L5970AD DCDC schematic doubt

[AlexMachine]

Hello,

I am investigating in using L5970AD DCDC converter for a 12VDC to 3V3 need.

It was advised to me by the ST DCDC online simulator.

It's a 20 year old circuit but it it matches the budget, the additional BOM and the efficiency so I am interested.

But I don't reach in answering some questions. If one of you can share some return of experience about this chip I am gladly listening.

I am in design phase, looking datasheets, and except error I don't find my answers :

- The VREF signal is noticed as 3V3. 3V3 is the output I want to create. On the Typical application schematic it seems not clear for me if connecting VREF to the output is okay, or if we need a precursor 3V3 ??? Should we supply a high impedance 3V3 from resistor divided input for example ? I couldn't reach advise about it, the is no paragraph about VREF. Is it an input or an output? What about generating 5V, do we need a 3V3 rail ?

Also, even if switching frequencies are different, why not group L5970AD and L5970D in one unique datasheet ?

Thank you for reading,

A++ Alex

[AlexMachine]

It may be a PGOOD pin for LED

[AlexMachine]

Yes VREF in the air

[Richard Li]

One book "Fundamentals of Power Electronics" is very good.

Author s R. W. Erickson

[AlexMachine]

Depends, because high frequency is more loss in semiC no?

Interesting to separate spectrums from supply EMI and low freq app like audio, to ease filtering.

For L5970 SYNC must be <3V3.

But this 3V3 is the fifth weel of the charette.

PGOOD

What shows the app note?

Regards

[AlexMachine]

Ok thank you for sharing.

Waiting for @Peter BENSCH insight.

Happy to read you

[Peter BENSCH]

No, the mark as Accept as solution was set by yourself, you can also reset it with “Not the Solution”.

[Peter BENSCH]

It's a bit too mixed up for me. Which question is currently open?