I need create negative voltage -700 - -1000mV max current 30mA (typical 5mA) from positive +5 or +3,3V and and all that best in simple and small.
I thing switching capacitor , but small SMD IC have fixed output for example -3,3 or mirrored to the input voltage and I need -700mV ,
My application not simple and dot low power , I need only small negative for tree CMOS op amp and GND must be GND.
> What about a SC voltage inverter plus a negative voltage regulator?
honestly, I do not even know the integrated negative regulator for one volt or less
This is a simple negative polarity charge pump circuit. You may find you can use a 555 IC for the role of both clock and half-bridge. Or perhaps it won't work from a 3.3v supply... then you'll probably need to construct an astable multivibrator.
Use the classic 7660 IC (has been around for decades) in voltage inverting mode, and clamp the output with a series combination of a small signal diode plus a schottky. A 1N4148 and a 1N5711 should work.
Regulated SC voltage inverters are available with -1.2V Vref, e.g. lm27761. You may introduce an intentional offset to the feedback path to get lower output voltage.
Another option, an unregulated SC inverter in combination with one of the very few negative voltage regulators exposing less than -1.2 Vref, e.g. ADP7183.