True shutdown ldo's, buck converters

Hello Adam,
Thanks for the post.

We need a little more information to route your request properly.

1. Vin range, minimum and maximum
2. Is isolation required from Vin to Vout
3. 1Amp output, is this a dual output, both 12 and 15V, or is it a single selectable output
4. You have a shutdown signal that can be applied to the converter, or does it need to go to sleep by itself and stay low Iq while sleeping.
5. Any other details would be helpful

Thank you for fast response!

Regarding questions:

1. Vin: from 15V(max, could be lower) to 22V(min, could be higher)

2. Not required

3. 1A single output. By 15V/12V I ment this or this. 15V would be perfect, if there is no part with 15V output then 12V one can be an alternative.

4.  Yes, I have shutdown signal. However if there is solution when IC goes sleep itself when no load detected then I'm interested.

5. I would like to go for the simplest solution possible. Because it is auxiliary supply to be turned on only if there is an foult in the system. So I hope never :) If smps then with internal FETs preferably. PCB space is requirement here. 

Regards,

Adam

Hi Adam,

What is the time duration of the operation of this circuit? This determines whether or not a smaller circuit can do the job.

If your Vout is always smaller than Vin, then you just need a buck.  If you Vout can be higher or lower than Vin, then you need a buck-boost type.  Please confirm the Vin and Vout conditions. 

Thanks,

Youhao Xi, Applications Engineering 

Time duration?

Tricky question...

Can you propose circuit for 10s and another for 1 minute?

Output always lower than input.

Only buck? Is there maybe some linear regulator?

Thanks,

Adam

Hi Adam,

If you output is always lower than the input, you should consider the buck topology.  Let me forward this to our buck group.

By the way, either 10s or 1m is considered a dc condition for the switch mode dc-dc converter which usually operates above a few hundred kHz.

Thanks,

Youhao