| 摘要 |
An active overload detection and protection circuit for protecting a host device (e.g., an implantable cardiac therapy device) from potential damage due to high voltage transients applied to an I/O node thereof. The protection circuit includes an I/O circuit coupled to the I/O node, the I/O circuit having low-impedance and high-impedance modes, a current overload detection circuit coupled to the I/O circuit which detects a current overload condition induced by a high voltage transient, and which generates an overload detect signal in response, and, a mode changing circuit which changes the mode of the I/O circuit from the low-impedance mode to the high-impedance mode in response to the overload detect signal. The protection circuit further includes a reset circuit which generates a reset signal a prescribed time after the overload detect signal is generated, wherein the mode changing circuit is responsive to the reset signal to change the mode of the I/O circuit. The current overload detection circuit includes circuitry which ensures that the overload detect signal is generated only when an overload current flowing through the I/O circuit is greater than a prescribed threshold level for at least a prescribed time period. The mode changing circuit includes logic circuitry which generates a mode change control signal only when both the overload detect signal and a first control signal are present.
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