The design of the analog part of a mixed analog-digital IC for a commercial wireless burglar alarm system is presented as an example of a very low-power VLSI design for battery-operated systems. The main constraint is battery life, which must be at least five years (with standard camera-battery). An operational amplifier, a power supply monitor and an oscillator are the core of the design. The operational amplifier absorbs 1.5 µA while the entire analog part absorbs 4 µA. Measures on each single part show compliance with specification. Test on working environment show its full functionality. Even though the example is application specific, the design solutions and each single element can also be utilized in many other battery-operated low-frequency devices (e.g. environmental parameter monitoring).