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PTR08100W is getting hot normal?

Christoph Boss
Prodigy 30 points
Other Parts Discussed in Thread: PTR08100W

Hello

 

Im using the PTR08100W to build the 5V for my firewall ( a small PC).

The firewall uses max 5A. Normaly it needs 2-3A.

Im using the circuit diagram from page 1 of the data sheet.

The input voltage is 12V.Here are some more data.

Ci=330µF

Co=330µF+2200µF+1000µF=3500µF

parallel to Ci and C0 are 2 ceramic Capacitors 10uF.

 

My question

Is it normal that the PTR08100W (special the inductor). Its getting so hot that I cannot touch it longer than 1 sec.

 

Greetings Christoph

  • 0
    TI__Mastermind 38230 points

    Christoph :

    The PTR08100 must be hard soldered into copper plane or multiple copper surface areas of 100mm x100mm . The thermal data indentifies with 12Vin and 5Vout the following thermals;

    1. At 2 Amp load, 5Vout and 12Vin  natural convection (on a Bench) the inductor temperature is 72°C when soldered into the copper area of 100mm x100mm or a 46°C rise above the 25°C . The maximum operating temperature is 83°C.

    2. At 5 Amp load, 5Vout and 12Vin  natural convection (on a Bench) the inductor temperature is 88°C when soldered into the copper area of 100mm x100mm or a 63°C rise above the 25°C . The maximum operating temperature at 5 Amps is 66°C.

    Tom

  • 0 in reply to Tom Guerin
    TI__Mastermind 38230 points

    One additional comment concerning the output capacitance limits. The absolute maximum polarized capacitance is limited to total 3000uF with a  parallel minimum ESR ( equivalent Series resistance ) of ≥7mΩ.

    Tom

  • 0 in reply to Tom Guerin
    Prodigy 30 points

    thank you for the answer.

     

    The problem is that the circuit board is only 4x3cm big. I didnt knew that I need a copper surface area. ;-)

    The problem is that the Ground pin is in the middle. So its imposible to make a Ground surface area.

    Do you think its better to remove one of the Capacitor. 

    Another question.

    Can the PTR08100 run without any load?

    Can the PTR08100 run without any copper surface area if i put a small fan there?

  • 0 in reply to Christoph Boss
    TI__Mastermind 38230 points

    Christoph ;

    Thanks for the addtional questions.

    1. Do you think its better to remove one of the Capacitor. 

    I would remove at least 500uF of capacitance . On a 5V bus, the   transient is on 150mV on a 50% to 100% load step. This is only changing the  5V by +/- 4.85V to 5.15V. It is therefore possible to decrease the output capacitance

    Another question.

    Can the PTR08100 run without any load? The PTR series can operate to no load, but the output ripple at no load with be variable.

    Can the PTR08100 run without any copper surface area if i put a small fan there?

     A fan with good airflow will decrease the average inductor temperature by about 10°C. Can you add  inner PCB copper layers to improve the thermal performance?

    Tom

  • 0 in reply to Tom Guerin
    Prodigy 30 points

    Hello

    No ca can´t add inner PCB layers. Im a Student and we only can produce double site boards.

    Will the PTR08100  shut down when he is getting to hot?? The next days i will remove one of the capacitor.

  • 0 in reply to Christoph Boss
    TI__Mastermind 38230 points

    Christoph:

     

    The PTR08100 does not have thermal  shutdown. The fan may be the only cooling method  available to prevent thermal overstress at high ambient temperatures.

    The other alternative to select another physically larger power module PTH08T230WAD with 6 Amp rating . There will be no thermal issues with this module. It size is 0.620" x 0.745". The input voltage range is 4.5V to14V.

    Tom

    The link to PTH08T230 is:

     

    http://focus.ti.com/docs/prod/folders/print/pth08t230w.html