Fixed output LDOs offer precise output voltages and simplified circuitry with the caveat of the application having to accept that voltage. Variable regulators offer the freedom to custom-tailor the voltage needed for a design, but require additional components. It is good practice to get the output voltage as close as possible to the circuit requirements. The following formula is used to calculate the output voltage when R1 and R2 are selected for an adjustable LDO: Vout=(1+ R1/R2)Vref. As a general design rule, the current rating of the device should be 20% more than the required load in order to account for less than ideal conditions, current spikes, etc. Keep in mind that high current devices will often come in a larger package in order to handle the dissipated heat. Depending on PC board space, capabilities, and specified requirements, the type of package will need to be determined. Through-hole components offer ease of use and effortless ability to be reworked. Surface mount, on the other hand, saves space and allows for more components to be placed on the board as the opposing side is now free.