Have you looked at implementing it in a low power processor, such as a 16F7= 22? They consume under 500uA running at 1MHz. Not sure what the ADC consumes running at 4kHz (DTMF highest tone is 1,633Hz), but you may be able to meet your needs by running the goertzel algorithm discussed on the list a bit ago: http://www.google.com/search?q=3Dgoertzel+tone+detection Or the more efficient DTMF detections routines discussed in this TI msp430 app note: http://www.google.com/search?q=3Dslaae16 You may get even lower power with a PIC18F13K22 or similar since you can clock it more slowly and use the multiplyer for whichever algorithm you choose. If you need even more power savings, you can probably read the ADC in bursts, and go to sleep in between bursts, depending on how quickly you have to detect a tone. These chips aren't terribly expensive - ~$2.50 each for one, $1.50 each in quantity 100. The 16f722 is about $1 each in quantity 100. Looks like you'd not only get a power consumption savings, but a cost savings as well. But I don't know the power consumption of the running ADC, so you'd still have to do a bit of testing to see if it's feasible. Running it in bursts with a resistor fed capacitor, though, should get the average current to the range you need. -Adam On Fri, Mar 26, 2010 at 1:24 PM, Dwayne Reid wrote: > Good day to all. > > I'm currently working on a project where the current consumed by a > cm8870 or mt8870 DTMF decoder is a bit more than I can tolerate. =A0The > '8870 decoders need 5V @ 3-7mA and I have a little over 1ma available. > > Does anyone know of another DTMF decoder with lower operating > current? =A0Google hasn't been much help so far. > > Many thanks! > > dwayne > > -- > Dwayne Reid =A0 > Trinity Electronics Systems Ltd =A0 =A0Edmonton, AB, CANADA > (780) 489-3199 voice =A0 =A0 =A0 =A0 =A0(780) 487-6397 fax > www.trinity-electronics.com > Custom Electronics Design and Manufacturing > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- = http://chiphacker.com/ - EE Q&A site -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist