ZHCSCK8G May 2014 – October 2017 LP8860-Q1
PRODUCTION DATA.
There are two main considerations when choosing an inductor; the inductor must not saturate, and the inductor current ripple must be small enough to achieve the desired output voltage ripple. Different saturation current rating specifications are followed by different manufacturers so attention must be given to details. Saturation current ratings are typically specified at 25°C. However, ratings at the maximum ambient temperature of application should be requested from the manufacturer. Shielded inductors radiate less noise and are preferable. The saturation current must be greater than the sum of the maximum load current and the worst case average-to-peak inductor current. The equation below shows the worst case conditions.
where
As a result the inductor must be selected according to the ISAT. A more conservative and recommended approach is to choose an inductor that has a saturation current rating greater than the maximum switch current limit defined by <BOOST_IMAX_SEL[2:1]> EEPROM bits. A 22-µH to 33-µH inductor with a saturation current rating of at least 9 A is recommended for most applications. The inductor resistance must be less than 300 mΩ for good efficiency. See detailed information in Texas Instruments Application Note Understanding Boost Power Stages in Switch Mode Power Supplies (SLVA061). “Power Stage Designer™ Tools” can be used for the boost calculation: http://www.ti.com/tool/powerstage-designer.