some questions about the datasheet of MRFE6VP61K25HR5

[阳城里恩]

Hello all,

I'm using MRFE6VP61K25HR5. But I come across some problems because I just set foot in this area.

1、If the thermal resistance Rθjc=0.15℃/W obtained in this way:（225℃-25℃）/1333 W=0.15℃/W?If so,it shows that the RF Power LDMOS Transistors have a good heat sink so that its junction temperature is maintained at 25℃ ?And then what's the thermal resistance between junction and environment without heat sink?The datasheet does not seem to be given.

2、How the data 6.67W/℃ obtained in the datasheet?

3、In the table 2,what does "Zθjc=0.03℃/W" mean?And how it obtained?

4、Why the datasheet have not support the thermal impedance curve of RF Power LDMOS Transistors?

5、What is the difference between MRFE6VP61K25HR5 and MRFE6VP61K25HR6?

hope some help.

thanks in advance,

Best Regard,

Lee.

[LPP · Accepted solution]

1.
Thermal measurements methodology is described in this document:
https://www.nxp.com/docs/en/application-note/AN1955.pdf

The temperatures during measurements was not 225'C and 25'C. Datasheet provides actual case temperature during measurement (63' or 66'C).
Die and case temperatures was measured by IR sensor and thermocouple. Power dissipation was measured by the DC power supply. The Rθjc value has been calculated from the measured values.

MRFE6VP61K25HR5 is a very high power device. It can't be used without heat sink. Thus, junction-to-environment resistance is not a useful parameter for this transistor and it is not measured and not provided in the datasheet.

2.
Power derating factor is a reverse value for Rθjc.   1/0.15['C/W] = 6.67[W/'C]

3.
The same measurements was performed as for Rθjc. However, the pulsed input signal was used. Average DC power was used to calculate thermal impedance.

4.
We have no specific reasons. Typically, RF transistors are designed for specific applications (continuous or pulsed). If a transistor is designed for wide range of pulse widths than we specify thermal impedances for different widths or provide a graph.

For example, see Figure 12:
https://www.nxp.com/docs/en/data-sheet/MMRF1006H.pdf

By the way, the thermal impedance graphs for MRFE6VP61K25HR5 are expected to be the same.

5.
These are the same transistors but supplied in different rail packages.
Have a great day,
Pavel
NXP TIC

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[阳城里恩]

Thank you very much!!!