MOSFET with Same Part.No and Different Datasheet

[akh_power]

I am using the Cree C2M0025120D device for my research purpose. I have found recently that the datasheet of the device now shows different specifications compared to the previous datasheet of the same device. The link for both the datasheets are given below :

Old : https://www.farnell.com/datasheets/2048144.pdf
New : https://assets.wolfspeed.com/uploads/2020/12/C2M0025120D.pdf

Is it common to have device with same part number to gave different characteristics? Many important parameters of the MOSFET such as continuous drain current, Coss, Ciss, Diode forward voltage drop, Reverse recovery charge, Turn on time, Turn off time etc have changed.
I got into trouble when I had to change one of the MOSFET of a full bridge circuit which was using old C2M0025120D mosfets. Because, I had to change it with a new C2M0025120D mosfet and I was not aware of the change in the MOSFET characteristics. The turn-on time was drastically different (more than 500ns) for the 27 Ohm external gate resistance that I chose.
I believe manufacturers should not release products like this.

 

[KlausST]

Hi,

Is it common to have device with same part number to gave different characteristics?

At least it is not "uncommon".
That´s why there are different revisions of a datasheet (Without change in specification there is no need to have a different version)

Since there is a revision history missing one can only guess about the "why".
* modified production process
* unequal heat contribution over chip

In either case I recommend to follow the latest datasheet specifications.

Always use the datasheet directly from the manufacturer, because it will be most up to date. Usually the manufacturer internet site provides more informations (design tools, simulation tools, application notes, design notes...)

Klaus

 

[FvM]

"The information in this document is subject to change without notice"

Most likely Cree has ported second generation C2 devices to new C3 production technology. I see that the parameter changes might be critical for some application. Mixing "old" and "new" devices in a circuit is probably not recommended.

--- Updated Mar 15, 2022 ---

The turn-on time was drastically different (more than 500ns) for the 27 Ohm external gate resistance that I chose.

27 ohm is a way off standard values expected in the datasheet and applications circuits. You have apparently slowed down switching speed beyond usual SiC range, seeing Crss reduced from 15 to 9 pF has surely a drastical effect in this case. I can just guess that the change is smaller with standard Rg values.

 

[akh_power]

"The information in this document is subject to change without notice"

Most likely Cree has ported second generation C2 devices to new C3 production technology. I see that the parameter changes might be critical for some application. Mixing "old" and "new" devices in a circuit is probably not recommended.

--- Updated Mar 15, 2022 ---

27 ohm is a way off standard values expected in the datasheet and applications circuits. You have apparently slowed down switching speed beyond usual SiC range, seeing Crss reduced from 15 to 9 pF has surely a drastical effect in this case. I can just guess that the change is smaller with standard Rg values.

Regarding the turn-on gate resistance, I have tried lower values of gate resistances. With 20 ohm gate resistance (the maximum gate resistance they show in the characteristics plots) itself, the ringing in the gate voltage is too much. I am not confident to go to higher voltages, as I doubt the ringing can false trigger the MOSFETs and short the legs.

--- Updated Mar 15, 2022 ---

Hi,

At least it is not "uncommon".
That´s why there are different revisions of a datasheet (Without change in specification there is no need to have a different version)

Since there is a revision history missing one can only guess about the "why".
* modified production process
* unequal heat contribution over chip

In either case I recommend to follow the latest datasheet specifications.

Always use the datasheet directly from the manufacturer, because it will be most up to date. Usually the manufacturer internet site provides more informations (design tools, simulation tools, application notes, design notes...)

Klaus

Thank you for the advice. Looking for the latest version of the datasheet is a good practice to avoid these kind of troubles.

 

[FvM]

Regarding the turn-on gate resistance, I have tried lower values of gate resistances. With 20 ohm gate resistance (the maximum gate resistance they show in the characteristics plots) itself, the ringing in the gate voltage is too much. I am not confident to go to higher voltages, as I doubt the ringing can false trigger the MOSFETs and short the legs.

Suggests that wiring inductance of your layout is larger than usual. Gate voltage beyond maximum ratings should be avoided, it's at risk to damage the gate oxide.

 

[akh_power]

Suggests that wiring inductance of your layout is larger than usual. Gate voltage beyond maximum ratings should be avoided, it's at risk to damage the gate oxide.

I am not exceeding the gate to source voltage limits. With the ringing in the gate to source voltage, I am not confident to go to higher drain to source voltage(sorry, I forgot to mention drain to source voltage in the previous reply). So, I am using a higher gate resistance to reduce the ringing in the gate to source voltage.

 

[cupoftea]

you say you have ringing in VGS....are you sure you arent looking at the common mode noise in the scope trace?
Because you shoudlnt be seeing that ringing...unless you gate drive is very badly layed out.

Also, the newer device looks better....lower cds, ...trr is higher , but its measured at a much higher A/sec, so probably is actually better.
CISS has gone up about 10%...but that wont matter much in switching losses...because most of the time that ciss is getting charged up to vgs(th), the fet has not started porting current anyway.

But yes, sic is a new material, and there'll be changes to parameters as years go by.....but in your case, the new fet looks better to me, in pretty well every way.

If i'm honest though, i do think that Cree should have an "changes" page, to highlight these changes.

I googled "cree product change notification" and got nothing...so i do sympathise a little with your case.

 

[akh_power]

you say you have ringing in VGS....are you sure you arent looking at the common mode noise in the scope trace?
Because you shoudlnt be seeing that ringing...unless you gate drive is very badly layed out.

Also, the newer device looks better....lower cds, ...trr is higher , but its measured at a much higher A/sec, so probably is actually better.
CISS has gone up about 10%...but that wont matter much in switching losses...because most of the time that ciss is getting charged up to vgs(th), the fet has not started porting current anyway.

But yes, sic is a new material, and there'll be changes to parameters as years go by.....but in your case, the new fet looks better to me, in pretty well every way.

If i'm honest though, i do think that Cree should have an "changes" page, to highlight these changes.

I googled "cree product change notification" and got nothing...so i do sympathise a little with your case.

Some drawbacks of the new device are : Diode forward voltage drop increased, Reverse recovery charge increased, Continuous drain current rating almost decreased by 30%

 

[cupoftea]

Thanks, thats interesting about rev rec charge....i wonder if its because of the higher di/dt though?....others here will know if this is the cause of the higher Qrr?
I suspect that if tested at the same conditions, then trr and Qrr would be better for the newer device.......if not, then this is bad news, as low trr and Qrr is supposed to be one of the beautys of sic.

The Idrain....to be honest, its probably the same but they just got a bit more conservative in the datasheet......but yes, its a little disconcerting

Take your point about Vf.......

I guess they would make the excuse that sic is a new technology, and things are changing......you have raised a good point...beware SiC datasheet changes.

Having said that, sic vf has always been bad, and people are likely to add a pllel extra sic diode.........

But all said and done.........your point is a good one......this is the first case of " blurry datasheet " that i have ever experienced.