A low current, negative rail is sometimes required in an optical module for bias purposes. While the relatively low current required helps to keep the size small, there are not many simple and small options for making a negative voltage in a system which has only positive voltages. A simple charge pump may not provide enough output current or output voltage regulation, while a flyback converter is much too complicated and too large to be practical.
However, a wide input voltage buck converter can be used to simply create an inverting buck-boost converter. And when the buck converter used is highly integrated and small, so will the inverting converter be. And when a full test report is available, talk about an easy design!
PMP9760 is a small, simple and efficient voltage inverter reference design that delivers -5V at up to 120 mA from a +5-V source or 80 mA of current from the common 3.3-V input found in optical modules. This is more power than a charge pump delivers and the -5V is well regulated over line and load variations. Adding additional flexibility, the output voltage is adjustable for all types of specific requirements.
Small is the 2 x 2-mm IC with just 5 external components. Simple is the internal loop compensation and the reference design’s documentation. Efficient is the 85-90% efficiency achieved across the load current range. Small, simple, and efficient come together!
How is this a great fit for your optical module or other negative voltage need?