Negative input, positive output buck-boost controller

[owiecc]

I am designing a battery powered gate driver (I need very low C to ground and I will use it only to test the losses of a MOSFET). I decided I will use a Lithium Ion battery as a power source. I will also use this 3.7V voltage as negative gate voltage. So now I need to convert a 3.7V to the "on" voltage so I can control my MOSFET with -3.7/15V.

Using negative battery terminal as reference I can boost the voltage to whatever I want + 3.7V. But then whenever my battery voltage drops my positive output gate voltage will change as well. I want this voltage to be constant and controllable.

I thought I can make a buck/boost and convert my -3.7V to e.g. +15. Do you know any good, simple controller that can do it? LT has LT8302 but it does not accept my input voltage. Controller should work down to lets say -3.3V. The less external components the better. UVLO would be perfect. Signaling UV would be even better.

[tszaboo]

Inst it easter to make a boost converter and make 18V than use the battery and invert the voltage?  Do you really need that negative rail? Usually I discourage voltage inverting, because it is a messy business.
Also, If you are making a one-off circuit, cant you just take two 9V batteries and put them in series?

[owiecc]

I explained why I don't want to boost in the second paragraph. My positive voltage becomes battery voltage dependent.

I may need to make few of these later on so powering them from a single battery will be very easy. If I need two or three batteries per MOSFET it will be a pain to handle that.

I have actually been tricked by the app note. LT8302 has an input voltage range of 2.8–40V. I will try to do do the circuit with it.

[KX36]

There are non-inverting DC-DC converters which allow voltage above and below input, if that's something you prefer. There's the SEPIC, or even simpler is the flyback which is just a buck-boost with separate input and output windings to the inductor so that polarity doesn't have to be inverted. Almost any generic PWM controller will run any of these basic topologies if you set them up correctly. The MC34063 used in EEVblog #110 has example circuits in the datasheet for buck, boost and buck-boost, as well as a step by step guide to component selection and you could use that if you like.

[owiecc]

Anybody know whats with the wide price variation, from $8.56 to $21.07?

M may be for military spec.