A threshold detector circuit configured to receive a signal from an acoustic sensor element and produce an output signal to wake up an acoustically controlled device, the threshold detector circuit comprising: a switch having an input configured to be coupled to an output of the acoustic sensor element to receive an output signal from the acoustic sensor element, a control port that receives a control signal, and a first output port and a second output port; a first analog front end having an input and an output, wherein the input of the first analog front end is coupled to the first output port of the switch ; a second analog front end having an input and an output, wherein the input of the second analog front end is coupled to the second output port of the switch ; a first analog-to-digital converter having an input coupled to the output of the first analog front end , having an output, and which operates at a first power level; a second analog-to-digital converter having an input coupled to the output of the second analog front end and having an output, and which operates at a second higher power level, relative to the first power level; a digital voltage level detector having an output, a first input, and a second input, wherein the first input of the digital voltage level detector is coupled to the output of the first analog-to-digital converter , wherein the second input of the digital voltage level detector is coupled to the output of the second analog-to-digital converter , wherein the output of the digital voltage level detector is coupled to the control port of the switch , and wherein the digital voltage level detector is configured to produce the control signal at the control port that selects the second output port of the switch based on a determination that a first digitized output signal from the first analog-to-digital converter meets a threshold criteria. a switch having an input configured to be coupled to an output of the acoustic sensor element to receive an output signal from the acoustic sensor element, a control port that receives a control signal, and a first output port and a second output port; a first analog front end having an input and an output, wherein the input of the first analog front end is coupled to the first output port of the switch ; a second analog front end having an input and an output, wherein the input of the second analog front end is coupled to the second output port of the switch ; a first analog-to-digital converter having an input coupled to the output of the first analog front end , having an output, and which operates at a first power level; a second analog-to-digital converter having an input coupled to the output of the second analog front end and having an output, and which operates at a second higher power level, relative to the first power level; a digital voltage level detector having an output, a first input, and a second input, wherein the first input of the digital voltage level detector is coupled to the output of the first analog-to-digital converter , wherein the second input of the digital voltage level detector is coupled to the output of the second analog-to-digital converter , wherein the output of the digital voltage level detector is coupled to the control port of the switch , and wherein the digital voltage level detector is configured to produce the control signal at the control port that selects the second output port of the switch based on a determination that a first digitized output signal from the first analog-to-digital converter meets a threshold criteria. <EOS>