Fan-speed controllers can be very handy when you have a system which is dissipating a lot of power, but is also built into some kind of enclosure. This makes forced-cooling with a fan a necessity. If you would like to make the control of this fan dependent on the temperature, but don’t want to delegate this task to the existing microcontroller, then a separate control IC will be very useful. This month: MIC502 and MAX6643.