1. 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

2. SPICE Diode Temp. Eqs.1
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3. Corrections in some versions of SPICE
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4. SPICE Diode Temp. Pars.1 PARAMETER definition and units default value
XTI IS temperature exponent 3.0
TIKF ikf temperature coefficient (linear) °C
TRS1 rs temperature coefficient (linear) °C
TRS2 rs temperature coefficient (quadratic) °C
TBV1 bv temperature coefficient (linear) °C
TBV2 bv temperature coefficient (quadratic) °C
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
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5. Thermal Resistance
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6. 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
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7. 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.
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8. 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
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9. PiN Diode Depletion Fields
Normalized Position, x’ = x/Wi
Normalized Field, E/Em,P-T
dx’p
dx’n
x’n
-x’p
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10. PiN Diode Depletion Conditions
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11. CV data and N(x) calculation
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12. 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
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13. Diode switching (cont.)
VF,VR >> Va
F: t < 0 Sw RF
R: t > 0 VF + RR D VR +
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14. Diode charge for t < 0 pn
pno x xn
xnc
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15. Diode charge for t >>> 0 (long times)pn
pno x xn
xnc
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16. Equation summary
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17. Snapshot for t barely > 0pn
Total charge removed, Qdis=IRt
pno x xn
xnc
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18. I(t) for diode switchingID IF ts
ts+trr t
- 0.1 IR
-IR
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19. 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.
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