Choice of crystal for UPSD32xx beware above 30MHz!

[johnpizzey9]

Posted on November 25, 2003 at 08:27

Choice of crystal for UPSD32xx beware above 30MHz!

[johnpizzey9]

Posted on May 17, 2011 at 11:56

Figure 19 of the UPSD23xx data sheet shows a crystal of between 8MHz and 40MHz attached to XTAL1 and XTAL2. However, be careful, many crystals above about 30MHz are third overtone types. These require a special circuit to pick out the third overtone and prevent the fundamental mode. They are NOT suitable for use with the USD32xx oscillator (they will oscillate at one third the frequency you expect). I know this because I've just learned the hard way!

The best option at these higher frequencies is probably an oscillator module (as used on the evaulation board).

[neil2]

Posted on May 17, 2011 at 11:56

I too, learnt the hard way about this. There were some posts a few months ago on this subject.

although a lot of xtals above 30MHz are third overtone types, fundamental mode xtals are also available. we use a 36MHz fundamental mode xtal.

[johnpizzey9]

Posted on May 17, 2011 at 11:56

I would be interested to know the supplier for your 36 MHz crystal

[neil2]

Posted on May 17, 2011 at 11:56

Hi,

We buy our 36MHz fundamental mode xtals from a company in China. called Shenzhen Jingfeng Technology Development Company e-mail

mailto:sales@szjf.com

. They provided us with samples to try out before ordering production quantities.