A 1.5 volts Bandgap Reference

[harry_the_elecwhiz]

I am trying to build a Bandgap reference with temp independent supply of 1.5 volts.
i have been successful in building a 1.25 volts bandgap reference.

does anybody have suggestions on design techniques ?

Have any of you designed a 1.5 volt Bandgap before ??

 

[dick_freebird]

You want to use a feedback network driven by your output
stage, resistor division to get the 1.25(ish) feedback voltage
and take your output from the top of the ladder.

 

[harry_the_elecwhiz]

My process limits my supplies to +/- 1 volts.
I am hence using a charge pump to provide a 3 V supply for VDD of the Bandgap.
I have a start up circuit using my normal supply of + 1 VDD

the +3 volt supply that is generated is used for the BJT paths and the VDD of the Op Amp which inturn drives a level shifter

I understand the idea of using a resistor string to feedback 1.25 which is what i am trying now.

could you tell me what are the components i can tweak to reduce positive PTAT. similarly wat needs to be tweaked for increasing neg PTAT. I think that would really help.

 

[baenisch]

Hi

For 1.5V supply I would not use the classical bandgap approach
The classical approach will show some serious problems in
the low-temp/slow corners, especially during startup ...
Look out for some papers about low voltage bandgaps. The
basic idea there is, that you add a ptat and an iptat current.
THis current is injected into a resistor, allowing an very easy
voltage level trimming. Such a architecture works find down
to ~ 1V. As a nice addon you can also easily trim the temperature
coefficients of ptat and iptat. Pumping the supply might yield in some
problems with ac stability if not probably filtered.

Best Regards

Andi