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Why can the integrated load switch Load Switch replace the discrete power MOS switch in many fields

Published:2022.01.17 Type:Product Information Share:


In recent years, many smart wearable devices, TWS earphones, NB-IOT, SSD and other products have used a large number of integrated load switches to replace discrete power MOS switches. This is because integrated load switches have discrete power MOS switches. Incomparable advantages. A brief comparison of discrete power MOS switches and integrated load switches is given below.

01

Single PMOS

The circuit of a single PMOS and the waveform at the moment when the switch is turned on are as follows: When ON is pulled low and the voltage difference between ON and VIN is much lower than the VTH of the PMOS, the PMOS will be turned on.

   该电路特点如下:

   •单个器件,电路简单成本低

   •存在浪涌电流,导致输入电压瞬间拉低

   •输入电压最大值取决于MOS的VGS和BVDSS

02

PMOS+NMOS

The circuit of PMOS+NMOS and the waveform at the moment when the switch is turned on are as follows: when ON is pulled high, the NMOS will be turned on, so that the gate of the PMOS will be pulled down, and the PMOS will be turned on.

The circuit features are as follows:
     • The maximum input voltage depends on the VGS and BVDSS of the MOS
   • There is an inrush current that causes the input voltage to momentarily pull down
    • There is leakage current, leakage current path: VIN->resistor->MOS->GND

03

PMOS+NMOS

+Capacitance

The circuit features are as follows:
    • Inrush current is controlled
    • There is a negative voltage on the output voltage
   • When the input voltage is powered on, there will be a short turn-on, resulting in a surge current
   • There is leakage current, leakage current path: VIN->resistor->MOS->GND

04

PMOS+BJT

+Capacitance

According to the PMOS+NMOS+capacitor mode, the further improved PMOS+BJT+capacitor structure and the instantaneous waveform of the switch are as follows:

    该电路特点如下:

   •浪涌电流得以减小,但仍存在非线性浪涌电流 

   •存在漏电流,漏电流路径:VIN->电阻->BJT->GND

05

Load Switch

The circuit of the integrated load switch and the waveform at the moment when the switch is turned on are shown in the figure below: The load switch is highly integrated and the application circuit complexity is reduced.

The circuit features are as follows:
    • Inrush current is controlled
    • Few peripheral components, small size
    • Wide input voltage range
    • Small leakage current
    •It is easy to integrate more protection functions as needed, such as: short-circuit protection, over-temperature protection, output rapid discharge control, etc.



Data comparison

The following is the comparison data using the integrated load switch and the discrete power MOS switch (based on the PMOS+BJT+capacitor structure):

The table shows the many advantages of the integrated load switch, in fact there are many other functions in addition to the following functions. If various functions are added to the discrete power MOS switch, a large number of peripheral circuits must be added (which will increase the BOM, board size and cost), which is obviously not an optimal solution.



Summarize

In a broad sense, the integrated load switch can replace the discrete power MOS switch, enabling the terminal product to achieve smaller size and better battery life, optimize the circuit design structure, and achieve more functional integration.

In terms of the market, the large share of MOS switches is mainly occupied by overseas manufacturers, so there is huge room for domestic substitution. And in actual application, Load Switch is more popular with engineers because of its "small and complete" characteristics, and has realized the replacement of discrete power MOS switches in more and more application fields.




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