Switch validation circuit and method
A switch-operated therapeutic agent delivery device is described. Embodiments of the operated therapeutic agent delivery device include a switch that can be operated by a user, a device controller connected to the switch through a switch input where the device can actuate the device when certain predetermined conditions are met, following performance of both a digital switch validation test and an analog switch validation test.
1. A drug delivery device adapted to validate the operation of a user-selectable activation switch to deliver a dose of drug, the device comprising:
a battery having a battery voltage;
a switch configured to be activated by a user to deliver a dose of drug, the switch having a low voltage side and a high voltage side;
a first input line on the high side and a second input line on the low side, wherein the first and second input lines are connected to the battery;
a first analog test input line on the high side and a second analog test input line on the low side;
a first digital test input line on the high side and a second digital test input line on the low side;
a controller configured to perform a digital validation of the switch following a release event of the switch and to perform an analog validation of the switch following the release event, wherein the controller is further configured to initiate a failure mode for the drug delivery device if the analog validation of the switch fails.
2. The device of claim 1 , further comprising a circular buffer configured to store a plurality of sequential samples from an input line on the low voltage side of the switch, wherein the newest sample replaces the oldest sample.
3. The device of claim 1 , wherein the controller is configured to sequentially sample an input line on the high voltage side of the switch, store a window of sequential samples, and compare a plurality of more recent sequential samples to a plurality of older sequential samples within the stored window of samples to detect the release event.
4. The device of claim 1 , wherein the first and second analog test input lines are connected to the controller, and further wherein the controller configured to fail the analog validation if a voltage on the first analog test line is below a first predetermined fraction of the battery voltage or if a voltage on the second analog test line is greater than a second predetermined fraction of the battery voltage.
5. The device of claim 1 , wherein the first and second analog test input lines are connected to the controller, and further wherein the controller configured to fail the analog validation if a voltage on the first analog test line is less about 0.8 times the battery voltage or if a voltage on the second analog test line is greater than about 0.2 time the battery voltage.
6. The device of claim 1 , wherein the first and second digital test input lines are connected to the controller, and further wherein the controller is configured to fail the digital validation if a value of the first digital test input line does not match a value of the first input line or if a value of the second digital test input line does not match a value of the second input line.
7. The device of claim 1 , wherein the first and second digital test input lines are connected to the controller, and further wherein the controller is configured to fail the digital validation if the first digital input line is low or if the second digital input line is high.
8. The device of claim 1 , wherein the controller is further configured to perform the analog validation of the switch and the digital validation of the switch following a second release of the switch within less than about 100 msec.
9. A drug delivery device adapted to validate the operation of a user-selectable activation switch to deliver a dose of drug, the device comprising:
a battery having a battery voltage;
a switch configured to be activated by a user to deliver a dose of drug, the switch having a low voltage side and a high voltage side;
a first input line on the high side and a second input line on the low side, wherein the first and second input lines are connected to the battery;
a first analog test input line on the high side and a second analog test input line on the low side, wherein the first and second analog test inputs lines are connected to a controller; and
a first digital test input line on the high side and a second digital test input line on the low side, wherein the first and second digital test input lines are connected to the controller;
wherein the controller is configured to perform a digital validation of the switch, following a second release of the switch within a predetermined time period, and to perform an analog validation of the switch following the second release of the switch within the predetermined time period, further wherein the controller is configured to fail the analog validation if a voltage on the first analog test line is below a first predetermined fraction of the battery voltage or if a voltage on the second analog test line is greater than a second predetermined fraction of the battery voltage, and to fail the digital validation if the first digital input line is low or if the second digital input line is high;
and wherein the controller initiates a failure mode for the drug delivery device if the analog validation of the switch fails.