EM6151

R EM MICROELECTRONIC - MARIN SA EM6151 Low Power Windowed Watchdog with Reset, Sleep Mode Functions Description The EM6151 offers a high level of integration by combining voltage monitoring and software monitoring using a windowed watchdog. A comparator monitors the voltage applied at the VIN input comparing it with an internal voltage reference VREF. The power-on reset function is initialized after VIN reaches VREF and takes the reset output inactive after a delay TPOR depending on external resistance ROSC. The reset output goes active low when the VIN voltage is less than VREF. The RES and EN outputs are guaranteed to be in a correct state for a supply voltage as low as 1.2 V. The watchdog function monitors software cycle time and execution. If software clears the watchdog too quickly (incorrect cycle time) or too slowly (incorrect execution) it will cause the system to be reset. For enhanced security, the watchdog must be serviced within an “open” time window. During the remaining time, the watchdog time window is “closed” and a reset will occur should a TCL pulse be received by the watchdog during this “closed” time window. The ratio of the open/closed window is either 33%/67% or 67%/33%. The system ENABLE output prevents critical control functions being activated until software has successfully cleared the watchdog three times. Such a security could be used to prevent motor controls being energized on repeated resets of a faulty system. When the microcontroller goes in...