Bandgap reference Trimming

[banosey]

hi all,
I am designing a bgr circuit and due to process variations across corners a sort of trimming should be done.
I need some papers about trimming helping me in my design.
can any one help?
thanks in advance.

banosey

 

[cesczhang]

you can trim the resistors, its depends on your trim range, and the trim bit you can afford

 

[dick_freebird]

I can't recall seeing any papers about trimming, I think it's
not the sort of "academic" thing that favors publication. More
of a grimy trick to get something manufacturable.

You will need at least to trim tempco and then trim voltage.
One affects the other.

There are schemes that offer more freedom, basically

temp sensor -> ADC -> cal-map -> trim-codes.

You'll see some pretty nice flat performance out of that, but
it entails a lot more design and test time.

Manufacturers of precision references, especially the old
school ones, might have some app notes / tech briefs
that give you the gist of it.

Before you get too excited about trimming, check what sort
of nonvolatile (preferably one-time-programmable, if you are
shipping product) bit memory you have. Fuse, antifuse,
EEPROM? If you don't have that, you're looking at few and
not too pleasant options.

 

[banosey]

thanks all

 

[love_analog]

dick,
What do we typically trim first. I thought we typically trim the reference first and then the tempco. tempco would effect the reference but not vice-versa.
Also can't we use poly fuses instead of NVM?

 

[checkmate]

If your output is not 1.23V (which is most often the case), then just trim for tempco, followed by output voltage.