The European Spallation Source (ESS) is a planned neutron source to be built in Lund, Sweden, which is planned to produce the first neutrons in 2019. It will have an average beam power at the target of 5 MW, an average current along the linac of 50 mA, and a pulse repetition rate and length of 20 Hz and 2.86 ms, respectively. The linac will have around 200 LLRF stations employed to control a variety of RF cavities such as RFQ, DTL, spoke and elliptical superconducting cavities. The challenges on LLRF systems are mainly the high demands on energy efficiency on all parts of the facility, an operational goal of 95% availability of the facility and a comparably short time from start of final design to commissioning. Running with long pulses, high current and spoke cavities also brings new challenges on LLRF design. In this paper we will describe the consequences these challenges have on the LLRF system, and the proposed solutions and development projects that have started in order to reach these demands.