Low voltage detection system
View Patent ↗A low voltage detection (LVD) system for a logic device includes a first LVD circuit ( 110 ) to provide an indicator when a supply pin voltage ( 109 ) falls below a first voltage level, and a second LVD circuit ( 116 ) to provide an interrupt ( 118 ) when the supply pin voltage falls below a second voltage level. In one embodiment, the second LVD circuit consumes more power than the first LVD circuit, and is therefore selectively enabled. In one embodiment, when the supply pin voltage is between the first and second voltage levels and the logic device is in a stop or low power mode, the second LVD circuit is periodically enabled to monitor the supply pin voltage. After the supply pin voltage falls below the second voltage level, the logic device is placed in a safe state where the logic device is inhibited from acknowledging interrupts until the supply pin voltage rises above the first voltage level.
1. An integrated circuit comprising:
a power supply pin for receiving power from a power source;
a first voltage detection circuit having an output to provide a first voltage detection signal indicative of a first voltage level of the power supply pin;
a second voltage detection circuit having an output to provide a second voltage detection signal indicative of a second voltage level of the power supply pin, the second voltage level different from the first voltage level;
a central processing unit, the central processing unit configured to be powered from power received via the power supply pin;
an interrupt handler operably coupled to the central processing unit, the interrupt handler responsive to a set of at least one interrupt;
an interrupt handler control circuit controlling the responsiveness of the interrupt handler to the set of at least one interrupt, the interrupt handler control circuit is responsive to the first voltage detection signal and responsive to a first signal having a first signal state which is at least indicative that the voltage level of the power supply pin had dropped below the second voltage level as indicated by the second voltage detection signal, wherein when the first signal is at the first signal state, the interrupt handler control circuit enables the interrupt handler to be responsive to the set of at least one interrupt when the first voltage detection signal indicates that the voltage level of the power supply pin is above the first voltage level.
2. The integrated circuit of claim 1 wherein the first signal is set to the first signal state via a processing operation of the central processing unit.
3. The integrated circuit of claim 2 further comprising a register including contents, the signal state of the first signal being dependent upon the contents of the register, the contents of the register being programmable by the processing operation of the central processing unit.
4. The integrated circuit of claim 2 wherein:
the output of the second voltage detection circuit is coupled to the interrupt handler, wherein the second voltage detection signal indicating that the voltage level of the power supply pin is below the second voltage level generates an interrupt;
the central processing unit performs the processing operation to set the first signal to the first signal state at least in response to the interrupt generated when the second voltage detection signal indicates that the voltage level of the power supply pin is below the second voltage level.
5. The integrated circuit of claim 1 wherein the integrated circuit has a low power stop mode wherein the second voltage detection circuit is disabled from providing the second voltage detection signal when the integrated circuit is in the low power stop mode.
6. The integrated circuit of claim 1 further comprising:
a wakeup circuit having an output to enable the second voltage detection circuit to provide the second voltage detection signal when at least the integrated circuit is in a low power stop mode and the first voltage detection signal indicates that the voltage level of the power supply pin is below the first voltage level.
7. The integrated circuit of claim 6 wherein the output of the wake up circuit enables the second voltage detection circuit to provide the second voltage detection signal when at least the integrated circuit is in a low power stop mode, the first voltage detection signal indicates that the voltage level of the power supply pin is below the first voltage level, and the first signal is at a second signal state different than the first signal state.
8. The integrated circuit of claim 6 wherein the wakeup circuit is a periodic wakeup circuit, wherein the output provides a periodic signal to enable the second voltage detection circuit to provide the second voltage detection signal when at least the integrated circuit is in a low power stop mode and the first voltage detection signal indicates that the voltage level of the power supply pin is below the first voltage level.
9. The integrated circuit of claim 1 wherein the interrupt handler control circuit controls the responsiveness of the interrupt handler to the set of at least one interrupt by gating the at least one interrupt signal into the interrupt handler.
10. A system capable of battery powered operation including the integrated circuit of claim 1 and further comprising:
a battery coupled to the power supply pin for supplying power to the power supply pin; and
an external peripheral operably coupled to the integrated circuit via at least one signal line pin of the integrated circuit.
11. The system of claim 10 further comprising:
a power storage capacitor coupled to the power supply pin.
12. In a data processing system having an interrupt handler selectively responsive to a set of at least one interrupt, an method comprising:
receiving power from a power source at a power supply pin;
providing a first voltage detection signal indicative of a first voltage level of the power supply pin;
providing a second voltage detection signal indicative of a second voltage level of the power supply pin, the second voltage level different from the first voltage level;
providing a first signal having a first signal state which is at least indicative that the voltage level of the power supply pin had dropped below the second voltage level as indicated by the second voltage detection signal; and
when the first signal is at the first signal state, enabling the interrupt handler to be responsive to the set of at least one interrupt when the first voltage detection signal indicates that the voltage level of the power supply pin is above the first voltage level.
13. The method of claim 12 further comprising:
generating an interrupt when the second voltage detection signal indicates that the voltage level of the power supply pin is below the second voltage level; and
setting the first signal to the first signal state at least in response to the interrupt generated when the second voltage detection signal indicates that the voltage level of the power supply pin is below the second voltage level.
14. The method of claim 12 further comprising not providing the second voltage detection signal when the data processing system is in a low power stop mode.
15. The method of claim 12 further comprising:
providing the second voltage detection signal when at least the integrated circuit is in a low power stop mode and the first voltage detection signal indicates that the voltage level of the power supply pin is below the first voltage level.
16. The method of claim 12 further comprising:
providing the second voltage detection signal when at least the integrated circuit is in the low power stop mode, the first voltage detection signal indicates that the voltage level of the power supply pin is below the first voltage level, and the first signal is at a second signal state different than the first signal state.
17. The method of claim 12 further comprising:
periodically providing the second voltage detection signal when at least the integrated circuit is in the low power stop mode and the first voltage detection signal indicates that the voltage level of the power supply pin is below the first voltage level.
18. The method of claim 12 further comprising gating the at least one interrupt signal to control the responsiveness of the interrupt handler to the set of at least one interrupt.
19. The method of claim 12 further comprising:
providing a central processing unit configured to be powered from power received via the power supply pin.
20. The method of claim 19 further comprising:
the central processing unit performing a processing operation to set the first signal to the first signal state.