Hi,
We are using OPA1664 opamp as an 8th order low pass filter, having a sharp cut off. Finally, the audio is sent to the headphone amplifier TPA6111A2.
We are thinking of using audio codec and implement the low pass filter in it. Is it possible to implement low pass filter in the audio codec and can you advise for the particular part number.
Regards,
Tapas
Hi Collin,
Right now we are using fully analog implementation. I am attaching the block diagram (Fig.1) for the clear picture. I have not included details of the sub-circuits such as microphone bias voltage, etc.
Working: The signal from the microphone is band-limited to 400 Hz through a quad op-amp IC (designed through TI filter design tool), and then it's power is increased by class D amplifier, the output of which is attached to the 8 ohm 700mW speaker. The signal after volume control pot is also sent to the headphone amplifier and then to the 3.5 mm socket, for attaching headphone.
Fig.1 (Block Diagram)
While designing filter, lots of specialized passive components such as 5% tolerance capacitors are required, which are difficult to procure from the supplier, which results in longer lead time.
Requirement: We are sending data band-limited to 400 Hz, hence 16 bit ADC will be good enough for us. We want to change the volume and output should be driven by a class D /AB amplifier. It should have a separate 3.5 mm audio out provision. The important requirement is of the high roll off 120 dB/decade.
While searching for the audio-codecs. I found out audio-codec with miniDSP.
Can the above requirement be fulfilled by audio-codecs, can you specify the part number which fulfill our requirement. Is there any other alternative which can be used.
Regards,
Tapas
