The Maxim Integrated MAX636ACSA+ is a buck regulator that can also run in an inverted topology to generate a negative output rail. It delivers up to 200 mA from a positive input between 2.3 V and 16.5 V, with the output adjustable down to -12 V or fixed at -1.31 V.
Output voltage range — what you can actually get
The output can be set anywhere from -1.31 V down to -12 V, depending on the feedback resistor divider. The fixed -1.31 V option is useful if you just need a small negative bias for an op-amp or a charge-pump reference. The -12 V ceiling is the practical limit for a 16.5 V input rail; if you need a deeper negative rail, this isn't the part.