• Resolved

PTH12040 high output noise at certain voltages/currents

I'm evaluating PTH12040WAH and found strange behavior of output voltage. It shows relatively large voltage oscillation/fluctuations just at some output votlages & currents.


This output around 1.6V 4A. The signal is AC coupled to view only ripple. Also notice the time scale, it's not switching ripple but regulation ripple.


And this about 1.7V 4.5A


The filter capacitors are certainly sufficient (I have tried many different sizes & configurations but the result always same).

*Input caps are 2-3 pcs 470 uF 10mOhm ERS poly aluminium

*Output caps 1-3 pcs 1200 uF 10mOhm ERS poly aluminium

*Output load is two high current silicon diodes in series (just for testing)

*Voltage adjustment with trimpot


What could be wrong or is this normal?

  • The PTH12040  is limited  to no more than < 4mΩ ESR total , in parallel  on the output bus.The 1200uF 10mΩ capacitors  x 3 combined parallel ESR, is less tahn 3.3mΩ.

    My e-mail  address is tguerin@ti.com. Send me an e-mail and we can discuss this comment.