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XTR305: Hardwarepart for 0-10V / 0-20mA is getting very hot.

Markus Baisch
Prodigy 10 points
Part Number: XTR305
Other Parts Discussed in Thread: XTR300

Hello!

I have some questions about thermal problems on my pcb. 
I designed a PCB for 0-10V / 0-20mA Output. It's was driven by ESP32. With my software I can switch from 0-20mA to 0-10V output.
So I copy the reference design for my application. But it getting very hot (about 35-40 degrees).

I didn't find out why my board was getting hot. 

The power comes from an MEV1D2415SC. For the logic power I use a UA78M33 for 3.3V

I have tested some changes, but without any solution. By the way: The application is working very fine. The only thing is to reduce the temperature.

Best Regards
Markus

  • 0
    TI__Guru 55466 points

    Hi Markus,

    Is the XTR305 (U3) or one of the regulators causing the board to heat?  

    The XTR305 PowerPAD needs to be connected to a power plane capable of removing heat from the IC.  The thermal impedance specifications for the XTR300 are based on a PCB layout that properly removes heat from the XTR305 PowerPAD.  On the XTR305, depending on the load condition and current output of the XTR305, the device is expected to dissipate power.   As an example, while sourcing 20mA output current with small load resistance of 100-Ohm, the voltage at the XTR305 output is around 100-Ohms*20mA= +2V.  Therefore, the power dissipated by the XTR305, in this particular example would be as high as (+VS -  Vout)*Iout = (+15V – 2V)*20mA= ~260mW.

    Information on this topic is provided at the end of the XTR305 product datasheet.  I've copied some of the information below. 

     

    Similar layout guidelines should apply to the voltage regulators to dissipate heat.

    Thank you and Regards,

    Luis

  • 0 in reply to Luis Chioye
    TI__Guru 55466 points

    Hi Markus,

    There is a short tutorial that may be helpful on the TI- Precision Labs video series. This session addresses relationship between power and temperature in operational amplifiers.  The general concepts discussed apply to the XTR305.

    Please find below,

    https://training.ti.com/ti-precision-labs-op-amps-power-and-temperature

    Kind Regards,

    Luis

  • 0 in reply to Luis Chioye
    Prodigy 10 points

    Dear Luis,

    I check the design again and thank you for your hint. 

    In the first version of board, we make a mistake and connect the Power-Pad to GND. 
    So we change this from GND to V-.

    :-D 
    Now the V- power pad is an inner layer of our 4-Layer PCB. So now this clear. The heat cannot move away from the XTR305. I will do the new design work and I think that this will resolved my issue.

    Big thank to you!

    Best Regards
    Markus

  • 0 in reply to Markus Baisch
    TI__Guru 55466 points

    Hi Markus,

    Thank you, let us know if you have questions.

    Kind Regards,

    Luis