Original question:
TPS61088: TPS61088 output voltage drops and does not recover
We used TPS61088 to convert 3.3V to 6.55V, and the schematic was generated using WEBENCH Power Designer. Another step-down DC/DC powered from 6.55V, total load less than 3W(measured at the 3.3V input).
After working continuously for more than 12 hours, the output suddenly drop to ~2.89V and does not recover. The output will return to normal after power cycle.
We have had this issue on two devices. Can someone help me?
This is the schematic we used. Rcomp is 28.7k, Ccomp is 1nF. Webench shows the Phase Marg is 52.39.
The SW is fixed at 3.3V when the fault occurs, not periodic. When we test with an electronic load, the SW is periodic even under overload. The actual typical load is 3.5W, and the maximum is 5W. To leave some margin, 1A load current was selected when using Webench.
EN is connected as follows, so it's always ~1.7V.
When the fault occurs, SS voltage is 1.2V, which may be a problem. What will cause it? We connect SS to ground through a 0.1uF capacitor.
Hi, Jasper
Thank you.
Failure takes a long time (two to four days) to occur, and only occurs at high temperatures above 40 degrees Celsius, and cannot be recovered even when the temperature drops to 25 degrees.
The board did not work after overload, I will try to toggle EN after fix it.
Fb drops to ~0.58V (the voltage measured by oscilloscope is a little high, actually it should be a little lower when measured by multimeter).The next time when it occurs, I'll use a better oscilloscope.
FB waveform:
Hi, Jasper
If the inductor is saturation, will the DC/DC not work, or just unstable?
The inductor MPN is LPS6225-102M, Irms@40°C = 1.65A. The 3.3V input current is 0.9A, this may cause the inductor to saturate.
