7.3MHz crystal alternative ???????

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manish12

Joined: 21 Nov 2006
Posts: 1020
Helped: 31

30 Jan 2008 9:15 7.3MHz crystal alternative ???????

i am developing a project on ATMEGA8535 and it uses the crystal value 7.3MHz.

and it is very difficult to get that crystal value here.

so, any alternative for this , ?????

FvM

Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany

30 Jan 2008 12:13 Re: 7.3MHz crystal alternative ???????

Hello,

7.373 is mainly used to have exact UART baudrates. This isn't required normally. Any PC uses 24/13 as UART timebase instead. You should know the project requirements, we can't. If you utilize 461 or 922 kBaud, you probably need an "UART"-crystal, up to 115k should be possible with 16 or 24 MHz.

Regards,
Frank

manish12

Joined: 21 Nov 2006
Posts: 1020
Helped: 31

30 Jan 2008 12:23 Re: 7.3MHz crystal alternative ???????

no !,

alternative ?????

any clk circuitry for it

banjo

Joined: 24 Dec 2005
Posts: 644
Helped: 118

30 Jan 2008 14:24 7.3MHz crystal alternative ???????

What parts of your project are driving the need for this crystal? You could add an external PLL to generate this frequency, but the cost will greatly exceed the price of the crystal.
I see two alternatives.
1. Buy the crystal in quantity and stock it.
2. Recode the clock sensitive parts to use the crystals that are available to you. If you are porting someone else's code, remember that they may have chosen 7.3MHZ because it was available to them, and not because it was a hard requirement.

manish12

Joined: 21 Nov 2006
Posts: 1020
Helped: 31

30 Jan 2008 15:58 Re: 7.3MHz crystal alternative ???????

i want to go with PLL with exceed crystal cost , have any specific circuit for this situation ?

i found some crystal oscillator ckt here . will it ok for me to get 7.3Mhz
if yes how ?

http://hem.passagen.se/communication/txo.html

q: >> i need 7.3Mhz clock oscillator/ clk generator ? without crystal ??

Last edited by manish12 on 30 Jan 2008 16:16; edited 1 time in total

FvM

Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany

30 Jan 2008 16:02 Re: 7.3MHz crystal alternative ???????

For a next answer, I would appreciate a clear question, better a specification

manish12

Joined: 21 Nov 2006
Posts: 1020
Helped: 31

31 Jan 2008 18:30 Re: 7.3MHz crystal alternative ???????

q: >> i need 7.3Mhz clock oscillator/ clk generator ? without crystal ??

JunkMe

Joined: 26 Jan 2008
Posts: 20
Location: New Bedford, MA

31 Jan 2008 19:11 7.3MHz crystal alternative ???????

if you cant get parts pick anothter projekt

manish12

Joined: 21 Nov 2006
Posts: 1020
Helped: 31

31 Jan 2008 19:22 Re: 7.3MHz crystal alternative ???????

-ve

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JunkMe

Joined: 26 Jan 2008
Posts: 20
Location: New Bedford, MA

31 Jan 2008 20:03 7.3MHz crystal alternative ???????

ev-

peyro

Joined: 24 Jan 2008
Posts: 5

31 Jan 2008 21:21 Re: 7.3MHz crystal alternative ???????

Hello maybe an approach like this

http://electronicdesign.com/Articles/ArticleID/6350/6350.html

is better and cheaper. In fact I would use a tiny from atmel because development and programming tools, if I am not wrong are reused... I think that if many chips are feeded the clock output should be buffered.. if internal clock tolerance of the uC is not enough, external and comercially available crystal maybe used and its frequency arbitrary divided...

Given that this approach uses a uC, you can take advantage of this adding more task and functionalities to it like external watchdog, reset circuit, power supply monitor, etc...

hope it helps...

peyro

echo47

Joined: 07 Apr 2002
Posts: 4206
Helped: 566

01 Feb 2008 1:25 7.3MHz crystal alternative ???????

How close does it have to be to 7.3 MHz? If you can use 7.3728 MHz, then that value is in stock at DigiKey and Mouser (distributors in USA), and probably many other places.