domain, wherein the cross-coupled transistor pair is coupled to a circuit ground via the first transistor pair;
- and
- a current mirror circuit comprising a second transistor pair and configured to limit current sourced to the cross-coupled transistor pair based on a supply voltage for the second voltage domain, wherein the cross-coupled transistor pair is coupled to a supply voltage for the first voltage domain via the second transistor pair.
Dependencies are inferred from the claim text.