#### Use 3.3 volts oscillator with AD9851

Alfredo Mendiola Loyola

Dear All:

Is there a way to convert the output of a 3.3v CMOS oscillator to a 5v ?

I have read that the AD9851 can accept a sinusoidal signal dc biased to Vdd/2.

Can I bias a 3.3 volts cmos oscillator (Square wave) to Vdd/2 to use it with my AD9851 using a VDD of 5 volts?

Regards.

Alfredo Mendiola Loyola

Lima, Peru

Earl Cox, KB5UEW

Many 5V logic chips work with 3V logic Attached is a bi directional logic converter that works well

From: PHSNA@... [mailto:PHSNA@...]
Sent: Monday, December 21, 2015 9:31 AM
To: PHSNA@...
Subject: [PHSNA] Use 3.3 volts oscillator with AD9851

Dear All:

Is there a way to convert the output of a 3.3v CMOS oscillator to a 5v ?

I have read that the AD9851 can accept a sinusoidal signal dc biased to Vdd/2.

Can I bias a 3.3 volts cmos oscillator (Square wave) to Vdd/2 to use it with my AD9851 using a VDD of 5 volts?

Regards.

Alfredo Mendiola Loyola

Lima, Peru

Andy

This question (interfacing between voltage domains) is one I frequently had to deal with.

I have seen ICs (not this one) powered by 5V where all the inputs were compatible with 3.3V or even 2.5V signals ... EXCEPT for the clock input which required a full 5V rail-to-rail swing.  That's not very common, but it can happen.  Always consult the datasheet.

In this case the AD9851 datasheet apparently shows the input must swing between 1.5V and 3.5V at minimum.  So yes, I think you could bias a sine or square wave around 2.5V, and as long as its swing exceeds 2Vp-p, it should work.  Be careful if the source pulsewidth isn't symmetrical.

Become intimately familiar with the datasheet, and if in doubt, consulting an ADI field engineer might be a good idea.

Active converters (amplifiers) are OK but not always needed and IMHO you are better off without them if you don't need them.

Andy