Controller for nerve stimulation circuit and associated systems and methods
Disclosed is a voltage monitoring circuit for use in detecting if a voltage supplied to current-generating circuit is sufficient to allow the current-generating circuit to produce a desired current. In one embodiment the circuit is designed for use in an implantable device that is configured to deliver therapeutic pulses to a patient. The voltage monitoring circuit is configured to produce a signal if a supplied voltage is insufficient to allow a current-generating circuit to deliver a requested current to a set of electrodes. In one embodiment, the voltage monitoring circuit detects a change in a difference between the voltage at a node in the current-generating circuit and the supplied voltage.
1. A voltage monitoring circuit for use with a system that delivers therapeutic pulses to a patient of the type that includes:
a voltage regulator coupleable to a battery and that is configured to produce a variable supply voltage;
a current-generating circuit configured to supply a requested current to one or more electrodes more transistors coupled to the variable supply voltage and configured to be in saturation when supplying the requested current, the voltage monitoring circuit comprising:
a reference current path that includes a transistor coupled to the variable supply voltage that is configured to produce a voltage at a terminal that tracks the variable supply voltage; and
a comparator circuit configured to produce a signal when the supply voltage produced by the voltage regulator is insufficient to allow the current-generating circuit to supply the requested current, wherein the comparator circuit has a first input coupled to the terminal of the transistor in the reference current path to sense the voltage that tracks the variable supply voltage, and a second input coupled to a terminal of the one or more transistors in the current-generating circuit to sense a voltage drop across the one or more transistors in the current-generating circuit, and wherein the comparator is configured to produce the signal that indicates the variable supply voltage produced by the voltage regulator is sufficient to allow the current-generating circuit to supply the requested current when the voltage at the second input exceeds the voltage at the first input.
2. The voltage monitoring circuit of claim 1 , wherein the first input is taken at a node that is located between the transistor in the reference current path and a constant current source.
3. The voltage monitoring circuit of claim 2 , wherein the current-generating circuit includes sets of parallelly connected transistors are wherein the second input is taken at a node that is located between the sets of parallelly connected transistors that supply the requested current.
4. The voltage monitoring circuit of claim 1 , wherein the transistor coupled to the variable supply voltage in the reference current path is biased to operate in a linear region.
5. A circuit configured to monitor if a supply voltage is insufficient to allow a current-generating circuit to cupply a requested current, comprising:
a battery;
a processor;
a programmable voltage regulator coupled to the battery and configured to produce a variable supply voltage;
a supply voltage monitoring circuit configured to produce a signal that is indicative of whether the variable supply voltage produced by the programmable voltage regulator is in sufficient to allow a current-generating circuit including one or more transistors coupled to the variable supply voltage to supply the requested current, wherein the supply voltage monitoring circuit includess:
a reference current path that includes a transistor coupled to the variable supply voltage that is configured to produce a voltage at a terminal that tracks the variable supply voltage; and
a comparator circuit having a first input coupled to the terminal of the transistor in the reference current path to sense the voltage that tracks the variable supply voltage and a second input coupled to a terminal of the one or more transistors in the current-generating circuit to sense a voltage drop across the one or more transistors in the current-generating circuit wherein the comparator is configured to produce the signal that indicates that the variable supply voltage produced by the programmable voltage regulator is insufficient to allow the current-generating circuit to supply the requested current when the voltage at the second input exceeds the voltage at the first input; and
wherein the processor is configured to receive the signal from the supply voltage monitoring circuit and is configured to execute instructions to control the programmable voltage regulator to change the variable supply voltage provided to the current-generating circuit.
6. The circuit of claim 5 , wherein the processor is configured to execute instructions that cause the processor to control the programmable voltage regulator to decrease the variable supply voltage if the signal from the supply voltage monitoring circuit indicates that the variable supply voltage is sufficient to allow the current-generating circuit to produce the requested current.
7. The circuit of claim 6 , wherein the processor is configured to execute instructions that cause the processor to wait a period of time after the processor detects the signal from the supply voltage monitoring circuit before controlling the programmable voltage regulator.
8. The circuit of claim 5 , wherein the processor is configured to execute instructions that cause the processor to control the programmable voltage regulator to increase the variable supply voltage if the signal from the supply voltage monitoring circuit indicates that the variable supply voltage is insufficient to allow the current-generating circuit to produce the requested current.
9. The circuit of claim 5 , wherein the transistor coupled to the variable supply voltage in the reference current path is biased to operate in a linear region.