how to simulate "output voltage accuracy" of LDO

[cqmyg5]

Hi,

I found that there's a "output voltage accuracy" item in most LDO datasheet, the value is about 3% or less, I want to know how to get this value by spice simulation.

Thanks!

 

[Mazz]

The answer is linked to the understanding why the regulated voltage varies.
Due to spread (relative and absolute) of LDO components. So you need to use extreme (fast & slow) models to simulate the LDO and Statistical models (montecarlo simulations) defined in your DK.

I hope it can help.
Mazz

 

[cqmyg5]

Re: how to simulate "output voltage accuracy" of L

Thanks Mazz,

Do you mean to simulate the output voltage by varying the SS/FF/SF/FS corner, and then run a monte-carlo simulation?

How about the varied temperature and loading? should I fix the temperature and loading or not?

Finally, how to calculate the percentage?
% = Max(delta_Vout) / Vout

it's right?

 

[kumard35b]

Re: how to simulate "output voltage accuracy" of L

You need to run the corner simulations and note down the Vout..
Keep the Vout which is in the normal condition as reference and note the percentage for fast and slow corners.This will give the output voltage accuracy.

 

[Mazz]

Also temperature has to taken into account.

Put on LDO user side: you need to know in all operating conditions what is the regulated voltage, so on a large population of parts in different ambient condition. The designer needs to identify this and address it.

If you load the regulator or use a different supply voltage, you need to know how much the regulated volage varies, so you have line and load regulation parameters.


I hope it can help.

Mazz

 

[hung_wai_ming@hotmail.com]

For LDO output voltage accuracy, there are basically three specs.
(1) Load regulation: Change of VOUT vs different load
(2) Line regulation: Change of VOUT vs different input voltage variation
(3) Transient output variation: Change of VOUT across transient change of loading.

Of coz, above requires across PVT simulation to get the boundaries. So, above explantions tend to be NOT correct