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TPS63031 Problem

jwizard jwizard
Prodigy 90 points
Other Parts Discussed in Thread: TPS63031, TPS63030

I am having problem with your TPS63031. For the start: schematic is exactly the same as in datasheet, PCB layout is also the same. Load current is 30mA.

Problem is: when input voltage is bigger then 2.9V everything is ok i see 3.3V on output. But when supply voltage is lower then 2.9 V output is unregulated(it is lower than supply voltage and rises with supply voltage).

I tried to change suply voltage from 1.8V to 4.5V. From 1.8V to 2.9V output is unregulated and supply current rises up to 0.4A. When i reach 2.9V supply current falls and converter starts to work normally.

What can be the reason of such behavior?

  • 0
    TI__Expert 8420 points
    What is your load type? what power source are you using to power your board?
    Could you exclude any soldering problems? Can you also test without load?
    Did/Could you try to conduct the same tests on the TPS63030EVM?
  • 0 in reply to Sabrina
    Prodigy 90 points
    Load type is active - 2 microwave amplifiers. But the same result is for pure resistive load from open to 100 Ohms. Soldering is ok. Effect takes place on all 24 boards. We dont have EVM and could not find tps63030 for tests. Power source was laboratory power supply and NI-MH baterries.
    Another issue was that device started to oscillate if started from 4.5V and higher supply. This problem was solved by adding 1nF and 0.1uF ceramic capacitors on input and output.
  • 0 in reply to jwizard jwizard
    TI__Expert 8420 points

    I understand that you followed the datasheet guidelines for the schematic and the layout, still I would like to take a look at it, could you please share it?

    You still see these oscillation when powering the board with a battery? 

    Could please post a scope plot with Vin and Vout when the circuit is unstable?

  • 0 in reply to Sabrina
    Prodigy 90 points

    Sorry  for disturbing Sabrina. I missed power ground under IC.