Undervoltage Lockout (UVLO)

This function stops the operation before it malfunctions when a drop in the input power supply voltage or noise occurs in the operating state. Specifically, it turns off the internal MOSFET when the input voltage (Vin) falls below the UVLO threshold voltage. It then turns on the MOSFET if the input voltage rises above the UVLO threshold voltage and enable (EN) remains active.

Left figure: Output (Vout) and PG output Low when the Vin voltage falls below the UVLO threshold voltage
Right figure: When the Vin voltage exceeds the UVLO threshold voltage, the output (Vout) and PG output High.

Overcurrent protection function (OCP) / short circuit protection function (SCP)

Overcurrent protection (OCP) and short circuit protection (SCP) protect components and systems from sudden high currents such as when the output (Vout) is shorted to ground, load malfunction, or system short circuit.

Onsemi's load switch products can change the value of the current applied to the OCP by the value of the external resistor at the OCP pin.

See ONSEMI Application Note AND9848-d.pdf

Thermal protection function (TSD)

When the temperature inside the load switch exceeds the specified thermal shutdown threshold temperature, the power supply and load are disconnected to protect the load. When the temperature drops below the threshold, the switch is turned on.

Backflow prevention function (RCB)

The reverse current prevention function is a function that prevents current from flowing from the output (Vout) to the input (Vin). This prevents current from flowing back from the load to the power supply. The backflow prevention function is especially suitable for USB Type C and Type C power delivery applications.

Discharge function

When the load switch is off, the charge held in the load capacitor is discharged through the internal bleed resistance of this product, so it can be discharged immediately. Also, the slope during discharge can be changed by the resistance value of REXT.

Yellow = EN, Green = Vout, Time Scale = 20ms/div, Y-axis = 1.0V/div
Left figure: REXT=0Ω Right figure: REXT=1KΩ

Equipped with Power Good Pin

Outputs the status when the load switch is fully on. Since this Power Good output can drive the enable of the next device, it is possible to create a start-up sequence with multiple power supplies by combining them. Also, the number of enable signals can be reduced.

Yellow wire = Enable, Green wire = Vout, Blue wire = PG, Time Scale = 200us/div
Left figure: PG outputs High after Vout rises
Right figure: Output Low to PG in Fault state

Adjustable output slew rate function

This is an adjustment function for the rise of the output voltage. When power is applied to the load switch, the capacitor is charged, creating a large inrush current that can damage the system. Therefore, by changing the value of the external capacitor (Csr) attached to the SR pin, the slope of the slew rate can be changed. (Refer to the circuit below)

By adjusting the slope of the slew rate, it is possible to suppress the sudden rise of the output voltage and prevent the inrush current. The figure below is the actual waveform.

Yellow wire = Enable, Green wire = Vout, Time Scale = 1ns/div
Left figure: Csr = OPEN ⇒ SR = 13V/ns
Middle diagram: When Csr = 0.018uF ⇒ SR = 1.7V/ns
Right figure: When Csr = 0.047uF ⇒ SR = 0.66V/ns