Hello expert,
I cut off the MCU SPI wire to make the TPS92520 enter limp home mode, and then I cut off the UDIM wire between MCU and TPS92520 so the UDIM PIN of TPS92520 is floating, noting connected. I find the output current is right as I set to NVM, and the voltage of UDIM is 3.8V. What is the internal circuit of the UDIM PIN? Why it can keep high voltage level although there is no external pull up?
Hello expert,
Yes I am sure. The UDIM is only connected by MCU IO, and during my test, I cut off the UDIM wire from MCU to 92520. So in this situation UDIM of 92520 is floating.
Hello Zhiyuan,
The UDIM pin is an input and the voltage is likely due to leakage from the part or external circuitry. Generally speaking, you should not leave an input floating. What where you expecting to see?
I have confirmed there is no pullup or pulldown resistors on UDIM. We do have a constant current source that turns on if the UDIM voltage goes above 1.22V. That provides the hysteresis for the enable/disable. If they leakage brings the voltage above 1.22V then that kicks in. This is in the functional block diagram, see below:
-fhoude
