Voltage regulator circuit for a switching circuit load
A voltage regulator receives a reference voltage and generates a regulated voltage using a MOSFET having a gate terminal configured to receive a control voltage. A charge pump receives the regulated voltage and generates a charge pump voltage in response to an enable signal and a clock signal generated in response to the enable signal. The voltage regulator further includes a first switched capacitor circuit coupled to the gate terminal and configured to selectively charge a first capacitor with a first current and impose a first voltage drop on the control voltage in response to assertion of the enable signal. The voltage regulator also includes a second switched capacitor circuit coupled to the gate terminal and configured to selectively charge a second capacitor with a second current and impose a second voltage drop on the control voltage in response to one logic state of the clock signal.
1. A circuit, comprising:
a voltage regulator circuit configured to receive a reference voltage and generate a regulated output voltage, said voltage regulator circuit including a field effect transistor (FET) device having a gate terminal configured to receive a control voltage and a drain terminal configured to source an output current for generating the regulated output voltage; and
a charge pump circuit having an input configured to receive the regulated output voltage, an output configured to generate a pumped voltage, and a clock input configured to receive a clock signal, wherein pumping operation of said charge pump circuit is driven by opposite first and second logic states of the clock signal;
wherein said voltage regulator circuit further includes a switched capacitor circuit coupled to the gate terminal and configured to selectively charge a capacitor with a charging current sunk from the gate terminal of the FET device in response to the first logic state of the clock signal and selectively discharge the capacitor in response to the second logic state of the clock signal.
2. The circuit of claim 1 , wherein the charge pump circuit comprises a multi-stage capacitor circuit.
3. The circuit of claim 2 , wherein a stage of the multi-stage capacitor circuit is implemented as a Dickson circuit.
4. The circuit of claim 2 , wherein a stage of the multi-stage capacitor circuit is implemented as a voltage doubler circuit.
5. The circuit of claim 1 , wherein the switched capacitor circuit further comprises a voltage limiting circuit coupled in series with the capacitor between the gate terminal and a ground.
6. The circuit of claim 5 , wherein the voltage limiting circuit comprises a FET device having a gate terminal biased by a bias voltage.
7. The circuit of claim 1 , wherein the voltage regulator circuit is a low drop out (LDO) type circuit.
8. The circuit of claim 1 , wherein the switched capacitor circuit further comprises:
a first transistor switch coupled in series with the capacitor between in the gate terminal of the MOSFET device and ground, said first transistor switch actuated to a closed state in response to the first logic state of the clock signal and actuated to an open state in response to the second logic state of the clock signal; and
a second transistor switch coupled in parallel with the capacitor, said second transistor switch actuated to an open state in response to the first logic state of the clock signal and actuated to a closed state in response to the second logic state of the clock signal.