Ideal diode protection switch for Type-C Power Delivery

Ideal diode protection switch for Type-C Power Delivery

There are two: AOZ13984DI-02 and AOZ13987DI-02, both in 3 x 3mm thermally-enhanced DFN packaging, designed to be used in devices that are charged through a USB connector, to prevent current flowing back out of the device through the Vbus pin.

Inside is a control IC co-packaged with back-to-back mosfets, and reverse current under fault conditions can be blocked while working at up to 22V.

The differences are:

  • AOZ13984DI-02: 33mΩ typical on-resistance, 5.5A continuous sink, 15A peak (10ms 2% duty)
  • AOZ13987DI-02: 20mΩ typical on-resistance, 8A continuous sink, 20A peak (10ms 2% duty)

In both cases, normal operation is over 3.4 to 22V (28V abs max) and -40 to +125°C junction (thermal resistance is 2.8°C/W θjc and 36°C/W θja).

Ideal diode protection switch for Type-C Power DeliveryIn the case of the 20mΩ AOZ13987, when the IC is enabled, it regulates Vout to be 35mV less than Vin from no-load, through medium load and up to the point that the mosfets saturate to 20mΩ. After this, the voltage across the mosfets is determined by load current. The 33mΩ AOZ13984 instead works on 70mV.

If for any reason Vout increases such that Vin – Vout is <35mV, it is assumed that current is about to be forced back through the IC and the gate driver forces the switch to turn off.

A fast comparator also turns off the power switch if Vout – Vin is higher than 50mV after a delay time. And when it is first enabled, or during auto-restart, the power switch will be kept off if Vout is 50mV higher than Vin, according to the data sheets.

The switch is also turned off when the die reaches 140°C, after which it can only be re-enabled by either toggling the enable pin or cycling the input power supply.

Soft-on is implemented, so when device is enabled thorough its enable pin, the mosfet gates are controlled to ramp the output up linearly until Vout reaches Vin at a rate set by an external capacitor.

 

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