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2020.05.27 Si Power Device

Terminology Relating to MOSFET Specifications

Si Transistors

Up till now, the features and characteristics of MOSFETs have been explained. Specifications (data sheets) describe the electrical specifications ("specs") for MOSFETs and other components, and list parameter names as well as guaranteed values and the like. MOSFETs have many parameters, a number of which have already been considered in these articles; here they are listed in summary.

There are points to be noted. There may be some differences among manufacturers in the parameter names, terminology, and symbols. Moreover, there are some differences relating to condition settings and definitions. These differences must be dealt with by checking the measurement conditions and other matters described in the data sheet and understanding the specific details of each component.

● Absolute Maximum Ratings

Parameter Symbol Definition and Description
Drain-source voltage VDSS The maximum value of the voltage that can be applied across the drain and source with the gate and source put into a short-circuit state.
Drain current (direct) ID The maximum value of the direct current that can flow continuously in the channel formed between the drain and source under specified conditions.
Drain current (pulse) IDP The maximum value of the current that can flow in pulses in the channel formed between the drain and source, for a pulse width and duty ratio specified by the safe operating area.
Gate-source voltage VGS The maximum value of the voltage that can be applied across the gate and source.
Avalanche current (single pulse) IAS The maximum value of the drain current that is allowed during avalanche breakdown.
Avalanche energy (single pulse) EAS The maximum value of the energy that is allowed during avalanche breakdown.
Power dissipation PD The maximum value of the power dissipation allowed in the MOSFET under specified conditions.
Junction temperature Tj The maximum value of the junction temperature that is allowed during component operation.
Storage temperature Tstg The temperature range within which the device can be stored or transported without applying an electrical load to the component.

● Thermal Resistance

Parameter Symbol Definition and Description
Thermal resistance (junction – case) RthJC The thermal resistance value from the device junction to the rear surface of the case.
Thermal resistance (junction – ambient) RthJA The thermal resistance value from the device junction to the ambient environment.
Soldering temperature (wave soldering) Tsold The maximum value of the solder melting temperature when mounting a MOSFET.

● Electrical Characteristics

Parameter Symbol Definition and Description
Drain–source breakdown voltage V(BR)DSS In the state in which the gate and source are short-circuited, the voltage at which breakdown of the parasitic diode occurs and a current begins to flow between the drain and source.
Drain–source breakdown voltage temperature coefficient ⊿V(BR)DSS/⊿Tj The temperature coefficient of the drain-source breakdown voltage.
Zero gate voltage drain current IDSS The leakage current that flows between the drain and source when the gate and source are short-circuited under specified conditions.
Gate leakage current IGSS The leakage current that flows between the gate and source when the drain and source are short-circuited under specified conditions.
Gate threshold voltage VGS(th) The gate-source voltage at which a drain current begins to flow in the MOSFET.
Gate threshold voltage temperature coefficient ⊿VGS(th)/⊿Tj The temperature characteristic of the gate threshold voltage.
Drain–source ON resistance RDS(on) The value of the resistance between the drain and source when the MOSFET is turned on.
Gate resistance RG The internal gate resistance value of the MOSFET.
Forward transfer admittance |Yfs| The rate of change in the drain current with a 1 V change in the gate-source voltage.
Input capacitance Ciss The value of the parasitic capacitance between the gate and source, measured in the state in which the drain and source are short-circuited for alternating currents.
Output capacitance Coss The value of the parasitic capacitance between the drain and source, measured in the state in which the gate and source are short-circuited for alternating currents.
Feedback capacitance Crss The value of the parasitic capacitance between the drain and gate, measured with the source pin grounded.
Effective capacitance (referred to energy) Co(er) The fixed capacitance value equivalent to the Coss value resulting in the energy accumulated from when the drain-source voltage VDS is 0 V until VDS rises to 80% of the absolute maximum rating of the drain-source voltage.
Effective capacitance (referred to time) Co(tr) The fixed capacitance value equivalent to the Coss value resulting in the charging time from when the drain-source voltage VDS is 0 V until VDS rises to 80% of the absolute maximum rating of the drain-source voltage.
Turn-on delay time td(on) The time from when the gate-source voltage has risen to 10% of a voltage setting until the drain-source voltage has fallen to 90% of a set voltage.
Rise time tr The time required for the drain-source voltage to fall from 90% to 10% of a voltage setting.
Turn-off delay time td(off) The time from when the gate-source voltage has fallen to 90% of a voltage setting until the drain-source voltage has risen to 10% of a set voltage.
Fall time tf The time required for the drain-source voltage to rise from 10% to 90% of a voltage setting.

● Gate Charge Characteristics

Parameter Symbol Definition and Description
Total gate charge Qg The amount of gate charge necessary to raise the gate voltage of the MOSFET from 0 V to a specified voltage.
Gate–source charge Qgs The amount of charge accumulated on the capacitance between the gate and source that is necessary to raise the gate voltage of the MOSFET from 0 V to the gate plateau voltage.
Gate–drain charge Qgd The amount of charge accumulated on the capacitance between the gate and drain that is necessary for the MOSFET drain-source voltage VDS to fall from the power supply voltage to the ON voltage.
Gate plateau voltage V(plateau) The value of the gate voltage at which mirror capacitance charge/discharge begins during switching.

● Internal Diode Electrical Characteristics

Parameter Symbol Definition and Description
Source current (direct) Is The maximum value of the direct current that can flow through the internal diode continuously under specified conditions.
Source current (pulse) Isp The maximum value of the current that can flow in pulses in the internal diode.
Forward voltage VSD The drop in voltage when a forward current has flowed in the internal diode.
Reverse recovery time trr The time required for the reverse recovery current in the internal diode to vanish under specified measurement conditions.
Reverse recovery charge Qrr The amount of charge required for the reverse recovery current in the internal diode to vanish under specified measurement conditions.
Peak reverse recovery current Irrm The value of the peak current during reverse recovery operation of the internal diode under specified measurement conditions.

Key Points:

・In some cases parameter names, terminology, and symbols may be somewhat different for different manufacturers.

・There are also some differences relating to definitions pertaining to condition settings.

・These differences must be dealt with by confirming the measurement conditions and other matters described in specifications, and understanding the specific details of components.

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