Controller Drives PFETs for Low-loss ORing

Aug 24, 2005 12:40 PM

Linear Technology’s LTC4414 is a robust "ideal diode" PowerPath controller for driving large PFETs with substantial gate capacitance. The LTC4414 permits low-loss ORing of multiple input dc power sources. The 20-mV forward voltage across the MOSFET is at least 10 times lower than that of a Schottky diode. As a result, the device increases efficiency by an order of magnitude because of the PFET’s lower power loss and self-heating.

The LTC4414 is guaranteed to meet performance specifications over a wide range of user conditions, including an ambient temperature range of -40°C to 125°C and operating voltage range of 3 V to 36 V. The LTC4414 also provides reverse-battery, overcurrent and MOSFET protection circuitry in a 3-mm × 3-mm, 8-lead MSOP package. In addition, the device offers a digital control input and an open-drain status output pin to simplify interfacing to a microcontroller. Applications include systems that typically take power from multiple input sources, such as high-current power path switches, UPSs and back-up battery systems.

Multiple LTC4414 devices can be used to enable switchover between multiple batteries or charging of multiple batteries from a single charger. The LTC4414 status pin can be used to control a second P-channel MOSFET power switch so that both Schottky diodes are eliminated from the diode-OR circuit. The IC's 30-µA quiescent current is independent of the load current. In addition, the LTC4414 uses a strong gate drive for gate turn-on and turn-off times of 600 µs and 20 µs, respectively. The LTC4414 is priced starting at $1.85 each in quantities of 1000.

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