Topics

3.3V clock oscillators on Type AD9850m and AD9851 modules

Steven Dick
 

Hi all. I was surprised to find, in another yahoo group that many of the ebay AD9850 and AD9851 modules use a 3.3v clock oscillator.  In fact, 3.3V can be seen on some of them.  I have one Type II AD9850 module and two Type II AD9851 modules.  The 30 MHz oscillators on the AD9851 modules run hot to the touch, and I suspect they are 3.3V.  Now the questions:
1. Has anyone had failures on these modules after operating them for several hours or days?
2. Has anyone tried to mod these by adding two diodes in series with the power lead on the crystal oscillator?  I have seen this "fix" on the web
3. Has anyone found a low cost footprint compatible 30 MHz 5V crystal oscillator that can be retrofitted?

I greatly dislike operating modules under conditions they are not rated for (either run at 5V and operate a 3.3V part this way and hope it doesn't fail or run the module at 3.3V and have lower upper frequency limit on the AD9850 or AD9851 not to mention incompatibility with external circuitry running at 5V. So in addition to possible counterfeit parts and poorly performing or mis-designed filter circuitry, we also have to worry about omissions in any information about what voltage the module is designed to operate at.

Caveat Emptor.

"Digital Steve", K1RF


Alfredo Mendiola Loyola
 

I use thes 30 mhz oscillators:


They work with 5V an are SMD.

I purchased these on arrow.com, they accept paypal.

See the datasheet this model have low jitter.

If you need the eagle library for this part let me know.

Regards.
Alfredo Mendiola Loyola
Lima, Peru

Weddig, Henning-Christof <Henning-Christof.Weddig@...>
 

indeed it is not a good idea to power up a 3.3 V osc wiht overvoltage.

There are reoprts on tjhe intrnet where users have roported of large instabilities and even failure of an overpowered osc.

So the best idea is to put two diodes in series but besto only to the osc and not the DDs as its perfomnace may degrade -- if i read the data sheet of the DDS correctly

Hening
DK5LV

Am 28.01.2016 um 14:21 schrieb sbdick@... [PHSNA]:

Hi all. I was surprised to find, in another yahoo group that many of the
ebay AD9850 and AD9851 modules use a 3.3v clock oscillator. In fact,
3.3V can be seen on some of them. I have one Type II AD9850 module and
two Type II AD9851 modules. The 30 MHz oscillators on the AD9851
modules run hot to the touch, and I suspect they are 3.3V. Now the
questions:
1. Has anyone had failures on these modules after operating them for
several hours or days?
2. Has anyone tried to mod these by adding two diodes in series with the
power lead on the crystal oscillator? I have seen this "fix" on the web
3. Has anyone found a low cost footprint compatible 30 MHz 5V crystal
oscillator that can be retrofitted?

I greatly dislike operating modules under conditions they are not rated
for (either run at 5V and operate a 3.3V part this way and hope it
doesn't fail or run the module at 3.3V and have lower upper frequency
limit on the AD9850 or AD9851 not to mention incompatibility with
external circuitry running at 5V. So in addition to possible counterfeit
parts and poorly performing or mis-designed filter circuitry, we also
have to worry about omissions in any information about what voltage the
module is designed to operate at.

Caveat Emptor.

"Digital Steve", K1RF


Steven Dick
 

Thank you Alfredo.  Think I’ll order some of these
“Digital Steve”, K1RF
 

Sent: Thursday, January 28, 2016 8:26 AM
Subject: [PHSNA] Re: 3.3V clock oscillators on Type AD9850m and AD9851 modules
 
 

I use thes 30 mhz oscillators:

 
 
They work with 5V an are SMD.
 
I purchased these on arrow.com, they accept paypal.
 
See the datasheet this model have low jitter.
 
If you need the eagle library for this part let me know.
 
Regards.
Alfredo Mendiola Loyola
Lima, Peru
 
This email has been sent from a virus-free computer protected by Avast.
www.avast.com

Miguel Angelo Bartie
 

Hello Steve

I build a  DDS with ad9850 who has 3.3V stamped in the can of the 125MHz clock....then I build a 3.3V power supply for the ad9850 and add 10k resistors in series for  comunication with 5V devices.

73 from py2ohh/ce miguel



Steven Dick
 

I got more curious about what my XTAL oscillators actually are on my Type II AD9850 and AD9851 modules and found this info:

125 MHz oscillator labelled MCO 1510A 125 MHz TQG-9h is a 5 volt oscillator made by Shenzhen Great Electronics. Data sheet:  
 
 
My two 30 MHz oscillators on my two Type II AD9851 boards are labelled CETDCJ 30 032. They are  made by Taiten Electronics. It is a 3.3V oscillator, much to my dismay. One of them already failed. See part numbering guide:
 
http://www.taitien.com.tw/db/download/Model%20Numbering%20Guide_XO.pdf

Dropping the 5V power with 2 diodes and putting series resistors in the comms lines can work, but it's messy. Mosfets made for the purpose of level shifting would be better, but a lot more components as you also need pullups on boith sides, one set goint to the quasi 3.3V and the set near the AD9851 going to +5V.  I think I'll just replace the 30 MHz oscillators with a 5V part, which I have on order.  Replacing should be fun.

"Digital Steve", K1RF