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I'm currently using Texas Instruments TPS61025DRCR voltage regulator in a project (digikey link. When attempted to be powered with a 3V input, the regulator input voltage drops down to ~1.4V. When I unplug the 3V power source and measure its voltage, I again receive 3V. Thus, the issue has something to do with interfacing with the regulator.

My regulator circuit is illustrated below.

enter image description here

Note that this circuit was influenced by the TPS61025DRCR manual here.

Here is what I have done to troubleshoot the issue so far:

  • Because VIN_RAW (per my diagram) is dropping to 1.4V, I first checked to make sure that there was no short circuit from VIN_RAW to GND. I was able to verify that VIN_RAW is not short circuited anywhere.
  • I next verified that none of the solder on the pins had bridged.
  • I then verified that the VCC (voltage regulator output) was not short circuited (or had low resistance to ground).

I'm looking for a little feedback on other potential errors. Things I can think of:

  • I used too much hot air when soldering and just broke the chip.
  • There is something wrong with how I designed my circuit.

Any ideas?

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    \$\begingroup\$ If the input voltage is dropping, I'd suspect that your 3.3 volt source is not capable of providing the current required by the regulator. Details of the 3.3 volt source are required. \$\endgroup\$ – Peter Bennett Jan 13 '17 at 17:43
  • \$\begingroup\$ @PeterBennett VIN_RAW is capable of sourcing 150mA. However, if 150mA was actually being pulled, the resistance measurements I've taken from VIN_RAW to GND, and VCC to GND don't suggest that could happen. \$\endgroup\$ – Izzo Jan 13 '17 at 19:04
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After a little more debugging, I was able to find the issue with the circuit. The following were my debugging steps:

  • As Peter Bennett suggested, a source voltage that 'sags' (i.e. 3V -> 1.4V) when loaded suggests that the load has high current draw, such that the source can't source enough current. The measured current was found to be 400mA - way too high.
  • The next step was determining what was drawing so much current. Although I had measured and determined there were no short circuits, I did not account for active components that could become shorts under the right conditions. After analyzing the circuit, there had been a single TVS diode that had been damaged which would clamp when 3V was applied. Essentially, the short circuit only existed when adding power.

Key takeaway: if there appears to be a short in your circuit but you measure none, always keep in mind that an active component (such as a TVS diode) could be the culprit.

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