batteries - How to regulate a 3.6 V battery to two power rails (3.3 V and 1.8 V)?

I have a 3.6 V battery from which I need two voltage rails, one that is 3.3 V and one that is 1.8 V. How should I design this circuit such that it is the most power efficient?

Here is what I was thinking:

• Using one voltage regulator to regulate the 3.6 V down to 3.3 V, and using voltage division after the 3.3 V to create a 1.8 V


• Using two voltage regulators to regulate the 3.6 V down to 3.3 V and 1.8 V

Are either of these good options? What else might you suggest?

Follow-up question about using two regulators: Should I put them in series or parallel?

i.e.

Series: Regulate 3.6 V down to 3.3 V, and then regulate this 3.3 V down to 1.8 V.

Parallel: Regulate 3.6 V down to 3.3 V, and separately regulate 3.6 V down to 1.8 V.

^{simulate this circuit – Schematic created using CircuitLab}