Hello,
I designed a circuit that operates on 3.5V and since it is powered with a single cell LiPo battery (3.0-4.1V) I decided to use TPS61200 as a power regulator.
After playing around in Webench simulations I made a 4-layer pcb (second layer as a GND layer) following the TPS61200 layout recommendations.
Unfortunatelly, the very first time I connected a battery and measured the output voltage from the power regulator I got a very high value, around 6.1V (instead of 3.5V). Voltage on FB pin (test point 2 on my schematic) was around 870mV instead of 500mV! Using an external power supply (with the same range as above) instead of a lipo battery generated the same output voltage.
I tried with different values on external divider resistors (on the same board) - the only difference was that sometimes the output voltage was around 1V (short circuit on output?).
The undervoltage protection is set to 3.3V. The voltage on the UVLO pin (test point 3) is above 250mV for all input voltages above 3.3V. When the UVLO pin drops below 250mV, the output voltage remains high (6.1V).
I cannot figure out what makes the output voltage so high. If there is a short circuit somewhere where should I start searching it for? Or maybe I just made a bad pcb component layout?
Thank you for your help.
