Fairchild AN-7510 Data Handbook

A New PSPICE Subcircuit for the Power MOSFET

Featuring Global Temperature Options

October 1999 AN-7510

Abstract accepted by users, and the ease of parameter extraction should be demonstrated.

An empirical sub-circuit was implemented in PSPICE® and is presented. It accurately portrays the vertical DMOS power

/Title Method MOSFET electrical and for the first time, thermal responses. AN75 A sub-circuit approach is employed which is empirical. It is

Excellent agreement is demonstrated between measured

0) and modeled responses including first and third quadrant developed to provide black box conformity to the power MOSFET and gate charge behavior, body diode effects, MOSFET throughout the operating regime normally

breakdown voltage at high and low currents, gate equivalent traversed by the dictates of most power circuit applications

ect (A

series resistance, and package inductances for including junction temperature. Although device thermal

ew behavior is the driving force, respect is maintained toward temperatures between -55o C and 175o C. Parameter extrac-

spice tion is relatively straight forward as described. the physics and the SPICE algorithms. ubcir- The developed sub-circuit schematic is shown in Figure 1.

Introduction uit There are many forms of SPICE, each with its own strengths Circuit simulation commonly uses one of the SPICE [1] and weaknesses. PSPICE was chosen for the following

or programs. However, power circuits require proper models for reasons. he unique devices which are not included in the supplied librar- 1. An evaluation copy capable of considerable circuit analy- ower ies. Efforts have been published to model the power MOS- sis for power circuits is available.

OS- FET [2-10] with varying degrees of success. The more

2. The PROBE feature provides excellent displays.

successful papers have used sub-circuit representation. To

ET 3. Programmed time slice defaults and DC convergence

date, a thermal model has not been offered.

eatur- routines make it very friendly.

ng Objective 4. The switch algorithm of PSPICE provides a very smooth

transition from off to on.

lobal It is the goal of this effort to provide for the first time a

thermal sub-circuit model capable of providing accurate sim- Other forms of SPICE were not investigated, but they should

ulation throughout all of the power MOSFET regimes. In be amenable to the development of a similar sub-circuit by

addition the sub-circuit should be readily understood and paralleling the teachings of this work.

ure ption

DRAIN

Autho

DPLCAP LDRAIN

RDRAIN

ESG 6/8

Key- DBREAK

ords VTO

Inter- EVTO DBODY

GATE RGATE

18/8 MOS1

EBREAK

orpo- LGATE 17/18

RIN CIN

ation,

RSOURCE LSOURCE

SOURCE

RBREAK

uctor

S2BS1B CB

CA 19IT

tor ()

DOC EGS EDS VBAT

NFO df-

FIGURE 1. PSPICE MODEL SUBCIRCUIT

©2002 Fairchild Semiconductor Corporation Application Note 7510 Rev. A1