> 4.2 | Double Regulation

> A second way of solving the problem is to use double regulation. A switched DC/DC converter can be used to convert input voltage >6V to for instance 5V. As a second step a linear regulator can be used to convert 5V to 4V, which can be a suitable voltage level for a GSM module. A linear regulator with a drop out voltage less then 1V must be chosen.
> The advantage with this design is a post filtering effect that lowers the DC/DC converter’s typical output ripple. The disadvantage is the cost and size for having two regulators on board.