MRFX1K80NR5 rapidly increasing idle current problem.

cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

MRFX1K80NR5 rapidly increasing idle current problem.

Jump to solution
1,161 Views
na3m
Contributor I

Hello,

I am trying to replace MRF1K50H with MRFX1K80NR5 and having strange problem. I cannot set idle current at 1A level. I slowly increase bias voltage and when idle current is around 0.8A it starts growing by itself rapidly and can reach very high values. I turn off power to transistor to prevent it from damage.

Bias voltage is stable. What could be causing this? 

I know that MRFX1K80NR5 does not have flanges so I carefully attached transistor to copper plate with water cooling (using Liquid Ultra as thermal paste) to make sure it will have adequate cooling. Is there something else I am missing?

Thank you,

Nick NA3M

P.S. Transistors were bought from Mouser.com. I do not see NXP letters on them - just some strange logo.

Labels (1)
  • RF

0 Kudos
1 Solution
1,140 Views
LPP
NXP Employee
NXP Employee

Sure, the drain current increases because of tha device self heating.

The drain-source current of a power LDMOS device is strongly impacted by temperature. In Class AB and for a given VGS, the IDQ rises with temperature.

MRFX1K80H datasheet Figure 3 provides graphs of normalized VGS versus Quiescent Current and Case Temperature.

Also, below are the curves I obtained using the MRFX1K80H model for ADS.

LPP_0-1636104153252.png

 


Useful documents on the topic:
https://www.nxp.com/docs/en/application-note/AN1977.pdf
https://www.nxp.com/docs/en/application-note/AN1643.pdf

Best Regards
Pavel
NXP CAS

View solution in original post

1 Reply
1,141 Views
LPP
NXP Employee
NXP Employee

Sure, the drain current increases because of tha device self heating.

The drain-source current of a power LDMOS device is strongly impacted by temperature. In Class AB and for a given VGS, the IDQ rises with temperature.

MRFX1K80H datasheet Figure 3 provides graphs of normalized VGS versus Quiescent Current and Case Temperature.

Also, below are the curves I obtained using the MRFX1K80H model for ADS.

LPP_0-1636104153252.png

 


Useful documents on the topic:
https://www.nxp.com/docs/en/application-note/AN1977.pdf
https://www.nxp.com/docs/en/application-note/AN1643.pdf

Best Regards
Pavel
NXP CAS