It highly depends on the specs you wish achieve. In general, it is possible to design very low-voltage BGRs, even below 1.2V (you can have a look on IEEExplorer). In this case of course the reference voltage would be smaller than the usual value (i.e., 1.12V).


SATurn

The theoritical minimum headroom for current mode bandgap can goes down to vbe+vdssat which can be lower than 1 V. However, as the voltage goes lower, I found it harder to achieve good accuracy.

Regards,
Chase

Hi:jim
      I have design 0.13um bandgap, and the output voltage is 0.525v, the chip's  performance have some problem , you should be care the start up circuit 's margin, otherwise the bandgap should not be start normal, other parameter is ok, 1V-1.4v: variable 4mv and temp 0-85c : about 3mv.

Have you considered doing a 1.2V output BG (flattest thermal response) and using the I/O transistors? Also, if you dont have the 1.6V (give or take) to run that, you can use charge pumping to create it internally.