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7534 FAIRCHILD | Alldatasheet

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Rev. A, July 2004©2004 Fairchild Semiconductor Corporation Abstract An empirical self-heating SPICE MOSFET model which accurately portrays the verti- cal DMOS power MOSFET electrical and thermal responses is presented. This macro-model implementation is the culmination of years of evolution in MOSFET modeling. This new version brings together the thermal and the electrical models of a VDMOS MOSFET. The existing electrical model [2,3] is highly accurate and is recog- nized in the industry. The sequence of the model calibration procedure using para- metric data is described. Simulation response of the new self-heating MOSFET model track the dynamic thermal response and is independent of SPICE’s global tem- perature definition. 1. Introduction Many power MOSFET models available today are based on an ideal lateral MOSFET device. They offer poor correlation between simulated and actual circuit performance in several areas. They have low and high current inaccuracies that could mislead power circuit designers. This situation is further complicated by the dynamic perfor- mance of the models. The ideal low power SPICE level-1 NMOS MOSFET model does not account for the nonlinear capacitive characteristics C iss, Coss, Crss of a power MOSFET. Higher level SPICE MOSFET models may be used to implement the non-linear capacitance with mixed results. The need for this higher level modeling accuracy becomes apparent in high frequency applications where gate charge losses as a proportion of overall losses become significant. The inherent inaccuracies of modeling a power VDMOS with the SPICE MOSFET model dictated the need for an alternative approach; a macro-model. A macro-model such as the one defined by Wheatley and Hepp [1] can address the short comings of the ideal low power SPICE MOSFET model. Highly accurate results are possible by surrounding a temperature independent gain block (implemented using three level-1 MOSFET models ) with resistive, capacitive, inductive and other SPICE circuit elements. Application Note 7534 A New PSPICE Electro-Thermal Subcircuit For Power MOSFETs Alain Laprade, Scott Pearson, Stan Benczkowski, Gary Dolny, Frank Wheatley July 2004

Rev. A, July 2004©2004 Fairchild Semiconductor Corporation It is possible to develop a model from parametric measurements in a single iteration. The model extraction procedure from parametric data must follow a given sequence. Many of the changes to the model affect different behaviour. Failure to follow this sequence will result in repeated model calibration iterations. The MOSFET model reference on which this work is based has been explained in [1, 2, 3, 10]. The reader is encouraged to refer to these references for a full understand- ing of the MOSFET model parameters herein referenced. Use of the model, once extracted is not discussed here, but reference [10] addresses the use. Recent works [8, 9] have demonstrated methods of circumventing the SPICE global temperature definition, providing a means of using the device’s own junction tempera- ture as a self-heating feedback mechanism. The model developed in [8] has limitations involving proprietary algorithms, rendering the method of limited interest. Model implementation is convoluted, involving a MOS- FET analog behavioral model (ABM) implementation whose operating characteristics are dependent on a SPICE level-3 NMOS MOSFET. As a result, both the switching circuit and the load must be duplicated for the model to function. The implementation in [9] does not model the drain-source avalanche property of a MOSFET. Neither [8] nor [9] attempt to model the temperature characteristics of the intrinsic body diode. Introduced self-heating modeling concepts are non-proprietary and may be adapted to other MOSFET models. 2. Self-Heating SPICE MOSFET Model The self-heating macro-model in Figure 1 is the evolution of years of work and improvements from numerous authors [1-7]. A significant advantage of this model is that knowledge of device physics or process details are not necessary to implement the parametric data within the model.

Figure 1. Self-heating MOSFET macro-model independent of global temperature definition operating junction temperature. instantaneous power dissipation to the thermal model. Multiple MOSFETs may be simulated at different and variable junction temperatures. the model in bridge topologies. rce terminals are no different than those of the standard MOSFET model.

Rev. A, July 2004©2004 Fairchild Semiconductor Corporation (1) where Tj = junction temperature, Pdissipation = instantaneous power loss, ZθJC = ther- mal impedance junction-to-case and Tcase = case temperature. The unite conversion for the electrical analog ofthe thermal system is listed in Table 1. Table 1 Electrical/thermal analogy 4. Parameter Extraction Methodology The sequence of the parameter extraction procedure is very important since many of the changes to the library affect differnt behavior. For instance, changing parameters in the transfer curve affect the saturation curves. The remcommended methodology is show below. 1. The transfer curve 2. The saturation curve 3. The body diode forward conduction 4. Breakdown voltage 5. T rr 6. Capacitance (Crss, Coss, Ciss) 7. Gate charge 8. Temperature coefficients 9. Thermal model Extraction is achieved more rapidly if data is plotted log-log, semilog, versus t, etc. First extraction may take days. It becomes a rapidly learned rocess with repeated usage. 4.1. Transfer Curve Three level-1 MOSFET transistors are used to model the gain block for the full current range from the sub-threshold region through high current. The three transistor mod- els are MweakMOD , MmedMOD and MstroMOD. The parameters VTO and KP of each transistor are used for alignment of the model with measured data. .MODEL MmedMOD NMOS ( VTO=3.3 KP=9 IS=1e-30 N=10 TOX=1 L=1u W=1u RG=1.36 T_ABS=25) .MODEL MstroMOD NMOS ( VTO=4.0 KP=275 IS=1e-30 N=10 TOX=1 L=1u W=1u T_ABS=25) caseJCndissipatioj TZPT +⋅= θ I Electrical Thermal Ohm oC/Watt Farad Joules/oC Amp Watt Volt oC

Rev. A, July 2004©2004 Fairchild Semiconductor Corporation .MODEL MweakMOD NMOS ( VTO=2.72 KP=0.03 IS=1e-30 N=10 TOX=1 L=1u W=1u RG=13.6 RS=0.1 T_ABS=25) Source resistance (G_Rsource) is added to lower the gain at high currents. It is also a contributing element to the device rDS(ON) . Plotting the square root of IDS versus VGS results in a linear curve instead of a quadratic curve, thus improving the visual resolution of the daa at the higher current range. G_Rsource 8 7 VALUE={V(8,7)/(2.5e-3*(1+5e-3*(V(th+)-25)+1e-6*pwr((V(th+)- 25),2)))} 4.2. Saturation Curves Several gate biases should be used to model the saturation curves. For instance, to model a standard gate device use V GS =10V, 5V and 3.5V. G_Rdrain is used to fit the model in the linear region. Increasing G_Rdrain will decrease the current of the satu- ration curves. Next, the space charge limiting effect is modeled using ESLC . The muliplier X in ESLC (1e-6*X, the exponent of the power statement) is adjusted. Low- ering X will round off the curves at high currents. If two saturation curves (for instance at Vgs=10V and Vgs=5V) do not match in the linear region, it may be necessary to readjust KP of the strong transistor MstroMOD . Modeling between transfer and satu- ration curves will then need to be repeated until both curves fit the data. G_Rdrain 50 16 VALUE={V(50,16)/(1e-4* (1+5.5e-2*(v(th+)-25)+3.2e-4*PWR((v(th+)- 25),2)))} ESLC 51 50 VALUE={(V(5,51)/ABS(V(5,51))) *(PWR(V(5,51)/(1e-6*300),10)))} 4.3. Body Diode Forward Voltage Match diode curve data at low currents by adjusting parameters IS and N in Dbody- MOD . With the forwardvoltage plotted on a log scale, N will adjust the slope and IS will shift the curve left or right. T_ABS=25) The high current region is modeled on the linear scale. G_Rdbody is used to match diode curve data at high currents by adding series resistance, thus lowering the curve. G_Rdbody 7 31 VALUE={V(7,31)/(1.65e-3* (1+2.7e-3*(V(TH+)-25)+2e- 7*PWR((V(TH+)-25),2)))} IKF can be used to smooth the transition region between low currents and high cur-

Rev. A, July 2004©2004 Fairchild Semiconductor Corporation rents. After changing IKF, it is often necessary to readjust G_Rdbody . XTI=3.9 IKF=100 T_ABS=25) 4.4. Breakdown Voltage Low current breakdown is modeled with Ebreak. Ebreak 11 32 VALUE={69.3*(1+9.5e-4* (V(TH+)-25)+1e-7*PWR((V(TH=)-25),2)))} High current breakdown is modeled with G_Rdbreak. G_Rdbreak 32 7 VALUE={v(32,7)/(7.0e-2* (1+5e-4*(V(TH+)-25)+1e-7* PWR((V(TH+)-25),2)))} 4.5. Trr Intrinsic body diode reverse recovery is modeled at 100A/µS and the maximum rated DC current. Parameter TT of the body diode DbodyMOD is used to match the mod- eled Ta to the mearsured Ta. XTI=3.9 T_ABS=25) 4.6. Capacitance Capacitance is moedled for drain-to-source voltages of 0.1V to the breakdown volt- age. Crss is modeled first, setting CJO and M of DplcapMOD . CJO will adjust the level of the capacitance curve while M will adjust the slope. Next Coss is modeled with CJO and M of DbodyMOD . This is done in a similar manner to Crss. Finally input capacitance Ciss is adjusted by setting Cin of the model. .MODEL DplcapMOD D (CJO=1.7e-9 IS=1e-30 N=10 M=0.47) XTI=3.9 T_ABS=25) Cin 6 8 6.1e-9 4.7. Gate Charge Modeling of the gate charge curve is a four step process (Figure 4). First, adjust the slope through the most negative gate voltages by adjusting Ca . Next, adjust the slope breakpoint by adjusting S1A and S1B switch voltages (VON and VOFF ) to account for

should be VOFF of S1BMOD , and vice versa). Figure 4. Modeling gate charge tion of the separation below 0.5V can result in convergence errors. Repeat steps 4.1 through 4.4 at a low and high temperature (ex. -25oC and 125oC).

Rev. A, July 2004©2004 Fairchild Semiconductor Corporation low currents adjust the temperature parameters of Evthres. The temperature coeffi- cients of G_Rsource may be used to fit the curve at high currents. The first parameter highlighted in each line below is a linear coefficient and the second is a square func- tion coefficent. Evtemp 20 6 VALUE={-2.5e-3*(V(TH+)-25) +1e-6*PWR((V(TH+)-25),2)} Evtemp 6 21 VALUE={-6.7e-3*(V(TH+)-25) -1.5e-5*PWR ((V(TH+)-25),2)} G_Rsource 8 7 VALUE={V(8,7)/(2.5e-3* (1+5e-3*(V(th+)-25)+1e-6*pwr((V(th+)- 25),2)))} Saturation Curves: First adjust the temperature parameters of G_Rdrain. Then model the temperature parameters of G_RSLC1 . This models the space charge limit- ing effect over temperature. G_Rdrain 50 16 VALUE={V(50,16)/(1e-4* (1+5.5e-2*(v(th+)-25)+3.2e-4*pwr((v(th+)- 25),2)))} G_RSLC1 5 51 VALUE={V(5,51)/(1e-6* (1+1e-3*(v(th+)-25)+1e-5*pwr((v(th+)- 25),2)))} Body Diode Forward Voltage: At low currents the forward voltage is modeled with the temperature coefficients of EDbody . The last parameter in EDbody is used to limit V f above 175oC. Thermal parameters of G_Rdbody are used to model the high current region. EDbody 31 30 VALUE={IF(V(TH+)<175,-1.5e-3*V(TH+)+.03,0.2325)} G_Rdbody 7 31 VALUE={V(7,31)/(1.65e-3* (1+2.7e-3*(V(TH+)-25)+2e- 7*PWR((T(TH+)-25),2)))} Breakdown voltage: Low current breakdown is modeled with thermal parameters of Ebreak. Thermal parameters of G_Rdbreak are used to model high current. G_Rdbreak 32 7 VALUE={v(32,7)/(7.0e-2* (1+5e-4*(V(TH+)-25)+1e-7*PWR((T(TH+)- 25),2))) Ebreak 11 32 VALUE={69.3*(1+9.5e-4*(V(TH+)-25)+1e-7*PWR((V(TH+)-25),2))) 4.9. Thermal Model The thermal model is modeled independently of the electrical model. Components CTHERM1 through CTHERM6 and RTHERM1 through RTHERM6 are used to fit the simulated thermal impedance curve to the measured data. To ensure a good thermal model, the thermal capacitors should be increasing in value from CTHERM1 through CTHERM6. Thermal resistors should also be increasing in value from RTHERM1 through RTHERM6.

voltage. Excellent agreement exists. Figure 5. FDP038AN06A0 threshold voltage Conditions: ID = 250µA

Rev. A, July 2004©2004 Fairchild Semiconductor Corporation the junction temperature feeback on the MOSFET temperature dependent parame- ters. 7. Future Model Developments Minor inaccuracy is introduced if previously published Fairchild Semiconductor MOS- FET models are modified to become self-heating models, but are well within device parametric tolerance (not demonstrated in this paper). The inaccuracy can be elimi- nated by including the variable T_ABS=25 in the level-1 NMOS MOSFET during device specific model calibration, permitting full compatibility of the model with the new self-heating model. This term was included for the standard MOSFET model cal- ibration of the FDP038AN06A0. Temperature dependency of the self-heating model intrinsic body diode leakage current could be introduced by adding a junction temper- ature dependent current source across the body diode. 8. Conclusion The self heating PSPICE power MOSFET macro-model provides the next evolution- ary step in circuit simulation accuracy. The inclusion of a thermal model coupled to the temperature sensitive MOSFET electrical parameters results in a self-heating PSPICE MOSFET macro-model which allows increased accuracy during time domain simulations. The effect of temperature change due to power dissipation during time domain simulations can now be modeled. The modeling modification concepts introduced are non-proprietary and may be adapted to MOSFET SPICE models from any manufacturer. A methodology for cali- brating a MOSFET model using parametric data was described. Adherence to the calibration sequence yields a highly accurate model. References [1] W.J. Hepp, C. F. Wheatley, “A New PSPICE Subcircuit For The Power MOSFET Featuring Global Temperature Options”, IEEE Transactions on Power Electronics Specialist Conference Records, 1991 pp. 533-544. [2] “A New PSPICE Subcircuit for the Power MOSFET Featuring Global Temperature Options”, Fairchild Semiconductor, Application Note AN-7510, October 1999. [3] S. Benczkowski, R. Mancini, “Improved MOSFET Model”, PCIM, September 1998, pp. 64-69. sentation for Power MOSFETs Using Empirical Methods,” RCA Review”, Vol 46, Sept 1985.

Rev. A, July 2004©2004 Fairchild Semiconductor Corporation ware For Power MOSFET Modeling,” Fairchild Semiconductor, Application Note AN7506, February 1994. Gate-Voltage Propagation Effects In Power MOSFETs”, Proc. HFPC, May 1986, p. 146. [8] F. Di Giovanni, G. Bazzano, A. Grimaldi, ”A New PSPICE Power MOSFET Subcir- cuit with Associated Thermal Waveforms of the L 2 FET: A 5Volt Gate Drive Power MOSFET”, Power Electronics Specialist Conference Model”, PCIM 2002 Europe, pp. 271-276. [9] M. März, P . Nance, “Thermal Modeling of Power-electronic Systems”, Infineon Technologies, Application Note, mmpn_eng.pdf. FET Model With Dynamic Temperature Compensation”; PCIM Shanghai 2003, p. 177.

Rev. A, July 2004©2004 Fairchild Semiconductor Corporation Appendix I Self-Heating MOSFET SPICE Model .SUBCKT FDP038AN06A0_5NODE 2 1 3 Tj Tcase Ca 12 8 1.5e-9 Cb 15 14 1.5e-9 Cin 6 8 6.1e-9 EDbody 31 30 VALUE={IF(V(Tj,0)<175,-1.5E-3*V(Tj,0)+.03,-.2325)} Dbody 30 5 DbodyMOD Dbreak 5 11 DbreakMOD Dplcap 10 5 DplcapMOD RDBODY 30 7 1E15 G_Rdbody 7 31 VALUE={V(7,31)/(1.65e-3*(1+2.7E-3*(V(Tj,0)-25)+2E- 7*PWR((V(Tj,0)-25),2)))} G_Rdbreak 32 7 VALUE={v(32,7)/(7.0e-2*(1+5e-4*(V(Tj,0)-25)+1e-7*PWR((V(Tj,0)- 25),2)))} Ebreak 11 32 VALUE={69.3*(1+9.5E-4*(V(Tj,0)-25)+1e-7*PWR((V(Tj,0)-25),2))} Eds 14 8 5 8 1 Egs 13 8 6 8 1 Esg 6 10 6 8 1 Evthres 6 21 VALUE={-6.7E-3*(V(Tj,0)-25)-1.5E-5*PWR((V(Tj,0)-25),2)} Evtemp 20 6 VALUE={-2.5e-3*(V(Tj,0)-25)+1e-6*PWR((V(Tj,0)-25),2)} Lgate 1 9 4.81e-9 Ldrain 2 5 1.0e-9 Lsource 3 7 4.63e-9 RLgate 1 9 48.1 RLdrain 2 5 10 RLsource 3 7 46.3 Mmed 16 6 8 8 MmedMOD Mstro 16 6 8 8 MstroMOD Mweak 16 21 8 8 MweakMOD G_Rdrain 50 16 VALUE={V(50,16)/(1E-4*(1+5.5E-2*(v(Tj,0)-25)+3.2E-4*pwr((v(Tj,0)- 25),2)))} Rgate 9 20 1.36 G_RSLC1 5 51 VALUE={v(5,51)/(1e-6*(1+1E-3*(v(Tj,0)-25)+1E-5*pwr((v(Tj,0)- 25),2)))} RSLC2 5 50 1e3 G_Rsource 8 7 VALUE={V(8,7)/(2.8E-3*(1+5e-3*(V(Tj,0)-25)+1e-6*pwr((V(Tj,0)- 25),2)))} S1a 6 12 13 8 S1AMOD S1b 13 12 13 8 S1BMOD S2a 6 15 14 13 S2AMOD S2b 13 15 14 13 S2BMOD ESLC 51 50 VALUE={(V(5,51)/ABS(V(5,51)))*(PWR(V(5,51)/(1e-6*300),10))} G_PDISS 0 TH+ VALUE={I(ESLC)*V(5,7) + I(EVTEMP)*V(9,7) + I(EBREAK)*V(5,7) + I(EDBODY)*V(7,5)}C THERM1 Tj 106 6.45E-3 CTHERM2 106 105 3e-2 CTHERM3 105 104 1.4e-2 CTHERM4 104 103 1.65e-2

Rev. A, July 2004©2004 Fairchild Semiconductor Corporation CTHERM5 103 102 4.85e-2 CTHERM6 102 Tcase 1e-1 RTHERM1 Tj 106 3.24e-3 RTHERM2 106 105 8.08e-3 RTHERM3 105 104 2.28e-2 RTHERM4 104 103 1e-1 RTHERM5 103 102 1.1e-1 RTHERM6 102 Tcase 1.4e-1 TT=1.0e-9 XTI=3.9) .MODEL DbreakMOD D () .MODEL DplcapMOD D (CJO=1.7e-9 IS=1e-30 N=10 M=0.47) .MODEL MmedMOD NMOS (T_ABS=25 VTO=3.3 KP=9 IS=1e-30 N=10 TOX=1 L=1u W=1u RG=1.36) .MODEL MstroMOD NMOS (T_ABS=25 VTO=4.0 KP=275 IS=1e-30 N=10 TOX=1 L=1u W=1u) .MODEL MweakMOD NMOS (T_ABS=25 VTO= 2.72 KP=0.03 IS=1e-30 N=10 TOX=1 L=1u W=1u RG=13.6 RS=.1) .MODEL S1AMOD VSWITCH (RON=1e-5 ROFF=0.1 VON=-4 VOFF=-1.5) .MODEL S1BMOD VSWITCH (RON= 1e-5 ROFF=0.1 VON=-1.5 VOFF=-4) .MODEL S2AMOD VSWITCH (RON=1e-5 ROFF=0.1 VON=-1 VOFF=.5) .MODEL S2BMOD VSWITCH (RON=1e-5 ROFF=0.1 VON=.5 VOFF=-1) .ENDS

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