Power loss protection integrated circuit with autonomous capacitor health check
A power loss protection integrated circuit includes a storage capacitor terminal (STR), an autonomous capacitor health check circuit, and a capacitor fault terminal (CF). The capacitor health check circuit autonomously performs periodic capacitor check operations. In a check operation, current is sinked from the STR terminal for a predetermined time and in a predetermined way. If during this time the voltage on the STR terminal STR drops below a predetermined voltage, then a digital signal CF is asserted onto the CF terminal. Immediately following each capacitor check, a charging voltage is driven onto the STR terminal to recharge the external capacitors coupled to the STR terminal. In one example, the integrated circuit further includes a current switch circuit (eFuse) and a buck/boost controller. The capacitor health check circuit is only enabled during normal mode operation of the integrated circuit, and the check circuit disables boost operation during capacitor checks.
1. An integrated circuit comprising:
an input voltage terminal (VIN);
an output voltage terminal (VOUT);
a current switch circuit;
a storage capacitor terminal (STR);
a switch terminal (SW);
a feedback terminal (FB);
a buck/boost controller coupled to the switch terminal SW and to the feedback terminal FB; and
an autonomous capacitor health check circuit adapted to perform a capacitor health check operation, the capacitor health check operation comprising:
sinking a first current from the storage capacitor terminal STR during a first predetermined time duration; and
sinking a second current during a second predetermined time duration.
2. The integrated circuit of claim 1 , wherein:
the capacitor health check operation further comprises disabling a boost mode of the buck/boost controller during the first predetermined time duration and the second predetermined time duration; and
the second current is higher than the first current.
3. The integrated circuit of claim 2 , wherein:
the autonomous capacitor health check circuit comprises a plurality of registers;
a first value stored in the plurality of registers determines a magnitude of the first current; and
a second value stored in the plurality of registers determines a magnitude of the second current.
4. The integrated circuit of claim 2 , wherein the second predetermined time duration is shorter than the first predetermined time duration.
5. The integrated circuit of claim 1 , wherein:
the autonomous capacitor health check circuit comprises a first register;
a first value stored in the first register determines the first predetermined time duration; and
during the first predetermined time duration, the autonomous capacitor health check circuit detects whether a voltage on the storage capacitor terminal STR drops below a predetermined threshold voltage.
6. The integrated circuit of claim 5 , wherein:
the autonomous capacitor health check circuit comprises a second register; and
a second value stored in the second register determines the predetermined threshold voltage.
7. The integrated circuit of claim 1 , wherein:
the autonomous capacitor health check circuit comprises a register; and
a value stored in the register determines a magnitude of the first current that is sinked from the storage capacitor terminal STR.
8. The integrated circuit of claim 1 , wherein:
the autonomous capacitor health check circuit periodically performs the capacitor health check operation, further comprising detecting whether a voltage on the storage capacitor terminal STR drops below a predetermined threshold voltage within the first predetermined time duration; and
the autonomous capacitor health check circuit periodically performs the capacitor health check operation without repeated external prompting from any device outside the integrated circuit.
9. The integrated circuit of claim 1 , wherein the autonomous capacitor health check circuit comprises:
a first current source adapted to sink the first current from the storage capacitor terminal STR.
10. The integrated circuit of claim 1 , wherein:
the buck/boost controller is adapted to be coupled to an external inductor;
the buck/boost controller is adapted to operate as part of a buck converter and as part of a boost converter; and
the storage capacitor terminal STR is adapted to be coupled to an external storage capacitor.
11. The integrated circuit of claim 1 , wherein the autonomous capacitor health check circuit is disabled when the integrated circuit is not operating in a normal mode.
12. An integrated circuit, comprising:
a first terminal;
a second terminal;
an eFuse circuit that can receive a current from the first terminal and can conduct the current to the second terminal in a non-fault condition, and that is adapted to decouple the first terminal from the second terminal in a fault condition;
a third terminal;
a fourth terminal; and
an autonomous capacitor health check circuit adapted to perform a capacitor health check operation, the capacitor health check operation comprising:
sinking a first current from the fourth terminal for a first predetermined time duration;
sinking a second current from the fourth terminal for a second predetermined time duration; and
during the first predetermined time duration and the second predetermined time duration, detecting whether a voltage on the fourth terminal drops below a predetermined threshold voltage.
13. The integrated circuit of claim 12 , wherein:
the autonomous capacitor health check circuit comprises a register; and
a multi-bit digital value stored in the register determines the predetermined threshold voltage.
14. The integrated circuit of claim 12 , wherein:
the autonomous capacitor health check circuit comprises a register; and
a multi-bit digital value stored in the register determines the first predetermined time duration.
15. The integrated circuit of claim 12 , wherein:
the autonomous capacitor health check circuit comprises a bit;
a setting of the bit causes digital logic signal to be asserted onto the third terminal; and
a reading of the bit causes the bit to be reset.
16. The integrated circuit of claim 12 , wherein:
the autonomous capacitor health check circuit comprises a first current source and a second current source;
the first current source is coupled to sink the first current from the fourth terminal during the capacitor health check operation; and
the second current source is coupled to sink the second current from the fourth terminal during the capacitor health check operation.
17. The integrated circuit of claim 12 , further comprising:
a boost controller, wherein the autonomous capacitor health check circuit supplies a digital boost disable signal to the boost controller during the first predetermined time duration and the second predetermined time duration.
18. The integrated circuit of claim 12 , further comprising:
a switching converter control circuit, wherein the autonomous capacitor health check circuit supplies a digital boost disable signal to the switching converter control circuit during the first predetermined time duration and the second predetermined time duration.
19. The integrated circuit of claim 12 , further comprising:
a serial bus interface, where a multi-bit digital value stored in a plurality of sequential logic elements determines the first predetermined time duration of the capacitor health check operation;
wherein the multi-bit digital value stored in the plurality of sequential logic elements can be changed via the serial bus interface.
20. The integrated circuit of claim 12 , further comprising:
a serial bus interface, where a multi-bit digital value stored in a plurality of sequential logic elements determines the predetermined threshold voltage of the capacitor health check operation;
wherein the multi-bit digital value stored in the plurality of sequential logic elements can be changed via the serial bus interface.
21. The integrated circuit of claim 12 , wherein:
the current that the eFuse circuit can receive from the first terminal and can conduct to the second terminal in the non-fault condition can be a current of two amperes; and
the eFuse circuit can conduct the two ampere current with a resistance of less than one ohm between the first and second terminals.