a high shunt regulator provides precise voltage over process , temperature , power supply , and foundries . the hv level is settable by a digital control bits such as fuse bits . a filter network filters out the ripple noise and charge transient . a tracking capacitor divider network speeds up response time . a fractional band gap reference provides fractional bandgap voltage and current , and operates at low power supply and has superior power supply rejection . it is unsusceptible to substrate hot carrier effect . it exposes very little to drain induced barrier lowering effect . the bandgap core has better than conventional transient response and stability . one embodiment has adjustable level control . complementary tc trimming allows efficient realization of zero temperature coefficients of current and voltage . higher order curvature correction of voltage and current is integrated . replica bias for the control loop is presented . a binary and approximation complementary tc search trimming is described . a zero tc fractional voltage less than the theoretical bandgap voltage is realizable . the bandgap core has a filtering mechanism to reject high frequency noise . a low power startup circuit powers up the bandgap . the bandgap also has variable impedance .