VFC32: VFC32

O I FORGOT THE VOLTAGE CONTROL WILL BE FROM A SERIES 

RECISION VOLTAGE REF DEVICE AND THE VOLTAGE WILL BE DRIVEN

WITH A OP-AMP TO THE VFC32 FOR A MORE STABLE VOLTAGE OVER

TEMP AND TIME

Hi Willie,

Thanks for your post. Our engineer responsible for this device is out of office on Holiday break. Please excuse the delay, we will support you soon.

Hi Willie,

what do you mean by 400Hz? Full scale frequency?

Kai

YES I WOULD LIKE TO ADJ THE DC VOLTAGE TO THE PART SO SO I GET A 400HZ SQ. WAVE OUT OF THE PART

I WILL BE USEING A VOLTAGE REF  AS THE ADJ VOLTAGE  SO THE OUTPUT STAYS STABLE OVER TEMP AND TIME

Hi Willie,

For C2 take a cap with very low dielectric absorption:

This table can be found here:

I would take a PS cap like this one:

Or an encapsulated PP cap like this one:

For C2 only the dielectric absorption and the leakage current is of interest. Then PS and PP is the best dielectric material and the true film types should be favoured over the metallized film types.

But when it comes to temperature drift and long term drift C0G(NP0) should be prefered:

So for C1 I would choose a C0G(NP0) cap, best with low manufacturing tolerance.

Later more...

Kai

Hi Willie,

figure 2 of datasheet of VFC32 shows what cap values have to be chosen, if you want to reduce the full scale frequency down to 1kHz or even below. However, this will result in cap values which might be unsuitedly large and difficult to obtain.

A remedy is to add a digital frequency divider to the output of VFC32. You could take the CD4024 which has a Schmitt trigger clock input. The CD4024 is fast enough to be able to handle the frequencies of interest but is, at the same time, slow enough to keep the switching noise low.

Kai

OKAY I'VE FIGURED IT OUT NOW ,NOW I SEE  HOW THE PART WORKS ,WHICH IS MUCH BETTER THAN THE OTHER VF-FV CONVERTER ICS OUT THERE 

THANKS 

YOU CAN CLOSE THE CASE