Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/ Semiconductor Device Modeling and Characterization – EE5342 Lecture 16 – Spring 2011 Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/

SPICE Diode Temp. Eqs.1 ©rlc L16-07Mar2011

Corrections in some versions of SPICE ©rlc L16-07Mar2011

SPICE Diode Temp. Pars.1 PARAMETER definition and units default value XTI IS temperature exponent 3.0 TIKF ikf temperature coefficient (linear) °C -1 0.0 TRS1 rs temperature coefficient (linear) °C -1 0.0 TRS2 rs temperature coefficient (quadratic) °C -2 0.0 TBV1 bv temperature coefficient (linear) °C -1 0.0 TBV2 bv temperature coefficient (quadratic) °C -2 0.0 T_ABS absolute temperature °C T_MEASURED measured temperature °C T_REL_GLOBAL relative to current temperature °C T_REL_LOCAL Relative to AKO model temperature °C ©rlc L16-07Mar2011

Thermal Resistance ©rlc L16-07Mar2011

Self-Heating Effects Id (A) Vd,ext = Vd + Id*RS 348K < TNOM < 300K 10 mW 20 mW 30 mW 40 mW 50 mW 60 mW 70 mW 80 mW Rth = 0 K/W , RS = 0.32 W Rth = 600 K/W, RS = 1 W ©rlc L16-07Mar2011

Self-Heating Effects SPICE models the IS, etc. the same for all power dissipations. The effect of diode self-heating is to increase the current at all voltages. In this case, an Rth of 600K/W gave nearly the same simulation as re-setting RS from 1 Ohm to 0.32 Ohm. The diode Tj is different at all curr. ©rlc L16-07Mar2011

PiN Diode PiN: Na >> Nint (= N-) & Nint << Nd Wi = Intrinsic region (metall.) width Em,P-T = Peak field mag. when xn = Wi Vbi = fi = Vtln(NaNd/ni2) Vbi,int = fi,int = Vtln(NaNint/ni2) VHL = Vtln(Nd/Nint), the offset at N+N- Vbi = Vbi,int + VHL VPT = applied voltage when xn = Wi ©rlc L16-07Mar2011

PiN Diode Depletion Fields Normalized Position, x’ = x/Wi Normalized Field, E/Em,P-T dx’p dx’n x’n -x’p ©rlc L16-07Mar2011

PiN Diode Depletion Conditions ©rlc L16-07Mar2011

CV data and N(x) calculation ©rlc L16-07Mar2011

Diode Switching Consider the charging and discharging of a Pn diode (Na > Nd) Wd << Lp For t < 0, apply the Thevenin pair VF and RF, so that in steady state IF = (VF - Va)/RF, VF >> Va , so current source For t > 0, apply VR and RR IR = (VR + Va)/RR, VR >> Va, so current source ©rlc L16-07Mar2011

Diode switching (cont.) VF,VR >> Va F: t < 0 Sw RF R: t > 0 VF + RR D VR + ©rlc L16-07Mar2011

Diode charge for t < 0 pn pno x xn xnc ©rlc L16-07Mar2011

Diode charge for t >>> 0 (long times) pn pno x xn xnc ©rlc L16-07Mar2011

Equation summary ©rlc L16-07Mar2011

Snapshot for t barely > 0 pn Total charge removed, Qdis=IRt pno x xn xnc ©rlc L16-07Mar2011

I(t) for diode switching ID IF ts ts+trr t - 0.1 IR -IR ©rlc L16-07Mar2011

References 1Semiconductor Device Modeling with SPICE, 2nd ed., by Massobrio and Antognetti, McGraw Hill, NY, 1993. **OrCAD Pspice A/D Reference Guide, Copyright 1999, OrCAD, Inc. ***MicroSim OnLine Manual, MicroSim Corporation, 1996. ©rlc L16-07Mar2011