LDO Regulator Board

Discussion in 'The Projects Forum' started by eyybro, Jul 22, 2013.

  1. eyybro

    Thread Starter New Member

    Dec 5, 2012
    Hello all,

    I'm doing a simple LDO regulator board-build as a power management IC practice. Please refer to the attached image for a relevant schematic.

    Originally, I intended on using an electrolytic capacitor for C1 to filter out noise and oscillations thereof. However, I could not find an electrolytic 0.12μF capacitor in my passive components kit, so I substituted with a ceramic capacitor.

    The diode seen in the schematic is there to prevent chip destruction from potential reverse current; an unknown brand 1N4004 has been placed there.

    The following link contains the datasheet for BA033T:


    I started analysis upon completion of the physical build, and I was able to attain data necessary to create an efficiency curve; however, the analysis entailed incrementally increasing the input voltage up to a certain point. Well, I obviously did not think things through when I was increasing the input voltage by 1V increments until I reached 12V, because when I reached 12V my board started exhibiting very chaotic, oscillatory current fluctuations until I quickly turned off the power supply. I immediately grounded all parts to rid the board of unwanted charge, and I tried to run 5V through the board. The board was designed to output 400mA at an input of 5V and an output of 3.3V with an efficiency of 90%~. My board now can ouput 400mA at an input of 0.84V. I had multiples of the same parts being used for my build, so I replaced every part considering the fact that I may have zapped a capacitor. This proved to be useless as I am still observing my board outputting 400mA at an input of 0.84V.

    Would anyone be so kind as to explain to me what I may have done incorrectly?

    Thank you!
  2. bertus


    Apr 5, 2008

    Do you use a large heatsink during your tests?

    This is written in the datasheet:

    A to high device temperature due to a to high dissipation can lead to this phenomena.

  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Agreed, at 12v in and 3.3v 400mA out, that little regulator was dissipating 3.48W. Then it died.
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    If it is an LDO, the output cap C2 will have ESR limits to maintain stability. Should be listed on the data sheet.