MOSFET data sheet, try looking at it this way!

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MOSFET data sheet, try looking at it this way! [Copy link]

There are many relevant parameters in the MOS tube data sheet. Taking the MOS tube VBZM7N60 as an example, let’s take a look at what parameters the MOS tube data sheet generally includes.

The limit parameters are also called absolute maximum rated parameters. During the use of the MOS tube, the limit parameters shown in the figure below must not be exceeded under any circumstances, otherwise the MOS tube may be damaged .

V _DS represents the maximum voltage that can be applied between the drain and source.

V _GS represents the maximum voltage that can be applied between the gate and the source.

ID _represents the continuous current value that the drain can withstand. If the current flowing exceeds this value, there is a risk of breakdown.

I _DM represents the single pulse current intensity that the drain-source can withstand. If this value is exceeded, there will be a risk of breakdown.

EAS stands for single pulse avalanche breakdown energy. If the voltage overshoot value ₍ usually caused by leakage current and stray inductance) does not exceed the breakdown voltage, the device will not undergo avalanche breakdown, so there is no need to dissipate the avalanche breakdown capability. _EAS specifies the level of reverse avalanche breakdown energy that the device can safely absorb.

PD stands for maximum dissipated power, which refers to the maximum drain-source dissipated power allowed when the MOS performance does not deteriorate. When using it _, please note that the actual power consumption of the MOS should be less than this parameter and leave a certain margin. This parameter will generally decrease with the increase of junction temperature. (This parameter is unreliable)

T _J , T _stg , these two parameters calibrate the junction temperature range allowed by the device's working and storage environment. This temperature should be avoided and a certain margin should be left. If the device is ensured to work within this temperature range, its working life will be greatly extended.

dV/dt reflects the device's ability to withstand the rate of voltage change, the larger the better. For the system, too high dv/dt will inevitably bring high voltage spikes and poor EMI characteristics, but the rate of change can be corrected through the system circuit.

Thermal resistance indicates the difficulty of heat conduction. Thermal resistance is divided into thermal resistance between channel and environment and thermal resistance between channel and package. The smaller the thermal resistance, the better the heat dissipation performance .

△V _DS /T _J represents the temperature coefficient of the drain-source breakdown voltage, a positive temperature coefficient. The smaller the value, the better the stability.

V _GS(th) represents the turn-on voltage (threshold voltage) of MOS. For NMOS, when the external gate control voltage V _GS exceeds V _GS(th) , NMOS will be turned on.

I _GSS represents the gate drive leakage current. The smaller the better, it has a smaller impact on system efficiency.

I _DSS represents the drain-source leakage current, which is the drain-source leakage current when the gate voltage V _GS = 0 and V _{DS is a certain value, generally in the microampere level.}

R _DS(ON) represents the on-resistance of MOS. Generally speaking, the smaller the on-resistance, the better. It determines the conduction loss of MOS. The larger the on-resistance, the greater the loss and the higher the temperature rise of MOS. In high-power power supplies, the conduction loss will account for a large proportion of the total loss of MOS.

gfs stands for forward transconductance, which reflects the ability of the gate voltage to control the drain-source current. If _{gfs is too small, the MOSFET turn-off speed will be reduced and} the turn-off ability will be weakened. If gfs is too large, it will cause the turn-off to be too fast and the EMI characteristics to be poor. At the same time, the drain-source will produce a larger turn-off voltage spike during the turn-off.

Ciss represents the input capacitance, Ciss ₌ Cgs ₊ Cgd _{. This parameter will affect the switching time of MOS. The larger the value, the slower the turn-on and turn-off time will be under the same driving capability, and} the greater the switching loss will be.

C _oss represents output capacitance, C _oss = C _ds + C _gd ; C _rss represents reverse transfer capacitance, C _rss = C _gd (Miller capacitance). These two parameters have a slight impact on the MOSFET turn-off time, among which C _gd will affect the amount of voltage energy transmitted to the MOSFET gate when the drain has an abnormally high voltage, which will have a certain impact on the lightning test items.

Q _g , Q _gs , Q _gd , t _d(on ), t _r , t _d(off) , t _f are all parameters that are interrelated with time. The faster the switching speed, the smaller the switching loss, the higher the efficiency, and the lower the temperature rise. The corresponding disadvantages are poor EMI characteristics and too high a MOSFET turn-off spike.

_{If the parameters IS} and I _SM are too small, there will be a risk of current breakdown.

If V _SD and t _rr are too large, it will cause excessive system loss and excessive temperature rise in bridge or LCC systems.

Q _rr This parameter is proportional to the charging time, and generally the smaller the better.

The output characteristic curve is a curve used to describe the relationship between the current and voltage of the MOS tube. The characteristic curve will be affected by the junction temperature. Generally, the data manual will list the characteristic curves at two temperatures.

According to the output characteristic curve of the MOS tube, take a point in U _ds and then use the method of graphing to obtain the corresponding transfer characteristic curve . From the transfer characteristic curve, we can see the relationship between I _d and U _{gs when U ds} is a certain value .

The on-resistance of MOS changes with the junction temperature with a positive temperature coefficient, that is, the higher the junction temperature, the greater the on-resistance. The MOS data sheet generally draws a curve of on-resistance changing with temperature when VGS=10V.

The smaller the capacitance value, the smaller the total gate charge Q _G , the faster the switching speed, and the smaller the switching loss. Applications such as switching power supplies and DC/DC converters require a smaller Q _G value.

MOS tubes generally have a parasitic diode, which protects the MOS tube. Its characteristics are the same as those of ordinary diodes, and it also has the characteristic of forward conduction.

The maximum safe operating area is a two-dimensional area formed by a series of (voltage, current) coordinate points. The voltage and current of the MOS tube when working cannot exceed this area. If they exceed this area, there will be danger.

It can be seen that there are actually many related parameters of MOS tubes. In fact, in general applications, we mainly consider parameters such as drain-source breakdown voltage V _DS , continuous drain current _ID , on-resistance R _DS(ON) , maximum dissipation power PD _, turn-on voltage V _GS(th) , switching time, operating temperature range, etc.

From | Electronic Circuits

annysky2012

Another very important factor is the selection of gate resistor.

ZGY13378662809

very nice