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TPS54200EVM-818: Troubleshooting the EVM

Patrick Hochleitner85
Prodigy 110 points
Part Number: TPS54200EVM-818
Other Parts Discussed in Thread: TPS54200, INA199

Hello all,

I've being using the TPS54200EVM to develop a battery charger for a health application. In order to test it, I tried using the Battery emulator mentioned in the following link. The charging profile is assured by a MSP430 that will generate the TPS54200`s PWM input signal, according to the Battery emulator's charge. 

The problem is when I assembled all of the system, the supply voltages dropped (in what seemed to be a great current increase). I checked the TPS54200 if I still had any current flowing out but I couldn't measure anything. The feedback voltage also gave me nothing.

I took the TPS54200EVM out of the circuitry and did some measuring a part. With a 12V Vin and a 3.3V 50KHz PWM signal I had absolutely nothing at the output. I tried using various power resistors (3.3 Ohm, 5Ohm, 13Ohm). I still had nothing on the output. I wonder if there is something wrong with the IC. Measuring direcly at the IC"s pads I verified that the integrated regulator is still delivering 6V as described in the datasheet for Vin> 6V. No signal is being delivered out the SW pad.

I ordered some TPS54200 samples so I can change it at the EVM if needed. But before doing such a thing, do you think there is any other test I can make to verify that the IC is actually fried?

I used a LRC meter and a voltmeter to verify that the passive components are still functioning , and it appears that C4 is no longer good. Could he be the reason the EVM is not functioning properly? 

I thank you in advance for the help.

Patrick

  • 0
    TI__Expert 4445 points

    Hi Patrick,

    If C4 is damaged, output cap, it will impact the EVM function.

    Any other question please let me know, thanks!

    Summer

  • 0 in reply to Summer SU
    TI__Prodigy 110 points

    Hello Summer,

    Thank you for your quick answer.

    I understand that the malfunctioning C4 will affect the EVM. But I would just expect that the signal would be less regulated instead of not having any signal at all.

    As I said before, I have no reference voltage on the FB pin and consequently (or inversely) no current on the output flowing to on my charge. Do you think the output cap is responsible for all these problems?

    Thank you again.

    Best regards,

    Patrick 

  • 0 in reply to Patrick Hochleitner85
    TI__Expert 4445 points
    Hi Patrick,
    I am sorry I can't say it must be the output cap damaged to caurse it.
    If the output cap damaged and there is some over stress in the output pin.
    It will damage the device.
    I hope this can answer your question.
    Thanks!
    Summer
  • 0 in reply to Summer SU
    TI__Prodigy 110 points
    Thank you again, Summer. I think I found the problem. The LED I was trying was dead and the other resistances were to high. I tried it with an 1ohm power resistor and it worked.

    This brings me to one last question, do you think that this TPS54200 could function having a battery as its load?

    Keeping in mind that its not being able to drive any current to loads with more than 2Ohms.

    It is maybe silly to ask it at this point seeing that this is the essence of the project, but better late than ever.

    Regards,

    Patrick
  • 0 in reply to Summer SU
    TI__Prodigy 110 points
    Moreover, I tried using an INA199 to monitor the current. I connected the Output of the INA199 to the FB input of the TPS54200 so that it will force the voltage reference at the Vout of the INA and as such imposing the current on the Rshunt (between IN+ and IN - from the INA 199). The value of Rshunt = Rsense from the TPS.

    The problem is that I'm not having any signal at the FB node. Do you know how can I assure a feedback voltage using such a design?

    If you want I can send you the circuit schematics so it will be more clear.

    Thank you in advance.

    Patrick Hochleitner
  • 0 in reply to Patrick Hochleitner85
    TI__Expert 4445 points

    Hi Patrick,

    Could you send me the file with question to summer-su@ti.com directly?

    Thanks!

    Summer