Size of text field in module's config form in back-end , presta 1.6

[Trampino]

Hello, can anybody tell me, how can I set size and number of accesible letters in text field in config form of my module?

I tried this.

'size'=>15,

But without any effect.

 

I tried to find some solution in presta forum and google, but no success. May be I set my search request bad.

 

Is there any possibility to set legth of text field and maximal number of letters which administrator can write to text field?

 

Thanks a lot for your answers.