LM2936: Lm2936 heat problem

Ihab Alsheikh

Intellectual 255 points

Part Number: LM2936

Hi TI Expert

I have an over heat problem in LM2936MP-5.0 When the external power is 30 V.

The load current is below 30 mA.

Regards

Ihab

over 4 years ago

0 Jason Song over 4 years ago

TI__Mastermind 23361 points

Hi Ihab,

What's the output voltage of the LDO and in what package? When you say heat problem, did the regulator hit thermal shutdown?

Regards,
Jason Song

0 Ihab Alsheikh over 4 years ago in reply to Jason Song

Intellectual 255 points

Hi Jason
The output is 5V in package LM2936MP-5.0_NOPB ( SOT-223).
the heat problem by hand touching , It is too hot that you can't touch it,
We should consider that there is a packaging stage and it will be hotter

Regards,

Ihab Alsheikh

+1 Jason Song over 4 years ago in reply to Ihab Alsheikh

TI__Mastermind 23361 points

Hi Ihab,

The LDO has a recommended junction temperature of up to 125C. I would not recommend using your finger to sense the temperature. Instead, please use a thermal gun or estimate the temperature by using (Vin-Vout)xLoadx Rja, the Rja for SOT-223 is 59.6C/W.

Regards,
Jason Song

0 Ihab Alsheikh over 4 years ago in reply to Jason Song

Intellectual 255 points

Hi Jason,

Thank you for your replay.

Jason Song said:
(Vin-Vout)xLoadx Rj

(Vin = 30 V, Vout = 5V , Load = 30 mA)

that means the estimated temperature of LM2936 is 44.7.
adding the ambient temperature (40 C) which means 84.7 C. am I right?

The board which I used will work all the day, Could I face a problem because of regulator heat ?

Regards,
Ihab

+1 Jason Song over 4 years ago in reply to Ihab Alsheikh

TI__Mastermind 23361 points

Hi Ihab,

Yes, your calculation is correct. The LDO is designed to operate under 125C and you are good.

Regards,
Jason Song

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LM2936: Lm2936 heat problem