AD5245 for Volume control

I am trying to use a digital potentiometer for volume control in a LM386 Amplifier circuit.

[IMG]http://i.imgur.com/7iyCyIo.png[/img]

I am using the LM386 amplifier with the above setup. The mechanical 10K pot has been replaced with a 10K AD5245 Digital pot.

During testing the resistance value is scaled up from 0 to 255. The first problem is that at the value 0, the volume should be zero but an audible tone can be heard. The second problem is due to the potentiometer being linear, after the 5th or 6th tap the volume is at "Full". I have been trying to make adjustments to make a pseudo logarithmic scale but with no luck so far. Anyone got any ideas I could try?

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  • Hi,

    The issue here is that the AD5245's attenuation is not really suited to audio applications. Figure 19 in the datasheet (attached below) shows at zero code that the gain is approximately -45dB.  There is also no shutdown feature either to eliminate the tone.  An example of digiPOT's with a shutdown feature is the AD5116 or AD5110.

    For your second point on logarithmic scale, there is a CFTL which you may find interesting, it discusses using the AD5292 digiPOT in a logarithmic audio volume control. Its titled CN-0120.

    Kind Regards,

    David

Reply
  • Hi,

    The issue here is that the AD5245's attenuation is not really suited to audio applications. Figure 19 in the datasheet (attached below) shows at zero code that the gain is approximately -45dB.  There is also no shutdown feature either to eliminate the tone.  An example of digiPOT's with a shutdown feature is the AD5116 or AD5110.

    For your second point on logarithmic scale, there is a CFTL which you may find interesting, it discusses using the AD5292 digiPOT in a logarithmic audio volume control. Its titled CN-0120.

    Kind Regards,

    David

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