SafeDemag is a feature used for inductive load applications in particular. For the majority of industrial applications, engineers use a high-side switch to control the inductive load, and the challenge is how to discharge the energy in the inductor when the switch opens and the current is no longer sourced to the load. The negative impacts of not discharging this energy correctly include potential arcing of relay contacts, large negative voltage spikes damaging sensitive ICs, and the generation of high frequency noise or EMI that can affect system performance.
During fast demagnetization mode the current is controlled by the energy in the load, so no protection (current or temperature) is active during this mode. To solve the issue of excessive energy dissipation during fast demagnetization and the thermal issues of the MOSFET, Maxim has implemented the new SafeDemag feature in the MAX14912 and MAX14913 Octal High-Speed Switch products. SafeDemag works in conjunction with the fast demagnetization circuitry and allows the MAX14912 and MAX14913 to safely turn off loads with unlimited inductance. Under normal turn-off, the high-side MOSFET works in linear mode to dissipate the inductor energy using the fast demagnetization feature. If the energy in the inductor, and hence the demagnetization current is too high, the high-side MOSFET begins to overheat. At this point, an on-chip temperature sensor alerts the control logic to turn off the high-side MOSET and turn on the low-side MOSFET providing a low voltage (and hence low power) alternative path for the demagnetization current, allowing the high-side MOSFET to cool and return to safe operating limits.