Tamper detector power supply with wake-up
View Patent ↗A tamper detector has tamper detection logic connected to tamper detection ports through a tamper detection interface. A real-time clock (RTC) provides a clock signal and has a battery. A processor is powered by an external power supply in a powered operational mode and has a power-off mode. In a wake-up configuration, a wake-up signal on a specific I/O port awakens the external power supply from the power-off mode to supply power to the RTC and the tamper detection interface when power from the battery is unavailable. The tamper detection ports continue to function despite removal or discharge of the battery without ESD concerns. The specific I/O port optionally may be configured for passive tamper detection.
1. A tamper detector, comprising:
a processor having a powered operational mode and a power-off mode;
an external power supply for supplying power to the processor in the powered operational mode; and
a real-time clock (RTC) module, including:
a plurality of tamper detection ports for connection to tamper detection elements protecting a module;
tamper detection logic connected to the tamper detection ports by way of a tamper detection interface; and
a specific input/output (I/O) port for connection in a wake-up configuration to a control input of the external power supply;
wherein the RTC module is powered by the external power supply in the powered operational mode and by a battery in the power off mode; and
wherein a wake-up signal on the specific I/O port in the wake-up configuration wakes up the external power supply from the power off mode to supply power.
2. The tamper detector of claim 1 , wherein the RTC module provides the wake-up signal in an isolated event and in a periodic timed sequence.
3. The tamper detector of claim 1 , further comprising a buffer connecting the tamper detection logic to the specific I/O port, wherein the buffer assumes a high impedance output state to assert the wake-up signal, and a low impedance output state to de-assert the wake-up signal when power from the battery is available.
4. The tamper detector of claim 3 , wherein a source of power for the external power supply is connectable to assert the wake-up signal for the external power supply in the high impedance output state of the buffer in the wake-up configuration of the specific I/O port.
5. The tamper detector of claim 4 , wherein the buffer drives the specific I/O port to de-assert the wake-up signal.
6. The tamper detector of claim 4 , wherein the specific I/O port is connectable between one of the tamper detection elements protecting the module and the tamper detection logic in a tamper detection configuration in which the specific I/O port is disconnected from the source of power for the external power supply, and wherein the tamper detection logic provides a control signal to the buffer causing the buffer to assume the high impedance output state in the tamper detection configuration and enabling a passive tamper detection input path through the specific I/O port.
7. The tamper detector of claim 6 , wherein the specific I/O port is connectable in the tamper detection configuration to provide a passive tamper detection signal from the tamper detection element to the tamper detection logic when power from either or both of the internal power supply and the battery is available.
8. The tamper detector of claim 1 , wherein the tamper detection logic detects tampering through the tamper detection ports even when the battery is unavailable.
9. The tamper detector of claim 1 , wherein the tamper detection interface is configurable to connect at least two ports for the tamper detection logic to propagate an active tamper signature signal in the tamper detection elements and receive a corresponding active tamper detection signal.
10. The tamper detector of claim 9 , wherein the tamper detection logic controls the direction of propagation of the signature signal and reception of the active tamper detection signal through the at least two ports.
11. The tamper detector of claim 9 , wherein the tamper detection interface is configurable alternatively to connect the at least two ports to provide a passive tamper detection signal from the tamper detection elements in the protected module through the tamper detection ports to the tamper detection logic.
12. The tamper detector of claim 1 , wherein the tamper detection interface includes triggers through which the tamper detection ports connect to the tamper detection logic, the triggers having a predetermined output signal level as a function of a variable input signal level.
13. The tamper detector of claim 1 , wherein the tamper detection interface includes level shifters through which the tamper detection ports connect to the tamper detection logic when the tamper detection ports are powered by the battery.
14. The tamper detector of claim 1 , further comprising a dummy pad connected to receive power from the external power supply and to power an electrostatic discharge (ESD) bus connected to the tamper detection ports and the specific I/O port, when power from the battery is unavailable.
15. The tamper detector of claim 1 , further comprising:
a power management controller for monitoring supply of power from the external power supply and asserting a low voltage warning signal when a voltage from the external power supply is less than a threshold,
wherein the RTC module is powered from the battery in response to assertion of the low voltage warning signal, and wherein power is supplied from the external power supply instead of the battery in response to de-assertion of the low voltage warning signal when the voltage from the external power supply is greater than the threshold.
16. The tamper detector of claim 15 , wherein assertion of the low voltage warning signal is latched while the voltage from the external power supply is less than the threshold.
17. The tamper detector of claim 15 , wherein the processor has a reduced voltage mode of operation in which the low voltage warning signal is disabled, and power is supplied to the RTC module and the tamper detection interface from the battery during the reduced voltage mode of operation.