I am using the TIOS101 (no internal LDO) in a circuit where the VCC_IN can be un-powered and VCC pin can be powered or vice versa.
I noticed that when VCC_IN is un-powered and the VCC pin is powered (24V), the VCC_IN pin continually switches on/off. It back feeds current into my un-powered 5V circuit lifting the voltage to about 3V (even with a 500 Ohm resistor connected across from VCC_IN to GND). It seems like the TIOS101 exits the UVLO state and then the voltage on VCC_IN starts ramping down to 1.5V and then it repeats.
The TDS states that: "VCC_IN and VCC domains can be powered up in any sequence. In the event of VCC is powered and VCC_IN is
not, the OUT pin remains in high impedance."
The output seems to be in high Z under this condition because the enable pin is low, but why is the VCC_IN pin back feeding current into my circuit?
Bart