We often use MOS with different packages, so I would like to ask what is the difference between MOS with DPAK and D2PAK packages?

小太阳yy

We often use MOS with different packages, so I would like to ask what is the difference between MOS with DPAK and D2PAK packages? [Copy link]

 

 

The following is some information I found, but in actual MOS applications, I found that the thermal resistance values of these two packages are the same. So, apart from the difference in size, what other differences are there between them?

I checked two datasheets and found that the smaller the size, the higher the current and withstand voltage. Why is that? Theoretically, the larger the size, the better the heat dissipation and the lower the thermal resistance, right?

chunyang

The packaging form does not determine the current carrying and withstand voltage parameters, which are determined by the tube core. The package is related to the power dissipation, which determines the so-called "thermal resistance". Generally speaking, this is the biggest difference between packages, but some different packages have the same power dissipation/thermal resistance. The reason why such packages exist is that they have evolved from different predecessors. Therefore, to compare, it must be based on the ratio of the same model from the same manufacturer, which means that the same tube core has different packages, so such a comparison is meaningful. However, the same model of products from different manufacturers may have different parameters due to different tube cores, and strictly speaking, they should be identified with different models. In the past, the model itself was exclusive, but later due to changes in the law, the exclusivity of the digital model no longer holds, which opened the door for many manufacturers to "ride on the popularity", so there is the so-called phenomenon that the same model has different basic parameters.

maychang

If they are products from the same manufacturer, then the same model but different packages (must have different suffixes) have the same electrical parameters, only the heat dissipation capacity is different. This must be noted in the datasheet.

maychang

"I checked two datasheets and found that the smaller the size, the higher the current and withstand voltage. Why is that? "

Small size does not necessarily mean small current and voltage parameters. Current and voltage parameters are determined by the die (including production process). The same package can have different dies or production processes.

小太阳yy

chunyang posted on 2022-3-1 16:48 The packaging form does not determine the current carrying and voltage resistance parameters, which are determined by the die. The packaging is related to the power dissipation, which determines the so-called "thermal resistance" ...

When MOS is working in the amplification region, doesn't thermal resistance mean the power that the MOS can carry? Why do MOS with very different nominal dissipated power have similar thermal resistance values?

小太阳yy

maychang posted on 2022-3-1 18:50 If it is a product from the same manufacturer, then the electrical parameters of the same model with different packages (must have different suffixes) are the same, and only the heat dissipation capacity is different. This is in the data ...

The greater the current carrying capacity of MOS, the greater the power dissipation, right?

maychang

Xiao Taiyangyy Published on 2022-3-1 20:59 Doesn’t the greater the current carrying capacity of MOS mean greater power dissipation?

"The greater the current carrying capacity of a MOS, the greater the power dissipation, right?"

That's not necessarily the case.

If you look at more models of power MOS, you will find that: with the same package, MOS tubes with low voltage resistance often allow larger current, and MOS tubes with high voltage resistance often allow smaller current, and the heat dissipation capacity of the two tubes is roughly the same.

小太阳yy

maychang posted on 2022-3-1 21:15 "The greater the current carrying capacity of MOS, the greater the power dissipation, right?" That's not necessarily the case. If you look at various models of power MOS, you will find...

In the circuit above, the MOS tube works in the amplification area. The power it carries is the input voltage minus the RS voltage and the load voltage, multiplied by the current passing through the MOS, and then the power of the tube is calculated by the thermal resistance. Why is the power obtained at this time so much smaller than the nominal dissipation power of the tube? If the power is too large, TJ will exceed 175. In this case, what is the use of the nominal power Ptot? Because the level of TJ depends entirely on the thermal resistance, what does it have to do with the maximum dissipation power? Moreover, I found that the thermal resistance of the MOS with a nominal dissipation power of 110W is smaller than that of the MOS with a nominal dissipation power of 4.7W to the PCB board than that of the MOS with a nominal dissipation power of 4.7W. So what is the use of this nominal power? In this case, I can directly calculate the maximum temperature rise by looking at the thermal resistance. What does it have to do with the dissipation power? What does it have to do with ID? The current calculated according to the PCB thermal resistance is very, very small. If it is slightly larger, the temperature rise will be very high, causing TJ to exceed 175

chunyang

小太阳yy posted on 2022-3-1 20:58 When MOS works in the amplification area, doesn't thermal resistance mean the power that the MOS can carry? Why is there a big difference in the nominal dissipated power of MOS, and the thermal...

Thermal resistance cannot be directly equated to the power that can be carried. Thermal resistance is related to the package, and the maximum value of the dissipated power is determined by the die and the package.

chunyang

Xiao Taiyangyy Published on 2022-3-1 20:59 Doesn’t the greater the current carrying capacity of MOS mean greater power dissipation?

That may not be the case. Note that the variables in the power calculation formula are not just current parameters.

chunyang

Xiaoyangyy posted on 2022-3-1 21:27 maychang posted on 2022-3-1 21:15 "The greater the current carrying capacity of MOS, the greater the power dissipation, right?" That's not necessarily the case. If you look more...

You still haven't figured out the relationship between thermal resistance and power dissipation. Let's put it this way, the two are unrelated. Low thermal resistance does not necessarily mean high power dissipation, and vice versa. It's just that usually tubes with high power dissipation tend to use low thermal resistance packages, but this is not necessarily the case.

chunyang

Each package has its own specific thermal resistance and corresponding maximum power dissipation, but there can be many types of dies installed in the package. For example, if a small-power die is installed in a large package, the maximum power dissipation is determined by the die instead of the package. Similarly, if a high-power die is installed in a small package, the high-power die cannot be fully utilized due to the limitation of the package, and the power dissipation limit is limited by the package. After understanding this, you should know that the relationship between heat dissipation conditions and maximum power dissipation is similar to the above. The key lies in understanding the nature of each parameter.

chunyang

You may wish to consider such a situation:

Suppose the same die uses two packages with different thermal resistances, but in application, the one with low thermal resistance does not use a heat sink, while the one with high thermal resistance uses a large heat sink to dissipate all the heat. Other conditions are the same, so which one has a greater actual power dissipation limit?

chunyang

Pay attention to the differences and connections between several concepts: the maximum dissipation power parameter of the tube, the maximum dissipation power parameter of the package, and the package thermal resistance.

maychang

Xiaoyangyy posted on 2022-3-1 21:27 maychang posted on 2022-3-1 21:15 "The greater the current carrying capacity of MOS, the greater the power dissipation, right?" That's not necessarily the case. If you look more...

"The power it carries is the input voltage minus the RS voltage and the load voltage, multiplied by the current passing through the MOS, and then the power of the tube is calculated by the thermal resistance."

How could this be possible?

In your sentence, the first half says that the power dissipated by the tube is the voltage across the tube multiplied by the current through the MOS , and the second half says that the power of the tube is calculated by the thermal resistance . This is self-contradictory.

The first half of the sentence is correct, and the second half is a fallacy.

maychang

Xiaoyangyy posted on 2022-3-1 21:27 maychang posted on 2022-3-1 21:15 "The greater the current carrying capacity of MOS, the greater the power dissipation, right?" That's not necessarily the case. If you look more...

"Because the level of TJ is completely determined by thermal resistance."

The junction temperature Tj is not [entirely determined by thermal resistance], but is also related to the power dissipated by the tube and the ambient temperature.

Imagine an extreme case: there is no current in the tube, and of course no power dissipation. At this time, the junction temperature must be equal to the ambient temperature and has nothing to do with thermal resistance.

小太阳yy

maychang posted on 2022-3-2 20:21 "The power it carries is the input voltage minus the RS voltage and the load voltage, multiplied by the current passing through the MOS, and then calculated by the thermal resistance of the tube...

The second half of the sentence is indeed wrong. The temperature rise is calculated by thermal resistance. It is a slip of the tongue.

小太阳yy

maychang posted on 2022-3-2 20:26 "Because the height of TJ depends entirely on thermal resistance." The junction temperature Tj is not [completely dependent on thermal resistance], the junction temperature is also related to the power dissipated by the tube and...

What I mean is that the maximum TJ of most MOS is 175 degrees Celsius. I understand that it is related to the ambient temperature. What I want to express is that, for example, two MOS with very different maximum dissipation powers have the same maximum TJ of 175 degrees Celsius, and their thermal resistance relative to the ambient temperature is also similar. Of course, under ideal heat dissipation conditions, such as TC is always at 25 degrees Celsius, then their dissipated powers must be different. When there is no heat sink, because their thermal resistance is similar and they are all attached to the PCB, their temperature rise is almost the same. Then what is the meaning of this so-called maximum dissipation power under the nominal ideal state?

小太阳yy

chunyang posted on 2022-3-2 17:38 Each package has its own specific thermal resistance and corresponding maximum power dissipation, but there can be many types of dies installed in the package. For example, installing a small...

Yes, that's my question. The high-power die is limited by the package to dissipate power. What's the point of making a high-power die? For example, a 100W die is placed in the same package as a 10W die. Their thermal resistance relative to ambient temperature is the same, and the highest TJ is 175. If I don't add a heat sink, what is the difference between these two MOS? There is no difference, and all the MOS we use do not have a heat sink. Do you have any examples of using a heat sink to share?

maychang

小太阳yy posted on 2022-3-2 21:13 What I mean is that most MOS have a maximum TJ of 175 degrees Celsius. I understand that it is related to the ambient temperature. What I want to express is, for example, the two maximum dissipated powers...

"For example, two MOS with very different maximum power dissipation have the same maximum TJ of 175 degrees Celsius, and their thermal resistance relative to the ambient temperature is also similar. Of course, under ideal heat dissipation conditions, such as TC is always 25 degrees Celsius, then they must have different power dissipation ."

I'm afraid that's where your problem lies. "Maximum power dissipation" and "power dissipation" are not the same thing. "Maximum power dissipation" is determined by the tube structure (including the thermal resistance from the tube core to the shell), while "power dissipation" is the actual power consumed by the tube.