App note: Analog switch lowers relay power consumption

an_maxim_AN956

Clever way of starting-up relays discussed in this app note from Maxim Integrated. Link here

Relays are often used as electrically controlled switches. Unlike transistors, their switch contacts are electrically isolated from the control input. On the other hand, the power dissipation in a relay coil may be unattractive for battery-operated applications. You can lower this dissipation by adding an analog switch that allows the relay to operate at a lower voltage.

App note: Multiplex boosted class-D without additional external circuitry

an_maxim_an5792

An analog switch MAX14689 from MAXIM Integrated let signals that are higher than rail voltage pass. Link here (PDF)

Boosted class-D amplifiers drive speakers with voltages greater than the supply voltage. These amplifiers are becoming more common because they allow higher performance audio from a single lithium ion battery. Most boosted class-D amplifiers, however, do not give the user access to the internal boosted voltage. This makes it difficult to multiplex a speaker to multiple audio sources using common analog switches. This application note discusses how the Beyond-the-Rails capability of the MAX14689 allows it to switch these signals without additional circuitry.