In general, this disclosure describes techniques for capacitive
digit-to-analog converter (CAPDAC) resetting in an implantable medical
device (IMD) analog-to-digital converter (ADC). The CAPDAC of an IMD ADC
may occasionally be reset to increase the accuracy of its output. The
output of the CAPDAC may be disconnected from a negative feedback input
of an integrator and connected to a pseudo load during the reset.
Disconnecting the CAPDAC from the negative feedback input of the
integrator reduces the affect of the reset on the integrator. During the
reset of the CAPDAC, the negative feedback input of integrator is coupled
to a sample and hold capacitor, which temporarily provides an input
approximately equal to a previous, e.g., immediate, value of the output
of CAPDAC prior to the reset. Thus, the resetting of the CAPDAC is done
in such a manner that the affect of the reset on integrator is
substantially reduced or eliminated.