Tool/software:
Hello,
I have a basic TPS2121 for a power selection application between a 9V wall-wart power supply and a 7.2V NiMH battery pack. It is working fine, properly switching from IN1 to IN2. However, when IN1 is disconnected and the unit is powered from IN2, there is a voltage present on IN1 that is equal to IN2. This results in excessive current flowing out of the battery when the power supply is unplugged from the wall, because when depowered, power supplies tend to have a low impedance path across their terminals.
With the board totally removed from power and disconnected from everything, I measured approximately 20kOhms between IN1 and IN2. However, in operation we're seeing around 100mA of back flow current.
How can we ensure that when the circuit is powered from IN2, that no current is back fed to IN1?
Thanks,
Derek
