External watchdog helps to reduce common mode failure, as it utilizes clock, reset, and power that are separate from the system being monitored. Error response, diagnostic testability, and any necessary software requirements are defined by the external watchdog selected by the system integrator.

Texas Instruments highly recommends the use of an external watchdog in addition to the internally provided watchdogs. An internal or external watchdog can provide an indication of inadvertent activation of logic which results in impact to safety critical execution. Any watchdog added externally should include a combination of temporal and logical monitoring of program sequence [IEC61508-7, clause A.9.3] or other appropriate methods such that high diagnostic effectiveness can be claimed.