Dear TI technical support:
Good afternoon!
We used a TPS54335ADDAR DCDC step-down chip on our project. The circuit schematic and PCB are shown below. The input voltage is 9.7V and the output voltage is 7.7V. When we used it, we found that the PH pin is easy to short to the ground, and it will soon be short-circuited and burned out. It will appear after the instrument has been used for a long time.
What happened:
- Each time the chip is damaged at power-on, or when its load is enabled. The load current is 170mA. At the time of power-on, the load is disabled and the current is 0mA, which needs to be controlled by the MCU.
- We also have another same circuit in parallel with this circuit, which is the same input, the output is 5V. The difference is that the other circuit load is always there and does not require MCU control. We consider that there may be problems when without load.
- There is a slow start circuit at the front stage of these two circuits. And tested with an oscilloscope, there is no surge impact.
- After a certain period of use, the PH pin will be shorted to ground, and the internal lower MOS tube may be burned. The situation is the same every time, but the time of appearance is uncertain.
- We saw a few questions on your forum that are very similar to ours. The links are as follows:
https://e2echina.ti.com/question_answer/analog/power_management/f/24/t/157973
Our questions:
- What are the possible reasons for this problem? Are there any optimization methods?
- Since this problem was found late, our instrument has already started mass production, so is there a pin corresponding replacement chip?
Thanks a lot.
