A threshold detector circuit (24, 44) 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.