Dear TI engineer:
Hello!
I am switching power supply module PTH08T220WAD debug some problems, especially to you ask for advice.
Shown in Figure 1, which is switching power supply module PTH08T220WAD in my circuit board design, R254 for the sampling resistor, not welded at the beginning of debugging.
Plus +12 V voltage, switching power supply module PTH08T220WAD immediately issued a "Zizi" sound, measured output 9V, sometimes change the value, not a word I want to +1.2 V.
To +5 V input voltage, switching power supply module PTH08T220WAD sometimes issue "Zizi" sound, sometimes no hair, no hair The sound output when the voltage is correct for the +1.2 V.
Taking into account the more difficult welding to take the board down, I direct another film on switching power supply module PTH08T220WAD die test, shown in Figure 2.
Test Results and Figure 1, the only pin voadj missed resistance, the correct output voltage value of 0.7V.
I wonder if my circuit design problem, or what specific input voltage requirements, or chip problem, so I do not think their solution, ask for your help!
Hi Bin Jiang,
Please send a waveform of the output voltage during this condition.
Also, please remove R254 and replace with a short during your testing.
What is the ESR of the output capacitors you are using?