Circuits for increasing the reliability of an iontophoretic system
First Claim
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1. An iontophoretic drug delivery device comprising a controller, a high voltage supply, and a patch for delivering drugs electrically connected therebetween, the controller having a circuit comprising:
- a microprocessor selectively switchable between an operational state and a reset state for controlling delivery of current to the patch according to preprogrammed software instructions in said operational state, said microprocessor having an output line, said output line being set low in the operational state and set high in the reset state;
a crystal oscillator connected to the microprocessor to clock the microprocessor;
a transistor, a gate of which being connected to the output line, wherein current delivery to the patch is allowed to occur when the output line is low and the transistor is turned off, and current delivery is stopped when the output line is high and the transistor is turned on, wherein the microprocessor includes a watchdog timer which switches the microprocessor from the operational state to the reset state, thereby causing current delivery to be stopped by the transistor.
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Abstract
Circuits are provided for increasing the reliability of an iontophoretic drug delivery system. Such circuits detect the failure of a crystal oscillator of the system, the failure of a voltage reference of the system, or the impending failure of a battery power source of the system.
49 Citations
6 Claims
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1. An iontophoretic drug delivery device comprising a controller, a high voltage supply, and a patch for delivering drugs electrically connected therebetween, the controller having a circuit comprising:
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a microprocessor selectively switchable between an operational state and a reset state for controlling delivery of current to the patch according to preprogrammed software instructions in said operational state, said microprocessor having an output line, said output line being set low in the operational state and set high in the reset state;
a crystal oscillator connected to the microprocessor to clock the microprocessor;
a transistor, a gate of which being connected to the output line, wherein current delivery to the patch is allowed to occur when the output line is low and the transistor is turned off, and current delivery is stopped when the output line is high and the transistor is turned on, wherein the microprocessor includes a watchdog timer which switches the microprocessor from the operational state to the reset state, thereby causing current delivery to be stopped by the transistor. - View Dependent Claims (2, 3)
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4. A circuit for disabling delivery of current to a patch of an iontophoretic system, comprising:
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a microprocessor for controlling an amount of current to be delivered to the patch, said microprocessor clocked by a crystal oscillator, wherein an input/output line of said microprocessor is caused to be in a hi-impedance state upon power being initially supplied to said microprocessor; and
first and second transistors, said first transistor having a gate connected to said input/output line and a source connected to a gate of a second transistor, said second transistor having a source and drain in the current delivery pathway of the patch, wherein when said power is initially supplied to said microprocessor, said input/output line is in the hi-impedance state and said first transistor is turned on, thereby turning off said second transistor and causing the current delivery pathway to be in an open, disabled-delivery state. - View Dependent Claims (5, 6)
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Specification