A mini-EMP is just a small EMP from either a chemical (NNEMP) or nuclear (NEMP) explosion. For mini-EMPs, potential weapon ranges are detailed in the background document by weapon type:

https://i.imgur.com/xVe90Ka.png

EMPs can occur in a lot of other scenarios too, but these ones can be weaponized specifically to take out telecommunications (like the deep state would during a counter-revolution to take out the Emergency Broadcasting System and public communications), NSA magnetic tape records or the power grid itself.

The effect of small e-bombs has proven to be sufficient for certain terrorist or military operations. Examples of such operations include the destruction of electronic control systems critical to the operation of many ground vehicles and aircraft.

The concept of the explosively pumped flux compression generator for generating a non-nuclear electromagnetic pulse was conceived as early as 1951 by Andrei Sakharov in the Soviet Union, but nations kept work on non-nuclear EMP classified until similar ideas emerged in other nations.