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Unidirectional TVS models

Transient-voltage suppressor for one polarity Compare its models in the same order shown in the component inspector.

Symbol

Unidirectional TVS symbol
Default symbol for a new Unidirectional TVS component.

Model choice belongs to each placed Unidirectional TVS component. Changing one component does not change other instances or the default for future placements.

1

Standard

Forward conduction with fixed breakdown behavior set by the Zener voltage.

Default
Qualified analyses
  • Operating point
  • DC sweep
  • AC sweep
  • Transient

Model definition

The Standard model behaves as a conventional diode in the forward direction and enters reverse breakdown near the selected Zener voltage.

Its forward and breakdown coefficients are fixed rather than fitted from additional datasheet points.

Equations

Ij=2.5 nA ⁣[exp⁡ ⁣(Vj1.8VT)−1],VD=Vj+0.45 Ω IDI_j=2.5\,\mathrm{nA}\!\left[\exp\!\left(\frac{V_j}{1.8V_T}\right)-1\right],\qquad V_D=V_j+0.45\,\Omega\,I_D
The forward path is a fixed native diode curve with 0.45 Ω series resistance.
BV=VZ,IBV=1 mA,NBV=1.8BV=V_Z,\qquad I_{BV}=1\,\mathrm{mA},\qquad NBV=1.8
The selected Zener voltage becomes the native breakdown voltage; breakdown current and emission coefficient are fixed.
CJ=0,τT=0C_J=0,\qquad \tau_T=0
The model adds neither junction capacitance nor stored charge.

Parameters

ParameterDefaultAccepted values
Zener voltageReverse breakdown (Zener) voltage magnitude.5.1 VGreater than 0

Limits

  • The breakdown slope, leakage, and test-current behavior are fixed.
  • Temperature coefficient, noise, and junction capacitance are omitted.
2

Regulation

Breakdown voltage and dynamic resistance calibrated at a stated Zener current, with reverse leakage.

Qualified analyses
  • Operating point
  • DC sweep
  • AC sweep
  • Transient

Model definition

Regulation fits the reverse characteristic at a stated Zener current, adds the selected local dynamic resistance, and matches one leakage point below breakdown.

The forward direction remains diode-like, so the same Part can conduct normally if its polarity reverses.

Equations

RL=VRIR,IB=IZ−VZRLR_L=\frac{V_R}{I_R},\qquad I_B=I_Z-\frac{V_Z}{R_L}
The leakage point sets a parallel resistance. Iᴮ is the current that remains in the breakdown branch at the Zener test point.
RB=(1rZ−1RL)−1R_B=\left(\frac{1}{r_Z}-\frac{1}{R_L}\right)^{-1}
The native breakdown branch supplies the remaining incremental conductance after the leakage resistor.
RS=0.1 Ω,BV=VZ−IBRS,NBV=(RB−RS)IBVTR_S=0.1\,\Omega,\qquad BV=V_Z-I_B R_S,\qquad NBV=\frac{(R_B-R_S)I_B}{V_T}
These values calibrate the native diode's breakdown point and local slope exactly at (VZ, IZ).
Ij=10−14 ⁣[exp⁡ ⁣(VjVT)−1],VD=Vj+RSIDI_j=10^{-14}\!\left[\exp\!\left(\frac{V_j}{V_T}\right)-1\right],\qquad V_D=V_j+R_S I_D
The forward path uses a unit-emission diode with the same fixed series resistance.
VZ(I)≈VZ+rZ(I−IZ)V_Z(I)\approx V_Z+r_Z(I-I_Z)
The resulting terminal curve has the selected local dynamic resistance at the reference current.

Parameters

ParameterDefaultAccepted values
Zener voltageReverse voltage at the stated Zener test current.5.1 V; at IZT 5 mAGreater than 0; reference condition greater than 0
Dynamic resistanceSmall-signal Zener impedance at the stated Zener test current.10 ΩGreater than 0
Reverse leakageReverse leakage current below breakdown at the stated reverse voltage.1 µA; at VR 3 VGreater than 0; reference condition greater than 0

Limits

  • The fit is local to one test-current point.
  • Breakdown-knee detail, temperature drift, noise, and capacitance are omitted.
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