Hello,
I am currently troubleshooting a prototype that utilizes a TPS61027 to boost 3.7V from a single Li-polymer cell to 5VDC. I chose the TPS61027DRCR for its fixed regulation and used the example schematic in Figure 25. I am observing an unstable output voltage when using a bench power supply as the input as well as a freshly charged Lithium cell. The output voltage on startup goes to 5 Volts DC, then the current draw steadily rises by a few mA, then the output voltage will drop to 4 Volts, then as the current begins to rise again the voltage slowly tapers off. I have noticed that the inductor is being switched until the output voltage drops below 4 volts, at which point the voltage on the inductor goes to the battery voltage and is no longer switching. I have tried cooling the part with freezer spray, and that produces a clean 5V output with no load current draw of 1-3mA, but once the part warms up, the same behavior starts. Below are some screen shots of what I am observing.
5 Volt output, and the voltage waveform on the inductor (6.8uH)
same image, showing low frequency oscillation on the inductor
