What this ORing controller does for your power rail
The LM74700MDDFREP is an N+1 ORing controller from Texas Instruments, designed to replace a Schottky diode with a low-Rds(on) N-channel MOSFET in redundant power-supply architectures. It handles a supply range of 3.2V to 65V, covering 12V, 24V, and 48V rails without external pre-regulation. The controller draws 80 µA typical supply current, which keeps standby loss low in always-on ORing applications such as base-station power feeds or industrial PLC backplanes.
Switching speed and fault response
The ON delay is 1.4 µs and the OFF delay is 450 ns. The fast turn-off limits reverse current during a supply fault or short, reducing stress on the upstream MOSFET and downstream load. Because the controller does not integrate the power switch, the designer selects the external N-channel FET based on the load current and thermal budget. The 1:1 input-to-output ratio simplifies the control loop for single-channel ORing.
The device is supplied in an SOT-23-8 package with a TSOT-23-8 supplier device package. The small body fits tight layouts, but the thermal pad is absent — the junction-to-ambient thermal resistance relies on the copper area on the PCB around the pins. Surface-mount assembly is standard; the tape-and-reel option supports automated pick-and-place for volume production.