I'm driving myself crazy looking for a part I swear that I had found, and even scratched out a block diagram using it... Now I need it, I can't find the part nor the block diagram.
Background: I have several products which have multiple redundant power supplies. I use a shotkky diode from each input to a common positive rail to select between them for my low voltage control (3.3V@500mA). Traditionally, these have all been positive in reference to ground, but I keep getting asked to also support negative rails as a power input. Now I'm doing a board revision I'd like to see about incorporating this.
For reference, these input voltages can be either polarity in reference to circuit (and earth) ground, and range from 10V to 60V away from ground. So +-10-60V. Today I require at least one of the supplies to be positive - this requriement is what I'm trying to eliminate. I've looked at various options, but it seems like the simplest is to add a negative rail and then add an inexpensive charge pump and/or DC DC converter to flip the polarity and then feed it into the buck regulator which is already on the board.
The part I'm going crazy trying to find is the converter I had found which was perfect. Negative input up to at least -70V (for some headroom), inverting, positive output high enough to feed into the 10-60Vin buck converter already on board. And inexpensive. I think it was a switched capacitor inductorless product, but I haven't found any which fit the bill (in particular, high negative voltage), even though I'm almost 100% that I had found one previously. I'm also almost 100% certain this wasn't an isolated product, since isolated usally = expensive transformer.
Does anyone know of a part like I am describing?
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