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US 7,405,546 B2Granted
Standard CMOS low-noise high PSRR low drop-out regulator with new dynamic compensation
AssigneeAtmel Corporation
InventorsHafid Amrani, Hubert Cordonnier, Xavier Rabeyrin
Life of this patent
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Abstract
A voltage regulator circuit has a first amplifier stage with input and output terminals, a feedback terminal, a pole-inducing transistor, and a compensating network coupled to the output terminal. A second amplifier stage has an input coupled to the first amplifier output, first and second current mirrors, and a pass transistor.
Claims17
A voltage regulator circuit comprising:
- a first amplifier stage having a first amplifier input terminal, a first amplifier output terminal, a feedback terminal, a pole-inducing transistor, and a compensation network coupled to the output terminal, the compensation network having a compensating capacitor and compensating transistor;
- a second amplifier stage having a second amplifier input terminal coupled to the first amplifier output terminal, a first current mirror, a second current mirror, and a pass transistor coupling a first power supply potential to an output terminal, the first current mirror conducting a fraction of a load current supplied by the pass transistor, and the second current mirror conducting a fraction of the current supplied by the first current mirror;
- a conduction path coupling the compensating transistor to the first current mirror;
- and
- a conduction path coupling the pole-inducing transistor to the second current mirror.
2 more elements
A method of frequency compensating a voltage regulator circuit, the voltage regulator circuit having a first stage amplifier and a second stage amplifier, the method comprising:
- varying a unity gain frequency of an open-loop system transfer function of the regulator circuit such that the unity gain frequency increases in approximate proportion to the square root of a load current supplied by the voltage regulator circuit;
- introducing a pole-zero doublet at an output of the first stage amplifier such that the frequency associated with the pole-zero doublet increases in approximate proportion to the square root of the load current, and such that a splitting ratio of the pole-zero doublet is substantially invariant with the load current;
- and
- introducing a second pole into an open-loop transfer function of the first stage amplifier, such that the second pole frequency is approximately proportional to the load current.
1 more element
A method of frequency compensating a voltage regulator circuit, the voltage regulator circuit having a first stage amplifier and a second stage amplifier, the method comprising:
- p1 varying a unity gain frequency of an open-loop system transfer function of the regulator circuit such that the unity gain frequency increases in direct proportion to a frequency associated with a pole-zero doublet introduced at an output of the first stage amplifier;
- and
- maintaining a splitting ratio of the pole-zero doublet such that the splitting ratio is substantially invariant with a load current supplied by the voltage regulator current.
A low drop-out (LDO) voltage regulator circuit comprising:
- a first amplifier means for accepting an input voltage and a feedback voltage, the first amplifier means providing a first amplifier output signal;
- a second amplifier means coupled to the first amplifier means and accepting the first amplifier output signal, the second amplifier means providing coupling between a first power supply potential and an output terminal;
- a zero compensation means for introducing a pole-zero doublet at the first amplifier output signal, the pole-zero doublet having a frequency increasing in approximate proportion to the square root of a load current supplied by the regulator circuit, the pole-zero doublet further having a splitting ratio essentially invariant with the load current;
- a second pole introduction means for introducing a second pole into an open-loop transfer function of the first amplifier means, a frequency of the second pole increasing in approximate proportion to the load current;
- and
- a unity gain control means for increasing a unity gain frequency of an open-loop transfer function of the regulator circuit in approximate proportion to the square root of the load current.
3 more elements
A voltage regulator circuit comprising:
- a first amplifier stage having a first amplifier input terminal, a first amplifier output terminal, a feedback terminal, a pole-inducing transistor, and a compensation network coupled to the output terminal, the compensation network having a compensating capacitor and compensating transistor;
- a second amplifier stage having a second amplifier input terminal coupled to the first amplifier output terminal, a first current mirror, a second current mirror, and a pass transistor configured to couple a first power supply potential to an output terminal, the first current mirror configured to conduct a fraction of a load current supplied by the pass transistor, and the second current mirror configured to conduct a fraction of the current supplied by the first current mirror;
- a conduction path coupling the compensating transistor to the first current mirror;
- and
- a conduction path coupling the pole-inducing transistor to the second current mirror.
2 more elements
Dependencies are inferred from the claim text.