Low-dropout voltage regulator with level limiter limiting level of output voltage when level of load current changes and method of operating the same
First Claim
1. A low-dropout (LDO) voltage regulator comprising:
- an error amplifier which compares a reference voltage with a feedback voltage of an output voltage and outputs an error signal based on the result of the comparison, the error amplifier being biased by an input voltage;
a first MOS transistor having a gate electrically connected to the error signal, a source electrically connected to the input voltage and a drain electrically connected to the output voltage;
a voltage divider which transmits a predetermined part of the output voltage to the error amplifier as feedback voltage; and
a level limiter which limits a level of the output voltage from changing beyond and below an offset voltage when a level of a load current changes,wherein the level limiter comprises;
a decrease limiter which limits the output voltage from decreasing below a low point of the offset voltage when the load current increases; and
an increase limiter which limits the output voltage from increasing beyond a high point of the offset voltage when the load current decreases.
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Abstract
A low-dropout (LDO) voltage regulator that includes an error amplifier which compares a reference voltage with a feedback voltage of an output voltage and outputs an error signal based on the result of the comparison, the error amplifier being biased by an input voltage; a first MOS transistor having a gate electrically connected to the error signal, a source electrically connected to the input voltage and a drain electrically connected to the output voltage; a voltage divider which transmits a predetermined part of the output voltage to the error amplifier as feedback voltage; and a level limiter which limits a level of the output voltage from changing beyond and below an offset voltage when a level of a load current changes. In accordance with embodiments, A predetermined number of comparators and MOS transistor type-switches are provided to enhance the slew ratio of the regulated output voltage and to reduce standby electricity consumption.
31 Citations
18 Claims
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1. A low-dropout (LDO) voltage regulator comprising:
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an error amplifier which compares a reference voltage with a feedback voltage of an output voltage and outputs an error signal based on the result of the comparison, the error amplifier being biased by an input voltage; a first MOS transistor having a gate electrically connected to the error signal, a source electrically connected to the input voltage and a drain electrically connected to the output voltage; a voltage divider which transmits a predetermined part of the output voltage to the error amplifier as feedback voltage; and a level limiter which limits a level of the output voltage from changing beyond and below an offset voltage when a level of a load current changes, wherein the level limiter comprises; a decrease limiter which limits the output voltage from decreasing below a low point of the offset voltage when the load current increases; and an increase limiter which limits the output voltage from increasing beyond a high point of the offset voltage when the load current decreases. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A low-dropout (LDO) voltage regulator comprising:
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an error amplifier comprising a plurality of transistors which compares a reference voltage with a feedback voltage of an output voltage and outputs an error signal based on the result of the comparison, the error amplifier being biased by an input voltage; a first MOS transistor having a gate electrically connected to the error signal, a source electrically connected to the input voltage and a drain electrically connected to the output voltage; a voltage divider which transmits a predetermined part of the output voltage to the error amplifier as feedback voltage, the voltage divider including a first resistance and a second resistance electrically connected in series between the output voltage and the ground; and a level limiter which limits a level of the output voltage from changing beyond and below an offset voltage when a level of a load current changes, wherein the level limiter comprises; a decrease limiter which limits the output voltage from decreasing below a low point of the offset voltage when the load current increases; and an increase limiter which limits the output voltage from increasing beyond a high point of the offset voltage when the load current decreases. - View Dependent Claims (17)
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18. A method of operating a LDO voltage regulator comprising:
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synthesizing a reference voltage and an offset voltage; and
thenlimiting a level of an output voltage from changing beyond and below the offset voltage when a level of a load current changes by comparing a feed-backed part of an output voltage and the result of the synthesizing, wherein limiting the level of the output voltage comprises; limiting the output voltage from decreasing below a low point of the offset voltage when the load current increases; and limiting the output voltage from increasing beyond a high point of the offset voltage when the load current decreases.
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Specification