On about 20% of our new devices using the TPS65721 we see a problem with the shutdown process that results in an immediate and unwanted re-start of the PMU. During battery-powered operations we turn on the device with PB_IN, and then our microprocessor pulls high the HOLD_DCDC1 and HOLD_LDO1 pins (tied together at one output). Our design requires the device to automatically shut itself off after 30 seconds of inactivity, and we accomplish that by bringing the HOLD lines low. This works 100% of the time on about 80% of our devices, but fails consistently on the other 20%. An interesting observation is that if we hold PB_IN low during the shutdown (by pressing our "on" button), and then let up on it then the shutdown works (it stays "off"). Also, all register values are at default settings. Any insight into this issue would be greatly appreciated.
