More than 90% of hardware engineers will encounter problems when MOS tubes are burned out!

MOS The tube burned out , I Believe 90% The above hardware engineers will encounter such problems in their career . However, such problems are always impossible to prevent . So today Xiaobai will explain to you MOS Several common causes of tube burning .

Before the presentation , Xiaobai draws it for everyone MOS The equivalent model of the tube ( With what I am most familiar with N-MOS Tube example ).

I'd like to introduce some nouns that you must master
VDSS: The maximum voltage applied between the drain and the source .
VGSS: The maximum voltage that can be applied between the grid and the source .
IDC: The maximum DC current allowed by the drain .
Tch:MOS Upper limit temperature of pipe channel
thermal resistance ： Indicates the difficulty of heat conduction , The smaller the thermal resistance value , The better the heat dissipation performance .
IDSS: Leakage current between drain and source .VGS=0 when ,D And S In between VDSS
IGSS: Leakage current between grid and source .VDS=0 when ,G And S In between VGSS.
RDS(on)： Drain electrode / Conduction impedance between sources .MOS The impedance of the tube in the on state . The greater the conduction impedance , The greater the loss when opening . Therefore, this participation should be as small as possible . RDS(on)=VDS/ID.

MOD There are four main reasons for tube burning

1. Overvoltage ：VDS,VGS Too big , Not designed in strict accordance with the standard format , It exceeds its own rated voltage , And reach the breakdown voltage .

2. Over current ： Continuous high current or instantaneous high current , More than the MOS The maximum value that can be borne .

3. Static electricity ：MOS Tube belongs to ESD Sensitive devices . Its input impedance is very high , In addition, there is junction capacitance , Therefore, if there is electromagnetic field or electrostatic interference outside , Will accumulate charge . When the charge accumulates to a certain extent , An increase in voltage will cause tube damage . At the same time, it is difficult to discharge static electricity in places with strong static electricity , Easy to puncture . An instantaneous rise in voltage will bring a short high current ,MOS The amount of heat produced by heating is punctured and burnt out before it can dissipate heat .

4. Heat damage ： Because more than SOA Caused by heating in the safe area . The causes of heating are mainly divided into DC power and transient power .

DC power reason ： On resistance RDS(on) loss （ The resistance will increase at high temperature , Under a certain current , Generate too much heat ）
By leakage current IDSS The resulting power consumption

Transient power causes ： The load is short circuited .
Switching loss

All in all MOS There are many reasons for the tube burning , Here are some things I know , If you have encountered other situations , Welcome to the comments area to add .