#Power mosfets plus#

Power semiconductor manufacturers include a curve in their power transistor data sheets ( Fig. Safe Operating Area, SOA, is a function of the voltage and current applied to the MOSFET. In the pulsed mode the pulse width and duty cycle determine safe drain current and device power dissipation. When operated in the pulsed mode, the MOSFET’s drain current can be several times its continuous rating. Rated Drain Current, I D, reflects the ability of the MOSFET to drive a specific load. In some cases, a heat sink may be required to maintain the device junction temperature below its maximum rating. The lower the thermal resistance, the more efficient the package is in eliminating heat. Data sheets rate thermal resistance in terms of either ☌/W or K/W. The junction-to-ambient and junction-to-case thermal resistance is a measure of the MOSFET’s ability to extract heat. Package thermal properties determine its ability to extract heat from the die. Maximum junction temperature, T J(max), is a function of the electrical characteristics of the device, as well as the package employed. Fig 2 shows the variation of R DS(ON) with junction temperature for V GS = 4.5 V and 10 V. In virtually all MOSFETS, the n-channel versions have lower on-resistance than p-channel devices with the same operating voltages. In many applications, the low on-resistance also eliminates the need to parallel MOSFETs for low on-resistance, which leads to improved reliability and lower overall system cost than previous MOSFET generations. Low on-resistance drastically reduces heat-sinking requirements in many applications, which lowers parts count and assembly costs. The lower the on-resistance, the lower the device power loss and the cooler it will operate. On-Resistance, or R DS(ON), determines the power loss and heating of the power MOSFET. 1 plots single pulse avalanche energy for a MOSFET.

And, the trench technology allows 10% lower on-resistance temperature coefficient. Trench power MOSFET technology provides 15% lower device on-resistance per unit area than existing benchmark planar technologies but usually at the cost of higher charge.

Trench technology provides the desirable characteristics of low on-resistance sometimes at the expense of high avalanche energy. Some devices are rated in terms of EAR, the repetitive avalanche energy. The higher the EAS, the more rugged the device. To ensure satisfactory performance, devices in this technology can be fully characterized for single pulse avalanche energy (EAS) up to their maximum junction temperature. Trench technology offers an avalanche capability approaching industry-leading planar technology. A second failure mode is thermal, which occurs if the avalanche condition raises the device temperature above its maximum junction temperature. The most destructive is “bipolar latching” that occurs if the device current causes a voltage drop across its internal device resistance, resulting in transistor action and latching of the parasitic bipolar structure of the MOSFET. The avalanche condition can cause two possible failure modes that can destroy a MOSFET. The higher the avalanche value, the more rugged the device.

Avalanche occurs if the maximum drain-to-source voltage is exceeded and current rushes through the device.

With inductive loads, the voltage across the MOSFET can actually be twice the applied voltage.Īvalanche Characteristics determine how much energy the MOSFET can withstand under avalanche conditions.

#Power mosfets plus#

When driving an inductive load, this includes the applied voltage plus any inductively induced voltage. Following are the characteristics associated with power MOSFETs.īlocking Voltage is the maximum voltage that can be applied to the MOSFET. Their current conduction capabilities are up to several tens of amperes, with breakdown voltage ratings (B VDSS) of 10V to over 1000V. Power MOSFETs (Metal-Oxide Semiconductor Field Effect Transistors) are three-terminal silicon devices that function by applying a signal to the gate that controls current conduction between source and drain.