Hi.
I'm having trouble with the operation of a TPS63000 regulator. The output is a 'sawtooth' waveform. See the attached picture.
This data is taken from the 10uF cap directly at the output of the TPS63000. You can see that they sawtooth form has a frequency of ~1.35 kHz, and voltage extremes at 1.52 VDC, and 3.78 VDC. The output should be 3.3 VDC.
The first thing I noticed is the low switching speed. The load on the regulator should only be a few dozen mA. VIN is ~4.7VDC. The PS/SYNC pin is pulled high, as is shown in the Typical Application Schematic The layout does not follow the guidelines exactly, unfortunately. The inductor is 2.2 uH and located directly next to its pins on the IC.
The output caps are directly at the output, however, the input capacitor is a few inches away from the VIN pins. Could this be the problem? Is it getting current-staved somehow?
Also, when I bypass this regulator and apply an external 3.3VDC to the board, things seem to work fine (controller boots, and runs, etc), and current draw is reasonable. So, this issue does appear to be an issue with the regulator.
I appreciate your help. If it would help, I can be reached on the phone at 310-408-0273
Thanks, Steve