Low power cochlear implants

Abstract

The disclosure features systems for providing auditory signals to a subject. The systems include a sensor front-end circuit configured to be connected to an acoustic sensor and to convert analog signals received from the acoustic sensor to digital electric signals. The systems further include a sound processor circuit configured to be connected to the sensor front-end circuit and receive the electric signals provided by the sensor front end circuit. The sound processor includes multiple filters that spectrally decompose the received electrical signals into multiple spectral channels during operation of the system. The multiple spectral channels include at least a low frequency channel and a high frequency channel and the sound processor circuit is configured to operate the low frequency channel at a sample rate lower than a sample rate of the high frequency channel.

What is claimed is: 
     
         1 . An implantable system for providing auditory signals to a subject, the system comprising:
 a sensor front-end circuit configured to be connected to an acoustic sensor and to convert analog signals received from the acoustic sensor to digital electric signals; and   a sound processor circuit configured to be connected to the sensor front-end circuit and receive the electric signals provided by the sensor front end circuit;   wherein:
 the sound processor circuit comprises multiple filters that spectrally decompose the received electrical signals into multiple spectral channels during operation of the system; 
 the multiple spectral channels comprise at least a low frequency channel and a high frequency channel; and 
 the sound processor circuit is configured to operate the low frequency channel at a sample rate lower than a sample rate of the high frequency channel. 
   
     
     
         2 . The system of  claim 1 , wherein during operation of the system, the system is configured to send a clock signal and a control signal into a gate, and use the output of the gate to clock-gate filters of the spectral channels that are not used to provide the auditory signals. 
     
     
         3 . The system of  claim 1  or  claim 2 , wherein the sensor front-end circuit comprises:
 a charge amplifier circuit; 
 a programmable gain circuit; and 
 an analog-to-digital converter (ADC) circuit. 
 
     
     
         4 . The system of any one of  claims 1  to  3 , wherein the sound processor circuit comprises a reconfigurable filter bank that include the multiple filters, and the reconfigurable filter bank is configured to change the number of spectral channels used to provide auditory signals. 
     
     
         5 . The system of  claim 4 , wherein the sound processor circuit is reconfigurable to operate in 4-channel, 6-channel, or 8-channel modes. 
     
     
         6 . The system of  claim 4 , wherein power consumption of the sound processor circuit is linear to the number of operating spectral channels within 15% or less. 
     
     
         7 . The system of  claim 4 , wherein the reconfigurable filter bank is configured to adjust a bandwidth and center frequency of at least one of the filters. 
     
     
         8 . The system of  claim 4 , wherein the multiple filters are configured to receive coefficients signals input that are quantized to 8-bit precision. 
     
     
         9 . The system of any one of  claims 1  to  8 , comprising a waveform stimulator that comprises:
 a digital waveform interface circuit; 
 an electrode switch matrix; and 
 a current source. 
 
     
     
         10 . The system of  claim 9 , wherein the waveform stimulator is configured to provide a waveform shape that is more energy-efficient than a rectangular waveform with the same pulse width. 
     
     
         11 . The system of  claim 9 , wherein the waveform stimulator is configured to provide a plurality of waveform shapes; and
 the system comprises a calibration circuit configured to measure hearing thresholds for the plurality of waveform shapes and select a waveform shape having a low energy.   
     
     
         12 . The system of  claim 9 , wherein the waveform stimulator is configured to provide a waveform and to adjust the shape of the waveform. 
     
     
         13 . The system of  claim 9 , wherein the waveform stimulator comprises only one current source. 
     
     
         14 . The system of  claim 9 , wherein during operation, the system consumes 600 μW or less during normal conversation. 
     
     
         15 . An implantable system for providing auditory signals to a subject, the system comprising:
 a sound processor circuit comprising multiple filters that spectrally decompose received electrical signals into multiple spectral channels during operation of the system; and   a waveform stimulator comprising a digital waveform interface circuit and an electrode switch matrix, wherein the waveform stimulator is configured to receive output signals from the multiple spectral channels and to generate an auditory signal.   
     
     
         16 . The system of  claim 15 , wherein the waveform stimulator comprises a two-stage level shifter that connects the digital wave form interface circuit and the electrode switch matrix. 
     
     
         17 . The system of  claim 15 , wherein the waveform stimulator comprises a single current source. 
     
     
         18 . The system of  claim 15 , wherein the waveform stimulator comprises a fast-settling current source. 
     
     
         19 . The system of  claim 15 , wherein the waveform stimulator is configured to generate a waveform shape which has an energy of 28% or less than that of a rectangular waveform with the same total pulse width. 
     
     
         20 . A method for providing auditory signals to a subject, the method comprising:
 determining a waveform using a heuristic algorithm wherein the waveform shape comprises a cathodic phase and an anodic phase; and each of the cathodic phase and anodic phase differs in shape from a cathodic phase and an anodic phase in a rectangular waveform.   
     
     
         21 . The method of  claim 20 , comprising:
 generating an electrical current pulse based on the determined waveform; and   applying the generated current pulse to stimulate auditory nerves of the subject.   
     
     
         22 . The method of  claim 21 , wherein the cathodic phase exponentially decreases over time. 
     
     
         23 . The method of any one of  claims 20  to  22 , wherein the waveform shape is determined based on a parameter selected from a group consisting of a phase width, duty cycle, and number of steps/width of the heuristic algorithm. 
     
     
         24 . The method of and one of  claim 23 , wherein the determined waveform has an energy of 28% or less than that of a rectangular waveform with a same total pulse width. 
     
     
         25 . The method of  claim 21 , comprising:
 providing a plurality of current pulses with different waveform shapes to the subject using the waveform stimulator;   measuring hearing thresholds for the different waveform shapes; and   selecting a waveform shape with a lower energy for the measured threshold than another waveform shape.   
     
     
         26 . The method of any of  claims 20  to  25 , wherein the steps are implemented before implanting the waveform stimulator to the subject. 
     
     
         27 . The method of any of  claims 20  to  25 , wherein the steps are implemented after implanting the waveform stimulator to the subject. 
     
     
         28 . The method of  claim 21 , comprising:
 detecting vibration signals using an acoustic sensor;   generating electric signals by processing the detected vibration signals using a sensor front-end circuit;   spectrally decomposing the electric signals using a sound processor circuit to generate decomposed information; and   using the decomposed information to apply the generated current pulse to multiple spectral channels for stimulating auditory nerves of the subject.   
     
     
         29 . The method of  claim 28 , wherein multiple spectral channels receive differently scaled amplitudes of the wave form. 
     
     
         30 . The method of  claim 28 , comprising reconfiguring the number of spectral channels used to stimulate the auditory nerves.