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Topic: Can we use 3.579545MHz crystal instead of 3.57MHz (Read 2042 times) previous topic - next topic

s_premkumar999

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 :)

cjdelphi

#1
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...


edit...




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

floresta

Quote
... 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.


Don

DirtBiker

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.

s_premkumar999

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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