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Topic: Can we use 3.579545MHz crystal instead of 3.57MHz (Read 2486 times) previous topic - next topic


I'ma making a cellphone controlled land rover with MT8870 DTMF decoder IC, but it is not woking,i'm using 3.579545Mhz crystal,but i saw in many circuits, the MT8870 is given 3.57MHz crystal, is there any issue in using 3.579545Mhz??
Thank You :)


Apr 30, 2013, 04:03 pm Last Edit: Apr 30, 2013, 04:05 pm by cjdelphi Reason: 1
Check to make sure you're using the correct loading capacitors for the crystal... or it wont work at all...


that's interesting, i see a lack of capacitors, it's obviously not logic gate oscillator? , so what are you using for your circuit?


... but it is not woking

Maybe your wok needs more oil.

Seriously, it's been a long time since I used a DTMF decoder chip but I seem to remember that they don't work very well if the input signal is too large, so that would be a good thing to check.



I agree with florestra.  Too much input causes clipping which creates too many high amplitude harmonics and just confuses the situation.  Make sure your input is low enough and fairly sinusoidal.


Thank you all :)
I checked it, the circuit i saw, the  INH and PWDN pins are grounded, i just removed that ground connection and made it open bcoz i read that there are internal pull down resistors for that pins, now when i removed that connection and as floresta told i reduced the input amplitude now it is working good. :)

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