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LM2937: IMP to IMP/NOPB

user6498224
Prodigy 10 points
Part Number: LM2937

Hello, 

We are having problems with the LM2937IMP-3.3. 

Have used the part in our design for the last 6-7 years without issue. 

Now however. it appears on new systems, the LM2937IMP-3.3 is overheating after running for a short period, the thermal shutdown protections trips, shutting down the output.

We are looking for possible reasons for this.

Have noticed that the part number has changed, LM2937IMP-3.3 is now LM2937IMP-3.3/NOPB.

NOPB = Lead free. 

When exactly did this change take place?

Has the thermal performance of the chip been in anyway compromised by changing to Lead free?

The materials used internally must have changed.

Best regards,

Conor

  • 0
    TI__Mastermind 43505 points

    Hi Conor,

    It looks like the NOPB versions were added to the datasheets in 2013. 

    The thermals might change a little bit with the lead-free versions, but we do not expect the change to be very significant. 

    I have some questions regarding the use of LM2937 in your systems.

    1) Is the PCB layout different for the new systems? If there is a smaller copper heatsink near the LM2937 it could enter thermal shutdown sooner with the same loading conditions. 

    2) Is it happening to multiple units or is it isolated? If it is an isolated event have you done an A-B-A swap to see if the failure follows the part or is the result of insufficient solder coverage?

    3) Do you have any of the PB parts left that you could populate on the failing board to see if it reverts to its previous performance?

    Best regards,

    Nick