LDO and load switch supporting a wide range of load capacitance
First Claim
1. A low drop-out (LDO) load switch linear voltage regulator (LVR) circuit having an open loop transfer function, comprising:
- a feedback network comprising;
a first input coupled to an output of the LVR circuit;
a second input coupled to a reference voltage; and
an output; and
a pass transistor comprising;
a gate terminal driven by the output of the feedback network;
a first terminal coupled to an input of the LVR circuit; and
a second terminal coupled to the output of the LVR circuit,wherein the feedback network further comprises an output scaling network, an error amplifier, a first buffer, a second buffer, a capacitor, and a zero generation circuit that is connected to the first buffer and the second buffer, and is configured to generate a zero,wherein the first buffer comprises;
an input coupled to an output of the error amplifier and an input of the second buffer; and
an output coupled to a first terminal of the capacitor,wherein the error amplifier comprises;
a first input for receiving the reference voltage; and
a second input coupled to an output of the output scaling network,wherein the capacitor comprises;
the first terminal connected to the output of the first buffer; and
a second terminal connected to the output of the LVR,wherein the second buffer comprises an output driving the gate terminal of the pass transistor, andwherein the output scaling network comprises;
an input connected to the output of the LVR; and
the output connected to the second input of the error amplifier, wherein the output scaling network is configured to scale down an output voltage level of the LVR, using a resistive divider, andwherein the input of the first buffer is coupled to the output of the error amplifier and the input of the second buffer via the zero generation circuit.
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Accused Products
Abstract
An architecture and method to maintain stability of a low drop-out (LDO)/load switch linear voltage regulator (LVR). The architecture method support optionally determining during a power-up phase and by using a load detection circuit, the estimated load parameters that represents at least one selected from a group consisting of: the load time constant and the load resistor at an output node of the LDO/load switch LVR, and adjusting, based on the estimated output load parameters, an adaptive RC network in the LDO/load switch LVR, wherein the adaptive RC network produces an adaptive zero in a feedback network transfer function of the LDO/load switch LVR, wherein the adaptive zero reduces an effect of a non-dominant pole in the open loop transfer function of the LDO/load switch LVR, and wherein a frequency of the adaptive zero is adjusted based on the estimated load parameters.
17 Citations
19 Claims
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1. A low drop-out (LDO) load switch linear voltage regulator (LVR) circuit having an open loop transfer function, comprising:
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a feedback network comprising;
a first input coupled to an output of the LVR circuit;
a second input coupled to a reference voltage; and
an output; anda pass transistor comprising;
a gate terminal driven by the output of the feedback network;
a first terminal coupled to an input of the LVR circuit; and
a second terminal coupled to the output of the LVR circuit,wherein the feedback network further comprises an output scaling network, an error amplifier, a first buffer, a second buffer, a capacitor, and a zero generation circuit that is connected to the first buffer and the second buffer, and is configured to generate a zero, wherein the first buffer comprises; an input coupled to an output of the error amplifier and an input of the second buffer; and an output coupled to a first terminal of the capacitor, wherein the error amplifier comprises; a first input for receiving the reference voltage; and a second input coupled to an output of the output scaling network, wherein the capacitor comprises; the first terminal connected to the output of the first buffer; and a second terminal connected to the output of the LVR, wherein the second buffer comprises an output driving the gate terminal of the pass transistor, and wherein the output scaling network comprises; an input connected to the output of the LVR; and the output connected to the second input of the error amplifier, wherein the output scaling network is configured to scale down an output voltage level of the LVR, using a resistive divider, and wherein the input of the first buffer is coupled to the output of the error amplifier and the input of the second buffer via the zero generation circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A low drop-out (LDO) load switch linear voltage regulator (LVR) circuit having an open loop transfer function, comprising:
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a feedback network comprising;
a first input coupled to an output of the LVR circuit;
a second input coupled to a reference voltage; and
an output; anda pass transistor comprising;
a gate terminal driven by the output of the feedback network;
a first terminal coupled to an input of the LVR circuit; and
a second terminal coupled to the output of the LVR circuit,wherein the feedback network further comprises an output scaling network, an error amplifier, a first buffer, a second buffer, a capacitor, and a zero generation circuit that is connected to the first buffer and the second buffer, and is configured to generate a zero, wherein the LVR circuit further comprises a load detection circuit comprising; an input coupled to the output of the LVR circuit; and an output coupled to the feedback network, and wherein the load detection circuit comprises; a current source comprising; a first terminal coupled to the output of the LVR circuit; and a second terminal coupled to a fixed potential node; an amplifier comprising; a first input coupled to the output of the LVR circuit; and a second input coupled to a constant voltage; and a decision circuit configured to generate a count proportional to a time period for the current source to charge the load parameter for the output of the LVR circuit to reach the constant voltage.
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14. A low drop-out (LDO) load switch linear voltage regulator (LVR) circuit having an open loop transfer function, comprising:
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a feedback network comprising;
a first input coupled to an output of the LVR circuit;
a second input coupled to a reference voltage; and
an output; anda pass transistor comprising;
a gate terminal driven by the output of the feedback network;
a first terminal coupled to an input of the LVR circuit; and
a second terminal coupled to the output of the LVR circuit,wherein the feedback network further comprises an output scaling network, an error amplifier, a first buffer, a second buffer, a capacitor, and a zero generation circuit that is connected to the first buffer and the second buffer, and is configured to generate a zero, and wherein the LVR circuit further comprises a load detection circuit comprising; an input coupled to the output of the LVR circuit; and an output coupled to the feedback network, and wherein the LVR circuit further comprises a chip controller configured to; activate the load detection circuit block during a power up phase of the LVR circuit; and de-activate the load detection circuit block subsequent to the power up phase of the LVR circuit. - View Dependent Claims (15)
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16. A low drop-out (LDO) load switch linear voltage regulator (LVR) circuit having an open loop transfer function, comprising:
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a feedback network comprising;
a first input coupled to an output of the LVR circuit;
a second input coupled to a reference voltage; and
an output; anda pass transistor comprising;
a gate terminal driven by the output of the feedback network;
a first terminal coupled to an input of the LVR circuit; and
a second terminal coupled to the output of the LVR circuit,wherein the feedback network further comprises an output scaling network, an error amplifier, a first buffer, a second buffer, a capacitor, and a zero generation circuit that is connected to the first buffer and the second buffer, and is configured to generate a zero, and wherein the LVR circuit further comprises a load detection circuit comprising; an input coupled to the output of the LVR circuit; and an output coupled to the feedback network, and wherein the load detection circuit is configured to output a count representing an estimated load parameter that indicates if there is a short circuit at the output node of the LVR.
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17. A method for adjusting stability of a low drop-out (LDO)/load switch linear voltage regulator (LVR) having an open loop transfer function, comprising:
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determining, during a power-up phase and by a load detection circuit, an estimated output load parameter that represents at least one selected from a group consisting of;
a load time constant and a load resistor value at an output node of the LDO/load switch LVR; andadjusting, based on the estimated output load parameter, an adaptive RC network in the LDO/load switch LVR, wherein the adaptive RC network produces an adaptive zero in a feedback network transfer function of the LDO/load switch LVR, and wherein the adaptive zero reduces an effect of a non-dominant pole in the open loop transfer function of the LDO/load switch LVR wherein the method further comprises; estimating the output load parameter that represents at least one selected from a group consisting of;
the load time constant and the load resistor value while the LDO/load switch LVR is in an off-state or while the LDO/load switch LVR is in a power-up state,wherein the LDO/load switch LVR remains stable over a plurality of capacitive load conditions ranging from no capacitive load to a 10 .mu.f load, wherein the method further comprises; adjusting the adaptive RC network while estimating the output load parameters; and wherein the adjusting the adaptive RC network involves selecting a frequency of the adaptive zero to reduce phase margin degradation due to the non-dominant pole of the open loop transfer function of the LDO/load switch LVR.
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18. A load detection circuit for a low drop-out (LDO) load switch linear voltage regulator (LVR) with a start-up behavior, comprising:
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a measurement circuit for generating a value representing at least one selected from a group consisting of;
a time constant of an output voltage, a load resistor, and a load capacitor connected to an output of the LDO load switch LVR before start-up; anda control circuit that optimizes, based on the value, the start-up behavior by controlling an output current of the voltage regulator, wherein the control circuit includes an adaptive RC network that produces an adaptive zero in a feedback network transfer function of the LDO/load switch LVR, and wherein the load detection circuit further comprises; a charging circuit coupled to an output node of the LDO load switch LVR and configured to charge the output node; a variable gain amplifier (VGA) coupled to the output node and configured to detect an output voltage level, and a decision circuit coupled to an output of the variable gain amplifier (VGA) and configured to generate outputs that are proportional to load parameters. - View Dependent Claims (19)
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Specification