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PTH12040WAZ not putting out more than 10A

Naji Naufel
Intellectual 805 points
Other Parts Discussed in Thread: PTH12010W, PTH12040W

I have a customer who is using the PTH12040WAZ in his board and during testing, some of the modules max out at about 10A when others go up to 40A.

 

What could be causing this?

Could it be mislabeled PTH12010W module?

  • 0
    TI__Mastermind 38230 points

    The PTH12040 has a  rated to a maximum  current of 50A with many thermal considerations based upon output current and  air flow across the module.( See the thermal; SOA data)

    A number of questions concerning the applcation.

    1. What is the input voltage , input power supply current  rating?How long are power leads  between 12040W , input power source and the module?

    a.What is the output voltage set to and maximum output current ?

    b. Is the electrical  testing completed in  a bench environment  in the final soldered  into copper assembly and layout?  details of the their layout and copper plane attachment? How many vias are used for inner layer attach for best thermal performance?

    b1.  Does the PTH12040 operate for a period of time before  output current and voltage are decreasing?

    c. What are the output capacitors , total capacitance, type,  value and ESR of each capacitor,

    c1.Output capacitor part number? 

    d. What is  the input capacitor , type rms ripple current rating and part number ? 

    2. Is the  UVLO circuit used in this  application attached to    pin8 UVLO?

    3. Is the output remote sense directly connected to the ouput bus?

    Can you send me a a schematic  of this application with all input and output capacitors? remote sense connection?

    Tom

  • 0 in reply to Tom Guerin
    Intellectual 805 points

    Hi Tom,

    The schematics is attached.

    Vin = 12V. Capacitor part numbers are listed on drawing. I asked this morning about the Sense pins but have not received an answer yet. I will also forward the other questiones you asked.4035.PTH12040WAZ_Schem.pdf

     

     

  • 0 in reply to Naji Naufel
    Intellectual 805 points

    Tom,

     

    While studying the schematics, I saw that the MC33161 driving the EN pin of the PTH has an open collector output and there is no external pull up resistor in the circuit.

    If the EN pin is floating, will that limit the current output or just chut down the output completely?

  • 0 in reply to Naji Naufel
    TI__Mastermind 38230 points

    The EN ( Inhibit pin is pulled up internally to 5V. There must be no pullup on this pin. The inhibit  control must be an open drain with no pullup internally from the MC33161 .

    Tom

  • 0 in reply to Tom Guerin
    Intellectual 805 points

    Tom,

    Were you able to get the schematics from this thread?

    Answers to Questions: (refer to schematic)

     

    1.  The input power supply is rated at 12VDC / 30.4A  (365W).

    The power supply is connected the module's PCB with twelve 16 AWG wires (6 Gnd, 6 Vsupply) each approx. 8 in. long.

     

    1a.  The PTH12040W output voltage is set to 5.02V (Rset = 200.0 ohms), Max. output current = 30A.

     

    1b.  The testing was completed on a lab bench with the final PCB assembly. 

    The PCB connects all in/out power and ground pins (1,2,3,4,5,6,9,10,12,13,15,16) of the module to their respective copper planes with a minimum of 7 via's each.

    No part of the module's top surface is uncomfortably hot to touch.

     

    2.  Typically a "bad" module will only fail when tested at output currents exceeding 10A, When tested at 16A, after several minutes the output voltage starts dropping out.

    The "drop-out" failure mode:  5V output falls to 0V for approx 20ms then soft-starts back to 5V. This repeats intermittently. Note: the output load is a resistor network connected thru 3 feet of 10 AWG wire.

     

    3.   Output Caps(2): C1,C2: Panasonic #EEU-FM1C102 - 1000uF / 16V. ESR=.019 ohms. Iripple=2.18A.

    3a.  Input Caps(2):  C3,C4: Panasonic #EEU-FM1V471 - 470uF / 35V. ESR=.019 ohms. Iripple=2.18A.

     

    4.  The UVLO threshhold is set to approx 10.5V with a 60.2k 1% resistor from pin 8 to ground.  However, I've removed this resistor allowing the UVLO pin to float on a bad module, same failure. 

     

    5.  The +Sense, -Sense pins are typically connected directly to the output bus. However, I've allowed these pins to float on a bad module, same failure.

     

     

  • 0 in reply to Naji Naufel
    TI__Mastermind 38230 points

    Naji:

    Can you send me an e-mail directly with your contact information? I would like to discuss this module  with you

    my e-mail is tguerin@ti.com

     

    Regards

    Tom