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PTH08T231W : Module destroyed while using continuous current.

Lewis Kevin
Intellectual 500 points
Other Parts Discussed in Thread: PTH08T231W
Thank you for your quick reply.
This is inquiries about another problem.

Test condition is like below :

input : DC12V Linear DC Power Supply used.
Output : 5V/5A Continuous current tested
Cooling : Air natural cooling
Around Temperature : 10 degrees Celcius

Problem :
After againg time 8hours, module is destroyed.

Question
As I mentioned above, tested temperature condition is 10degree, but actual
circumstances in reality will be 30degree celcius. By air natural cooling,
I'd like to know how long we can us continuous current.
  • 0
    TI__Mastermind 38230 points

    Bae Su-min :

    Thanks for the e-mail on the thermal  performance of the PTH08T231W with 12Vin and 5Vout at 5Amps.

    I have several questions and comments.

    1. What is the  complete part number used in this application is it PTH08T231WAS/WAZ (SMT) or PTH08T231WAD(T/H) .

    1A.If the  module tested was tested on a completely assembly PCB per the schematic sent in earlier,  what  solder   process  used? Is it lead  free or tin lead process?

    2. The tested   10°C ambient temperature no air  flow implies this assembly was located in an lower temperature oven? Is this true?

    2A. The normal room temperature is about 23°C to 27°C .

    2B Was this assembly tested and  located in a closed box  no air flow? The average ambient temperature in a closed box  environment can be as high as 60°C with  no air flow and or  natural convection air flow.

    2C. The thermal data on this module at 12Vin and 5Vout and 6 amps is rated to maximum to 85° ambient temperature when assembled in a enclosed case . The PTH08T231Wxx ambient temperature is measured 0.2cm from the inductor.

    Request the inductor temperature(thermal couple)  as measurement in the closed case environment.

    The published SOA thermal data requires the following

    SOA  curves represent the conditions at which  internal components  are at or below  the 
    manufacturer's  maximum operating  temperatures. Derating limits  apply  to the 
    modules soldered into  a 4" x4" double-sided PWB with 1 oz. copper. 

    Regards

    Tom

  • 0 in reply to Tom Guerin
    Intellectual 500 points 
    1. We are testing PTH08T231WAD.

    We do not know what tin lead process is, but we are not using Pb Free. We are soldering general copper by hand.

    B It is tested in opened LAB. Also, it will be used where is no air flow. We will use air natural cooling without fan.

    Temperaturen of inductor is more than 95degrees celcius in condition of 12V Input, 5V/5A Output and opened around temp 20degrees LAB.

    Let me ask you again.
    1. Could you guarantee us the maximum time when we use continuous current with 5V/5A Output and 12V input around 40 degrees celcius.

    2. We'd like to know the distance using V-Sensing. We will use about 2M long.

    Thank you.
  • 0 in reply to Lewis Kevin
    TI__Mastermind 38230 points

     

    Bae Su-min :

    Thanks for the data.

    I reviewed the questions concerning the PTH08T231WAD at 5Vout 5 amp load with 12Vin.

    1. (+)Remote sense

     Remote sense (R/S (+)pin 5  must be connected  directly  to the output bus(pin 4) plane  on the same PCB assembly. The (+) R/ S should not be connected through a pin/plug assembly to the (5V) Vout bus plane in another location.  A  2 meter (+) remote sense is not recommended for reliable operation. The load must be located on the same PCB as the power module to prevent unstable and erratic operation.

    a. I recommend the (+) R/S be connected directly to the output bus plane prior to the power exiting the power board for the following reason.

    a1.. Remote sense (+)   When the (+) remote sense is connected through a pin plug  and terminated at Vout bus beyond  the plug terminal, this can at times cause the  power module to fail.  If the Vout bus  through the plug connector is open  or intermittent, while the remote sense  and VOut bus is also connected this intermittent connection will overstress the module.

     This instability can occur  when the (+)  is connected and the  cause the erratic operation  of the  power module .

    a2 (+)Remote sense  from Product t specification PTH08T23x (Note) exceptions for (+)  remote sense connection toits  Vout power plane.

    The remote sense feature is not designed to compensate for the forward drop of nonlinear or frequency dependent components that may be placed in series with the converter output. Examples include OR-ing diodes, filter inductors, ferrite beads, and fuses. When these components are enclosed by the remote sense connection they are effectively placed inside the regulation control loop, which can adversely affect the stability of the regulator.

    2. (-) negative remote sense must be  connected to GND (pin 3), very close to the module (within 10cm) on its   primary PCB .

    3 .Power Module  Inductor temperature

    a. Mearured  Inductor  temperature of 95°C  in open air with 12Vin and 5Vout at 5Amps. The ambient temperature  (within 1cm) around the module is about  25°C.

    a1. The normal temperature on the inductor soldered into a copper plane based upon the SOA( Safe operating thermal data ) is about 90-95°C no air flow.

    a1 (cont) temperature Data from the product  specification when soldered under the  following conditions .

     "The temperature derating curves represent the conditions at which internal components are at or below the manufacturer's maximum operating temperatures. Derating limits apply to modules soldered directly to a 100 mm x 100 mm double-sided PCB with 2 oz. copper.

    a2. When the inductor temperature is 95°C at  operating voltage (12Vin, 5Vout at 5Amps  and soldered into a copper plane. The maximum recommended operating air temperture as measured within 1cm of the module inductor is limited to 60°C  with  nartural convection no air  flow enclosed case environment.

     Tom