Patent ID: 7535285

Claim:
A reference circuit comprising: first and second reference circuit blocks; first and second controllable current sources connected to supply current through the first and second reference circuit blocks respectively; an amplifier having non-inverting and inverting inputs responsive to the voltages developed by the first and second reference circuit blocks respectively and having an output connected to control the currents provided by the first and second current sources; an output stage having a reference output controlled by the output of the amplifier; and start-up circuitry having: a latch having an output indicating its state and being responsive to a signal indicative of the output from the reference output to latch from a first state into a second state when that signal passes a first threshold; an initialization circuit block having an inverter that receives a power down signal, wherein the initialization circuit is coupled to the current sources, the output of the amplifier, and to the output stage, and wherein the initialization circuit includes a plurality of transistors coupled in series with one another that are each controlled by the inverter; a switch that is coupled to at least one of the plurality of transistors of the initialization circuit block and that is responsive to the output of the latch to supply a control signal, when the latch is in the first state, to control the first and second current sources and that is switched off when the latch is in the second state.