PMOS-output LDO with full spectrum PSR
AssigneeQUALCOMM Incorporated
InventorSoheil Golara
Life of this patent
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Abstract
A PMOS-output LDO with full spectrum PSR is disclosed. In one implementation, a LDO includes a pass transistor (MO) having a source coupled to an input voltage (Vin); a noise cancelling transistor (MD) having a source coupled to the Vin, a gate coupled to a drain and a gate of the pass transistor; a source follower transistor (MSF) having a source coupled to a drain of the pass transistor, a drain coupled to the drain and gate of the noise cancelling transistor; a current sink coupled between the drain of the source follower transistor and ground; and an error amplifier having an output to drive the gate of the source follower transistor.
Claims16
A low dropout (LDO) regulator circuit, comprising:
- a pass transistor (MO) having a source, a drain, and a gate, the source coupled to an input voltage (Vin);
- a noise cancelling transistor (MD) having a source, a drain, and a gate, the source coupled to the Vin, the gate coupled to the drain of the noise cancelling transistor and the gate of the pass transistor;
- a source follower transistor (MSF) having a source, a drain, and a gate, the source coupled to the drain of the pass transistor, the drain coupled to the drain and the gate of the noise cancelling transistor;
- a current sink coupled between the drain of the source follower transistor and ground;
- an error amplifier having an output, a positive input terminal, and a negative input terminal, the output coupled to the gate of the source follower transistor, the positive input terminal configured to receive a reference voltage (Vref);
- and
- a feedback resistor coupled between the drain of the pass transistor and the negative input terminal of the error amplifier.
A method to provide a regulated low voltage from an input voltage (Vin), the method comprising:
- receiving the input voltage at a source of a pass transistor (MO);
- coupling a source of a noise cancelling transistor (MD) to the source of the pass transistor, wherein the noise cancelling transistor is configured into a diode;
- coupling a source of a source follower transistor (MSF) to a drain of the pass transistor, and coupling a drain of the source follower transistor to a drain and a gate of the noise cancelling transistor;
- coupling a current sink between the drain of the source follower transistor and ground;
- receiving a reference voltage (Vref) at a positive input terminal of an error amplifier;
- coupling a feedback resistor between the drain of the pass transistor and a negative input terminal of the error amplifier to provide a feedback voltage to the error amplifier;
- generating an output of the error amplifier based on the feedback voltage and the reference voltage;
- and
- driving a gate of the source follower transistor with the output of the error amplifier.
Dependencies are inferred from the claim text.