EM Microelectronic has introduced the EM6151, a microprocessor voltage supervisory IC with programmable reset threshold voltages and a watchdog timer with programmable time window and system enable output.
Housed in an S08 and drawing 35 uA quiescent current, the EM6151 features an open drain reset output and operates over the -40 degree C temperature to +125 degree C temperature range. In automotive applications, it can be used to monitor the microprocessors that control electronic cockpit security and the steering column as well as trunk closure systems, electrical spoiler control and electrical seat, dashboad, sunroof, rear-view mirror and window controls.
The device's time-windowed watchdog function is said to recognize more faults than standard watchdog, which are dependent on CPU hardware and software to generate a counter reset signal. The windowed watchdog ensures that the timer clear signal occurs within the correct time window ("opened window) or else it activates a system reset or other error handling.
Watchdog timings are programmable using an external resistor to set the power-on reset delay and the watchdog time but the ratio for the close/open watchdog window is factory programmable. The EM6151V53 and EM6151V50 come with 67% and 33% opened watchdog windows respectively, with the smaller window providing greater security. The EM6151V55 offers a CAN bus sleep mode detector, so a CPU can issue a general "sleep" instruction to all EM6151V55-equipped peripheral modules, reducing the rate at which they generate reset signals but also reducing power drain when the system is off and extending battery life.
Reset threshold voltage is programmable using an external two-resistor voltage divider.