Power saving circuit for embedded battery applications

1. A battery-disconnect circuit comprising:

a latch;

a battery-disconnect subcircuit configured to control current leakage and connected to the latch, the latch configured to maintain a power supply state and a no-power supply state of the battery-disconnect subcircuit;

a power-enable subcircuit connected to the battery-disconnect subcircuit, wherein an enable signal switches the battery-disconnect subcircuit to the power supply state and an off signal switches the battery-disconnect subcircuit to the no-power supply state; and

a level shifting buffer that comprises a first n-type metal-oxide semiconductor field-effect transistor (NMOS FET) and a second NMOS FET, wherein a first gate terminal of the first NMOS FET is connected to a second gate terminal of the second NMOS FET.

2. The battery-disconnect circuit of claim 1 , wherein the battery-disconnect subcircuit comprises a p-type metal-oxide-semiconductor field-effect transistor (PMOS FET).

3. The battery-disconnect circuit of claim 2 , wherein the latch is a NOR S/R latch that comprises an input terminal and a Vcc terminal, wherein the input terminal is connected to the gate of the PMOS FET and the Vcc terminal is connected to the source of the PMOS FET.

4. The battery-disconnect circuit of claim 2 , wherein the latch is a microcontroller that comprises an IO terminal and a Vcc terminal, wherein the IO terminal is connected to the gate of the PMOS FET and the Vcc terminal is connected to the source of the PMOS FET.

5. The battery-disconnect circuit of claim 1 , wherein the level shifting buffer further comprises a p-type metal-oxide semiconductor field-effect transistor (PMOS FET), and wherein a drain terminal of the PMOS FET is connected to the first gate terminal of the first NMOS FET and the second gate terminal of the second NMOS FET.

6. The battery-disconnect circuit of claim 1 , wherein the first NMOS FET and the second NMOS FET have a Vdss≥12V and a Vgsth≥1.5V at 1 mA.

7. The battery-disconnect circuit of claim 5 , wherein the latch comprises a first inverter and a second inverter, wherein an input terminal of the first inverter is connected to a capacitor and an output terminal of the first inverter is connected to an input terminal of the second inverter, and an output terminal of the second inverter is connected to a gate terminal of the battery-disconnect subcircuit.

8. The battery-disconnect circuit of claim 1 further comprising:

a signal level shifting inverter configured to control signals to the latch.

9. The battery-disconnect circuit of claim 8 , wherein the signal level shifting inverter is configured to set the latch and switch the battery-disconnect subcircuit to the power supply state in response to the on signal.

10. The battery-disconnect circuit of claim 8 , wherein the signal level shifting inverter is configured to clear the latch and switch the battery-disconnect subcircuit to the no-power supply state in response to the off signal.

11. An image capture device comprising:

a battery;

a processor; and

a battery-disconnect circuit connected to the battery and the processor, the battery-disconnect circuit comprising:

a latch;

a battery-disconnect subcircuit configured to control current leakage and connected to the latch, the latch configured to maintain a power supply state and a no-power supply state of the battery-disconnect subcircuit;

a power-enable subcircuit connected to the battery-disconnect subcircuit, wherein an enable signal switches the battery-disconnect subcircuit to the power supply state and an off signal switches the battery-disconnect subcircuit to the no-power supply state; and

a level shifting buffer that comprises a first n-type metal-oxide semiconductor field-effect transistor (NMOS FET), a second NMOS FET, and a p-type metal-oxide semiconductor field-effect transistor (PMOS FET), wherein a drain terminal of the PMOS FET is connected to a first gate terminal of the first NMOS FET and a second gate terminal of the second NMOS FET.

12. The image capture device of claim 11 , wherein the battery-disconnect subcircuit comprises a p-type metal-oxide-semiconductor field-effect transistor (PMOS FET).

13. The image capture device of claim 12 , wherein the latch is a NOR SIR latch that comprises an input terminal and a Vcc terminal, wherein the input terminal is connected to the gate of the PMOS FET and the Vcc terminal is connected to the source of the PMOS FET.

14. The image capture device of claim 12 , wherein the latch is a microcontroller that comprises an IO terminal and a Vcc terminal, wherein the IO terminal is connected to the gate of the PMOS FET and the Vcc terminal is connected to the source of the PMOS FET.

15. The image capture device of claim 11 , wherein the level shifting buffer further comprises a p-type metal-oxide semiconductor field-effect transistor (PMOS FET), and wherein a drain terminal of the PMOS FET is connected to the first gate terminal of the first NMOS FET and the second gate terminal of the second NMOS FET.

16. The image capture device of claim 11 , wherein the first NMOS FET and the second NMOS FET have a Vdss≥12V and a Vgsth≥1.5V at 1 mA.

17. The image capture device of claim 15 , wherein the latch comprises a first inverter and a second inverter, wherein an input terminal of the first inverter is connected to a capacitor and an output terminal of the first inverter is connected to an input terminal of the second inverter, wherein an output terminal of the second inverter is connected to a gate terminal of the battery-disconnect subcircuit.

18. The image capture device of claim 11 , wherein the battery-disconnect circuit further comprises:

a signal level shifting inverter configured to control signals to the latch, wherein the signal level shifting inverter is configured to set the latch and switch the battery-disconnect subcircuit to the power supply state in response to the on signal.

19. The image capture device of claim 11 , wherein the battery-disconnect circuit further comprises:

a signal level shifting inverter configured to control signals to the latch, wherein the signal level shifting inverter is configured to clear the latch and switch the battery-disconnect subcircuit to the no-power supply state in response to the off signal.

20. An image capture device comprising:

a battery;

a processor; and

a battery-disconnect circuit connected to the battery and the processor, the battery-disconnect circuit comprising:

a battery-disconnect subcircuit configured to control current leakage;

a latch configured to maintain a power supply state and a no-power supply state of the battery-disconnect subcircuit, wherein the latch comprises a first inverter and a second inverter, wherein an input terminal of the first inverter is connected to a capacitor and an output terminal of the first inverter is connected to an input terminal of the second inverter, and an output terminal of the second inverter is connected to a gate terminal of the battery-disconnect subcircuit;

a power-enable subcircuit connected to the battery-disconnect subcircuit; and

a level shifting buffer that comprises a first n-type metal-oxide semiconductor field-effect transistor (NMOS FET) and a second NMOS FET, wherein the output terminal of the second inverter is connected to a drain terminal of the first NMOS FET, and a first gate terminal of the first NMOS FET is connected to a second gate terminal of the second NMOS FET.