I am considering using ADS1258 - a bipolar ADC. It needs an external reference across REFP(+) and REFN(-). How do I generate precise -2.5V assuming I have +12V and -12V analog voltage rails? I can generate an approximate -2.5V using something like LM337 but I need something more accurate as that voltage is going to be used as a reference. A more precise way is to use a low input offset voltage opamp to invert a positive reference but that would still add some error.
What is the standard way to get good quality bipolar reference voltage in a circuit?