Maintain thermal stability for power-MOS devices

摘要

POWER MOSFETs can EXPERIENCE DESTRUCTIVE THERMAL EFFECTS AT RELATIVELY LOW DRAIN VOLTAGES AND CURRENTS THAT ARE WELL WITHIN TRADITIINAL. SAFE BOUNDARIES. HOWEVER DESIGNERS CAN USE BASIC SPICE-MODEL PARAME-TERS TO PREVENT THERMAL INSTABILITY IN THESE DEVICES. Power MOSFETs can experience destructive thermal effects at relatively low drain voltages and currents that ate well within the traditional SOA (safe-operating-area) boundaries. For typical SOA curves, in which gate-to-source voltage is larger than the threshold voltage, the increasing on-resistance of the MOS device dominates and effectively limits thermal runaway. Destructive failure can result, however, if the device is biased at a low gate-to-source voltage, such that sensitivity to the decreasing threshold voltage overwhelms the increasing channel resistance as temperature rises. You can use basic Spice-model parameters to estimate the minimum gate drive to prevent thermal instability and resultant damage to the device.