Pressure sensor with increased sensitivity for use with an implantable medical device

A circuit for detecting a pressure change of a body fluid, comprising:

• a pressure sensor comprising a measurement capacitor responsive to pressure changes of the body fluid;
• a switch coupled to the measurement capacitor;
• a first current source coupled to the switch;
• a second current source coupled to the switch;
• and
• a timing circuit, the switch coupling the first current source to the measurement capacitor for charging the measurement capacitor at a first charge rate during a first charge period of an integration cycle, and the switch, in response to a switch signal produce by the timing circuit, coupling the second current source to the measurement capacitor for charging the measurement capacitor at a second charge rate during a second charge period of the integration cycle, the pressure sensor producing a signal indicative of a pressure change of the body fluid imparted to the measurement capacitor.

A body implantable pressure sensing apparatus, comprising:

• an implantable medical device;
• a lead coupled to the implantable medical device;
• and
• a pressure sensor provided on the lead, the pressure sensor, comprising:
• a measurement capacitor responsive to pressure changes of a body fluid;
• a switch coupled to the measurement capacitor;
• a first current source coupled to the switch;
• a second current source coupled to the switch;
• and
• a timing circuit, the switch coupling the first current source to the measurement capacitor for charging the measurement capacitor at a first charge rate during a first charge period of an integration cycle, and the switch, in response to a switch signal produce by the timing circuit, coupling the second current source to the measurement capacitor for charging the measurement capacitor at a second charge rate during a second charge period of the integration cycle, the pressure sensor producing a signal indicative of a pressure change of the body fluid imparted to the measurement capacitor.

A method of obtaining physiologic data of a body tissue using a capacitive pickoff sensor, the capacitive pickoff sensor comprising a measurement capacitor responsive to conditions of a physiologic condition, the method comprising:

• charging, during a first charge period of an integration cycle, the measurement capacitor at a first charge rate;
• charging, during a second charge period of the integration cycle, the measurement capacitor at a second charge rate;
• and
• producing, using the lengths of the first and second charge periods of the measurement capacitor, a signal indicative of physiologic condition of the body fluid imparted to the measurement capacitor.

A body implantable physiologic condition sensing apparatus, comprising:

• an implantable medical device;
• a sensor housing coupled to the implantable medical device;
• and
• a capacitive pickoff sensor provided in the or housing, the sensor, comprising:
• a measurement capacitor responsive to physiologic condition of a body tissue;
• a switch coupled to the measurement capacitor;
• a first current source coupled to the switch;
• a second current source coupled to the switch;
• and
• a timing circuit, the switch coupling the first current source to the measurement capacitor for charging the measurement capacitor at a first charge rate during a first charge period of an integration cycle, and the switch, in response to a switch signal produce by the timing circuit, coupling the second current source to the measurement capacitor for charging the measurement capacitor at a second charge rate during a second charge period of the integration cycle, the physiologic condition sensor producing a signal indicative of a physiologic condition of the body tissue imparted to the measurement capacitor.