Selectively activated three-state charge pump
This document discusses, among other things, a device for providing a DC output voltage, including a first output voltage and a second output voltage, from an input voltage. The device can include a first voltage regulator configured to provide the first output voltage when the input voltage is below a threshold voltage, and a charge pump configured to provide the second output voltage from the first output voltage in a two-state mode when the input voltage is below the threshold voltage, and to provide the first output voltage and the second output voltage in a three-state mode when the input voltage is above the threshold voltage.
1. A device for providing a DC output voltage, including a first output voltage and a second output voltage, from an input voltage, the device comprising:
a first linear regulator configured to provide the first output voltage when the input voltage is below a threshold voltage; and
a charge pump configured to provide the second output voltage from the first output voltage in a two-state mode when the input voltage is below the threshold voltage and to provide the first output voltage and the second output voltage in a three-state mode when the input voltage is above the threshold voltage.
2. The device of claim 1 , wherein the first linear regulator is configured to convert the input voltage into the first output voltage when the input voltage is below a threshold voltage; and
wherein the charge pump is configured to convert the input voltage into the first input voltage and the second output voltage when the input voltage is above the threshold voltage.
3. The device of claim 1 , comprising a second linear regulator configured to convert the input voltage into an intermediate voltage, wherein the first linear regulator is configured to convert the intermediate voltage into the first output voltage when the input voltage is below a threshold voltage, and wherein the charge pump is configured to convert the intermediate voltage into the first input voltage and the second output voltage when the input voltage is above the threshold voltage.
4. The device of claim 3 , wherein the first output voltage corresponds to half of the intermediate voltage, and wherein the second output voltage is complementary to the first output voltage.
5. The device of claim 3 , wherein the input voltage is a variable DC voltage and the first linear regulator generates a stable DC voltage for the first and second output voltages.
6. The device of claim 1 , wherein the charge pump includes a first state including a flying capacitor coupled between the first output voltage and a ground, a second state including the flying capacitor coupled between a ground and the second output voltage, and a third state including the flying capacitor coupled between the input voltage and the first output voltage.
7. The device of claim 6 , wherein the charge pump is configured to switch between the first state and the second state in a two-state mode, and to switch between the first state, the second state, and the third state in a three-state mode.
8. A method of providing a DC output voltage, including a first output voltage and a second output voltage, from an input voltage, the method comprising:
providing the first output voltage using a first linear regulator when the input voltage is below a threshold voltage;
providing the second output voltage using a charge pump configured to operate in a two-state mode when the input voltage is below the threshold voltage; and
providing the first output voltage and the second output voltage using the charge pump configured to operate in a three-state mode when the input voltage is above the threshold voltage.
9. The method of claim 8 , wherein the providing the first output voltage using the first linear regulator includes converting the input voltage into the first output voltage using the first linear regulator; and
wherein the providing the first output voltage using the charge pump includes converting the input voltage into the first output voltage using the charge pump.
10. The method of claim 8 , comprising:
converting an input voltage into an intermediate voltage using a second linear regulator;
wherein the providing the first output voltage using the first linear regulator includes converting the intermediate voltage into the first output voltage using the first linear regulator; and
wherein the providing the first output voltage using the charge pump includes converting the intermediate voltage into the first output voltage using the charge pump.
11. The method of claim 10 , wherein the providing the first output voltage includes providing a first output voltage corresponding to half of the intermediate voltage, and wherein the providing the second output voltage is complementary to the first output voltage.
12. The method of claim 10 , wherein the input voltage is a variable DC voltage and wherein converting includes providing stable DC voltages for the first and second output voltages.
13. The method of claim 8 , wherein the providing the second output voltage using the charge pump includes coupling a flying capacitor between the first output voltage and a ground in a first state, and coupling the flying capacitor between a ground and the second output voltage in a second state; and
wherein the providing the first output voltage and the second output voltage using the charge pump includes coupling the flying capacitor between the input voltage and the first output voltage in a third state.
14. The method of claim 13 , wherein the providing the second output voltage using the charge pump includes operating in a two-state mode, switching the charge pump between the first state and the second state; and
wherein the providing the first output voltage and the second output voltage using the charge pump includes operating in a three-state mode, switching between the first state, the second state, and the third state.
15. The method of claim 8 , wherein the providing the first output voltage using the first linear regulator includes providing the first output voltage with a linear regulator.
16. A circuit for providing a stable DC output voltage including a first output voltage and a second output voltage, the circuit comprising:
a first linear regulator configured to convert an input voltage into an intermediate voltage;
a second linear regulator configured to convert the intermediate voltage into the first output voltage when the input voltage is below a threshold; and
a charge pump configured to provide the second output voltage from the intermediate voltage in a two-state mode when the input voltage is below the threshold, and to provide the first output voltage and the second output voltage from the intermediate voltage in a three-state mode when the input voltage is above the threshold.
17. The circuit of claim 16 , wherein the input voltage is a variable DC voltage and the first linear regulator generates a stable DC voltage from the input voltage.
18. The circuit of claim 17 , wherein the first output voltage provided by the second linear regulator is a stable DC voltage.
19. The circuit of claim 16 , comprising:
a switching mechanism configured to couple the intermediate voltage to the second linear regulator when the input voltage is below the threshold and to bypass the second linear regulator and couple the intermediate voltage to the charge pump when the input voltage is above the threshold.