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TPS63002 Heating Up

Aditya Ayachit
Prodigy 80 points
Other Parts Discussed in Thread: TPS63002, TPS63000EVM-148

5822.JO-11-11-V1.pdf

Hi!

Please find the attached PDF for the implemented TPS63002 design.

The EN_USB signal is coming from the uc (An MSP430)

When the IC is disabled, it is not heating up. But when enabled it heats up, even though no load is connected to it.

When checked on oscilloscope the 5 V Waveform is seen, though it is still a little choppy.

Initially the powerpad was not connected to ground, but it is now connected to ground.

The source of power is Li-Ion battery. Is it necessary to PS/SYNC to ground if using a Li-Ion battery?

Could this be because of the selection of inductor and capacitor?

Looking forward for assistance.

Kind Regards,

Aditya Ayachit 

  • 0
    TI__Mastermind 30280 points

    Aditya,

    First of all, let me make sure we are on the same page. Is the PowerPAD connected to PGND or GND? Please confirm that it is connected directly to PGND (Power ground) and not just GND (Control/logic ground) before we move on.

    After this is confirmed, a quick calculation would show that the power dissipated from quiescent current alone would be approximately 50uA*5.5V = 0.275mW, and the maximum power dissipation of the package is 820mW. It seems that if the PowerPAD is well soldered to PGND that there should be sufficient power dissipation capabilities.

    As a follow-up, how hot is the part getting? Are you measuring the temperature?

    Also, as a side note, since the part is designed for use with single cell Li-Ion batteries, it would not be sufficient to say that it is necessary to ground PS/SYNC if using a Li-Ion battery. Rather, it may be necessary to ground PS/SYNC if you intend to use the part with a light load or no load and efficiency is crucial.

    Finally, although this is not exactly a direct solution, is there any way for the MSP430 to know that the load is connected? If you know when the load is not connected, maybe you could just shut down the TPS63002 and indirectly solve the problem you are experiencing.

    Hopefully we will resolve this problem soon for you.

     

    Regards,

    Brian

  • 0 in reply to Brian Berner
    TI__Mastermind 30280 points

    Aditya,

    I have a couple follow-up notes that may or may not be related to the problem but will definitely affect circuit operation in positive ways:

    The input capacitor, Cin, does not appear in the schematic you attached in the original post. It is recommended that this capacitor be at least 4.7uF

    The output inductor, L, according to equation 4, could probably be reduced t o3.3uH if board space is a concern, as the value I calculated was 3.07uH using 1250kHz and the minimum input voltage, 1.8V

    Given that you are using 4.7uH, equation 7 suggests the output capacitor, Cout, be at least 5*L, and therefore the output capacitor should be at least 23.5uF for 4.7uH and at least 16.5uF should you use a 3.3uH inductor.

    Please consider these suggestions and other design considerations in the TPS63000EVM-148 as other possible solutions to the problem and reply if you have further questions/concerns.

     

    Regards,

    Brian

  • 0 in reply to Brian Berner
    Prodigy 80 points

    Dear Brian,

    Extremely sorry for the large delay in response.

    Please find my answer below:

    First of all, let me make sure we are on the same page. Is the PowerPAD connected to PGND or GND? Please confirm that it is connected directly to PGND (Power ground) and not just GND (Control/logic ground) before we move on.

     Initially the PowerPAD was not connected to PGND or GND. We have taken the necessary action.

      After this is confirmed, a quick calculation would show that the power dissipated from quiescent current alone would be approximately 50uA*5.5V = 0.275mW, and the maximum power dissipation of the package is 820mW. It seems that if the PowerPAD is well soldered to PGND that there should be sufficient power dissipation capabilities.

     I agree. I have used this part before and never had this problem.

    As a follow-up, how hot is the part getting? Are you measuring the temperature?

    Though we have not measured the temperature, the part is getting very very hot. It is even heating up the surrounding PCB. Also we have changed the IC and the problem persisted in the new IC also.  

    Also, as a side note, since the part is designed for use with single cell Li-Ion batteries, it would not be sufficient to say that it is necessary to ground PS/SYNC if using a Li-Ion battery. Rather, it may be necessary to ground PS/SYNC if you intend to use the part with a light load or no load and efficiency is crucial.  

    We have currently permanently connected the PS/SYNC to the supply of the Li-Ion battery. We intend that we will first get the IC working and then to improve the efficiency we would ground the PS/SYNC pin in the next iteration of the PCB. If you disagree please let me know. It's just that the IC package is so small and tracks are so close that I do not want to go for track cutting and stuff at this stage.

    Finally, although this is not exactly a direct solution, is there any way for the MSP430 to know that the load is connected? If you know when the load is not connected, maybe you could just shut down the TPS63002 and indirectly solve the problem you are experiencing. 

    I completely agree with you. But it is kind of Egg first or Hen first issue. I have to switch ON the supply, check if any device is connected to the USB (either by monitoring the current or the status of DATA+/- pins) and then keep the power ON. This I will have to do continuously. So it is a kind of polling. Or I would have to ask the user to press a button to inform the system that he has connected a device to USB, but it also has its own set of problems.

    We are currently working on the information which you have sent to us. We are sure that the solution suggested by you should work. We will respond as soon as we have done things as per your suggestions.

    Kind Regards,

    Aditya Ayachit

     

     

  • 0 in reply to Aditya Ayachit
    Prodigy 80 points

    Dear Brian,

    I believe that the issue is resolved. Though we have not undertaken load tests yet, but 5V now appears at the output of the TPS63002, without any heating.

    The problem, we believe, resided in the selection of the inductors. We had used SMD 1206 inductors of which no datasheet was available to us. Changing the inductors with the ones which we use in our standard product resulted in resolution of the issue.

    There is no heating, in spite of the fact that PS/SYNC is tied high. Your suggestions about the same will be tested and later implemented in the final design.

    Thanks for the support. I will update again once we have taken the load trials.

    Kind Regards,

    Aditya Ayachit 

     

  • 0 in reply to Aditya Ayachit
    Prodigy 80 points

    Dear Brian,

    The input capacitor is actually present in our circuit, but not shown in the schematic presented to you. The value of the capacitor is 10uF.

    We are in the process of testing the circuit on load and are facing certain problems. But we will notify about the same once we are sure that we have implemented your suggestions.

    Thanks a lot for your prompt support. I am sure this thing will resolve by tomorrow.

    Kind Regards,

    Aditya Ayachit