Hi,
Using TPS61151 to drive 6 LED on one of the two rows. We have a strange effect. If we disconnect the display (the string of 6 LEDs) the chip blows up. I can measure a low resistance approx. 37 ohms between SW and GND in both directions instead of MOhms on a non defective chip.
In another design with the same circuit and a similar layout the chip works as it should. On a scope you can see that the output voltage rises to OVP smoothly and then it is set to a low output voltage when the OVP conditions are reached.
How can I prevent the chip from dying?
What causes the chip to die?
It looks like the OVP is not fast enough to protect the cicuit inside the chip. Are parasitic oscillations able to kill the chip when the output voltage without load reaches the over protection voltage?
Does it make sense to add a R-C network from SW to GND to damp the parasitic oscillations? Would you recomment this?
Is a TPS61150 a better solution?
Best regards
L. Werres