Power Multiplexers
Power multiplexers (power mux ICs) are devices that provide for seamless switching between two or three power supplies. These can switch power rail sources, or intelligently switch power sources for powered interface standards. They are used in applications like computers, digital cameras, modems, cellphones and MP3 players. They are also found in battery management systems and in peripheral power interface systems like Thunderbolt, Power over Ethernet (PoE) and USB.Power multiplexers can also be referred to as power distribution switches. They are designed to switch between input power supplies so as to provide a continuous output supply rail. They usually do this by controlling very low on-resistance MOSFET switches. MOSFETs have high off isolation, which is important to prevent back-feeding power between the two inputs. They typically incorporate both an N and P channel MOSFET, a charge pump for pulling gate voltage above the source and a driver for controlling the gate voltage. An enable input switches between sources. They typically incorporate thermal protection and under-voltage lockout. Under-voltage lockout is used in systems to allow for hot insertion.Thunderbolt power multiplexers may include current limiting. They also include the ability to interface to different voltage levels as required by Thunderbolt. This includes the high voltage (VHV) 4.5V to 19.8V supply and the low voltage (V3P3) 3V to 3.6V power supply. They will detect when the high voltage supply is present when the high voltage enable pin is enabled and wait for a reverse current to be detected in the low voltage switch before turning it off. This guarantees smooth transition with the minimum of supply droop or shoot-through current. When switching from VHV to V3P3 the VHV will be disabled, and the output voltage monitored until it discharges to 3.3 volts before enabling the V3P3 rail. This also minimizes transition spikes.Shop Arrow.com’s selection of power multiplexers, including auto switching power muxes and 1.5V to 5.5 power multiplexers. 더 읽기 읽기 안 함