Gates rated at 12 V will likely succumb at about 15 V or so gates having a 20-V rating typically fail at around 25 V.Īll in all, exceeding the MOSFET voltage rating for just a few nanoseconds can destroy it. For example, a suitably high voltage applied between the gate and source (V GS ) will break down the MOSFET gate oxide. ![]() A common outcome of a direct short is a melting of the die and metal, eventually opening the circuit. In this case, only the source impedance of the power source limits the peak current. Optimized for on/off switching, they typically don’t work well in their linear region.Ī typical failure mode for a MOSFET is a short between source and drain. But MOSFETs designed for switch-mode power supplies can experience a wide temperature variation over different areas of their die. One factor to consider in this regard is that MOSFET thermal resistance is an average it applies if the whole die is at a similar temperature. Both 40- and 60-V devices are rated to operate at junction temperatures up to 175° C to facilitate greater thermal headroom for designs. These are complemented by NTMFS5C604NL, NTMFS5C612NL and NTMFS5C646NL models, which have breakdown voltage ratings of 60 V. Examples include NTMFS5C404NLT, NTMFS5C410NLT and NTMFS5C442NLT MOSFETs from ON Semiconductor, which have maximum R DS(on) values of 0.74, 0.9 and 2.8 mΩ respectively. New generations of MOSFETs incorporate features that include a low R DS(on) to minimize conduction losses and improve operational efficiency. But there are a variety of conditions that may cause high thermal gradients that may lead to expansion and cracking of the MOSFET die. The SOA graph, for example, generally assumes an ambient temperature of 25° C with a specific junction temperature, usually below 150° C. But it turns out, other thermal limits can apply. Basic values for the upper maximum on these parameters are given in the safe operating area (SOA) graph in the MOSFET datasheet. There is also a power limit given by the maximum junction temperature. ![]() Obviously, V gs and V ds must both be within limits. ![]() However, if not appropriately handled and protected, the high input impedance and gain can also lead to MOSFET damage caused by over voltage or too-high current.įirst a few basics about avoiding MOSFET damage. MOSFETs boast a high input gate resistance while the current flowing through the channel between the source and drain is controlled by the gate voltage. The MOSFET (metal-oxide-semiconductor field-effect transistor) is a primary component in power conversion and switching circuits for such applications as motor drives and switch-mode power supplies (SMPSs).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |