Input protection switch has true reverse blocking to protect internal circuitry

23rd July 2018
Posted By : Caroline Hayes
Input protection switch has true reverse blocking to protect internal circuitry

 

Providing over-voltage protection for Type-C Power Delivery applications, the AOZ1376 is a smart protection switch from Alpha and Omega Semiconductor (AOS).

It has true reverse blocking and is Type-C Power Delivery (PD)-compliant, with up to 28V over-voltage protection.  The switch has an reverse current blocking capability for applications where internal circuitry requires protection from exposure to high voltages. RDS on is 20mΩ.

The switch is supplied in a thermally enhanced 3.0 x 3.0mm DFN package, developed using the company’s co-packaging technology, which combines an IC with protection features and SOA MOSFET. The switch can be used in notebooks, ultrabooks, dongles, and docking stations, with Thunderbolt/USB Type-C PD ports.

Typically, USB Type-C sinking applications are protected from a reverse current using a circuit that uses two discrete back-to-back MOSFETs with resistors and capacitors to provide basic soft start functionality but without programmability and protection features. The switch overcomes these disadvantages, says the company, saving both component count and PCB footprint while offering a robust protection feature set to increase the reliability of end products using Type-C PD. 

“The thinner profile, higher power and greater flexibility offered by USB Type-C and USB PD 3.0 standards have prompted many computer manufacturers to drop the barrel jack in favour of USB Type-C ports for charging their notebook and ultra book offerings; and for the best user experience many of these devices allow the laptop to charge from any of the USB Type-C ports. This makes reverse voltage protection imperative for these devices,” said Mehdy Khotan, power IC marketing director at AOS. “AOZ1376 is used in the Type-C charging path of such devices. It not only protects the laptop and its battery from over-voltage and over-current, but it also prevents an unintended reverse current and over voltage on the opposite port, protecting the laptop’s peripheral devices.”

The switch operates from 3.4 to 22V on Vin. Both Vin and Vout are rated at 28V absolute maximum. The back-to-back switch configuration blocks any current flow between Vin and Vout pins when the device is disabled or when the device is enabled, but Vout is greater than Vin.

There is a programmable soft start and protection against short-circuit, thermal overload, reverse voltage and over-voltage.  The over-voltage protection threshold is selectable by an external resistor. The internal soft-start circuitry controls the inrush current due to highly capacitive loads, and the slew rate can be adjusted using an external capacitor. The device also features robust ESD of ±8kV on Vin and Vout pins and ±4kV on all other pins.

The switch is available now in production quantities with a lead-time of 12 weeks.


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