If you're talking about a bang-bang, switched current source
triangle wave (or sawtooth) oscillator, I have had best luck
with (1/3) / (2/3) resistor dividers as low and high "references"
(like the old NE555). If you make the charge, discharge current
-and- the trip thresholds all supply ratiometric, that's pretty
good.
Alternatively you could make the charge / discharge current
fixed, and make the threshold points fixed as well (like, take
the oscillator output through 2 dividers, both of which are
compared against vref, yielding two different and constant-
spaced switchpoints from a single reference).
Triangle wave is easier than sawtooth as the discharge
stroke of the sawtooth oscillator will have strong temperature
and supply variation, even if the slow charge ramp is made
quasi-constant. I've made triangle wave PWM oscillators
that are near dead flat with temp and supply good past
5MHz in 0.5um CMOS, all switched-resistor and comparators
(and SRFF).