Why is a series resistor on VDD line needed for SPOC™+2 devices?
There are three main reasons for putting a VDD resistor into the VDD line:
1. When the system is reverse-supplied, there will be a current flow from microcontroller into VDD pin of the device. To stay within the maximum ratings, a series resistor has to be placed.
2. Transients on the battery could cause a positive or negative ground shift, which leads to a current flow through VDD pin. To limit the current during this application condition, a series resistor is recommended.
3. A series resistor will protect the digital supply in case of a fault condition at VDD pin when shared with other devices. Examples for fault conditions are external short circuit to ground on VDD pin or internal faults which lead to a high current consumption on VDD.