New Industry Products

Alpha And Omega Semiconductor Unveils USB-C Power Delivery Source Protection Switch

February 12, 2021 by Gary Elinoff

The tiny new smart protection switch operates over a 3.4 to 23-volt range and features a 36mΩ ON-Resistance

The AOZ1374DI from  Alpha And Omega Semiconductor (AOS) is a multi-featured current-limiting protection switch. Both the VIN and VOUT are rated at an absolute maximum of 28 volts. To limit the inrush current when powering high capacitive loads, the device features soft-start capability that the user can program up to a time limit of 10ms. During shutdown conditions, the supply current reduces to 5µA.


Typical application for the AOZ1374DI
Typical application for the AOZ1374DI. Image courtesy of AOS’ datasheet.


A “Smart” Protection Switch

AOZ1374DI offers what AOS describes as “true reverse current blocking” (TRCB) protection. This feature serves to prevent unwanted reverse-current from VOUT to VIN. Another capability is internal current-limiting circuitry that will, conversely, protect the supply from large load current. The current limit threshold is user-controllable via an external resistor. 


System Details

The device features the following fault protections:

  • Input Under-Voltage Lock Out (UVLO)
  • Input Over-Voltage Protection (OVP)
  • Short-Circuit Protection (SCP)
  • Thermal Shutdown Protection (TSD)


Over Voltage Protection Level

The input OVP level can be set by the user and is thus can be referred to as programmable over voltage protection POPV. As indicated in the “typical application” diagram, its threshold can be set via resistor network from VIN to ground.


Turning the AOZ1374DI On and Off

This can be done via the EN pin. Alternatively, the EN pin can be employed to cause the device’s operational state to be governed by the VIN value. This, too, is achieved via a resistor network.

The Current Limiting Threshold can be set from 0.75 to 3.56  amp by varying RLIM over a range of 8.25  to 1.74 kΩ.


Exposed Thermal Pad

One of the reasons that such a small device can handle so much power is its Exposed Thermal Pad, referred to as the EXP pin. For best effect, it must be soldered to a metal surface directly below itself, and that metal surface must be connected to system ground through as many copper VIAs as practicable.


Two Versions

AOZ1374DI-02 will turn the smart protection switch off when a fault condition is detected. The unit can only be restarted via a signal sent through the unit’s EN pin.

AOZ1374DI-01, on the other hand, will restart automatically if and when the detected fault clears. 

As per Peter Cheng, Power IC Senior Marketing Director at AOS, “The thinner profile, higher power, and greater flexibility offered by USB Type-C and USB PD 3.0 standards have prompted many to simplify the connectivity between devices down to a single wire for both power and data. Mr. Cheng goes on to state that the “AOZ1374 high voltage capability provides the most compact and simple protection device for charging or powering high-power external devices.”



  • USB power delivery source switch
  • Portable devices
  • Desktops 
  • Smartphones and tablets
  • Notebooks and ultra-books


Physical Considerations

  • The device is available in a 3 by 3 mm 10-pin DFN package
  • Operating temperature range is from -40 to + 125 °C 


Safety Features

  • Human Body Model  (HBM) ESD rating is ±4 k V on all pins.
  • Charged Device Model (CDM)  ESD rating: ±1 k 
  • Conforms to IEC 61000-4-2 to ±8 kV on VOUT 
  • IEC 61000-4-5 surge immunity to 45 V on VOUT, no cap 
  • IEC 62368-1: 2014 E326264-A6008-CB-1 


Environmental Concerns

The new smart protection switch is RoHS compliant.