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 voltage generator circuit, comprising:
a voltage regulator circuit configured to receive a reference voltage and generate a regulated output voltage, said voltage regulator circuit including a metal oxide field effect transistor (MOSFET) 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 configured to receive the regulated output voltage and generate a charge pump output voltage, said charge pump circuit controlled for operation by an enable signal and a clock signal, wherein the clock signal is generated in response to the enable signal;
wherein said voltage regulator circuit includes:
a first switched capacitor circuit coupled to the gate terminal and configured to selectively charge a first capacitor with a first current sunk from the gate terminal and impose a first decrease of the control voltage in response to assertion of the enable signal; and
a second switched capacitor circuit coupled to the gate terminal and configured to selectively charge a second capacitor with a second current sunk from the gate terminal and impose a second decrease of the control voltage in response to one logic state of the clock signal.
2. The circuit of claim 1 , wherein an oscillator circuit of the charge pump circuit responds to assertion of the enable signal by causing oscillation of the clock signal.
3. The circuit of claim 1 , wherein the first switched capacitor circuit is further configured to selectively discharge the first capacitor in response to deassertion of the enable signal.
4. The circuit of claim 1 , wherein the second switched capacitor circuit is further configured to selectively discharge the second capacitor in response to another logic state of the clock signal.
5. The circuit of claim 1 , wherein the charge pump circuit comprises a multi-stage capacitor circuit.
6. The circuit of claim 5 , wherein a stage of the multi-stage capacitor circuit is implemented as a Dickson circuit.
7. The circuit of claim 5 , wherein a stage of the multi-stage capacitor circuit is implemented as a voltage doubler circuit.
8. The circuit of claim 1 , wherein the first switched capacitor circuit further comprises a voltage limiting circuit coupled in series with the first capacitor between the gate terminal and a ground.
9. The circuit of claim 8 , wherein the voltage limiting circuit comprises a MOSFET device having a gate terminal biased by a bias voltage.
10. The circuit of claim 1 , wherein the second switched capacitor circuit further comprises a voltage limiting circuit coupled in series with the second capacitor between the gate terminal and a ground.
11. The circuit of claim 10 , wherein the voltage limiting circuit comprises a MOSFET device having a gate terminal biased by a bias voltage.
12. The circuit of claim 1 , wherein the voltage regulator circuit is a low drop out (LDO) type circuit.