Digital noise cancelling stethoscope

Question

We are designing a digital stethoscope with noise cancelling having two Digital MEMs microphones - one for listening to the Heart and lung sounds and one for the environment for noise cancellation. We need Audio codec with programmable DSP and headphone amplifier for the purpose. the ADAU1850 seems to be an overkill. Please suggest the appropriate part which fits the requirement. Shall we be needing a preamplifier like MAX9813H too in this case?

DaveThib · Accepted Answer

Hello plawat, 
 
 I do not understand why you think this part is overkill? It has what you need to do what you are asking to do. I would argue you should use the ADAU1860 ( ADAU1860ADAU1860‑1 Datasheet and Product Info | Analog Devices ) To do noise cancellation you need a low latency path which is the fast DSP. Then you need to do some other processing that does not have to be as fast so the HiFi core is good for that and to calculate new coefficients for the filters running in the fast DSP. Then you need the preamps and ADC inputs for the mics and of course the headphone outputs. The only thing that is not needed for you is the analog pre amp sections. 
 This part has a HiFi core which requires a license to be able to program it. 
 The part you are looking at, the ADAU1850 does not have the HiFi core so it is much simpler but will not be as capable for your application. 
 
 We have another similar product that has a SigmaDSP core so you can use SigmaStudio to program it and that is free. It is almost the same part: 
 ADAU1787 Datasheet and Product Info | Analog Devices 
 
 This one has a variant that might be interesting to you. It has half the ADCs and half the DACs. So a Mono DAC. 
 ADAU1788 Datasheet and Product Info | Analog Devices 
 
 Then there is another part we have that is newer that has a more capable fast DSP but it uses a HiFi core. The other change in this part is that the headphone amplifier is a Class-D amp so it is very power efficient! 
 ADAU1797 Datasheet and Product Info | Analog Devices

I hope this helps... 
 Dave T)

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