VBIC Version 1.2 Released in SmartSpice and
UTMOST III

Introduction

The latest VBIC bipolar model v1.2 of Sep 24 1999 has been integrated into SmartSpice and UTMOST III. It can be invoked by specifying the model selector LEVEL=5 and the version selector VERSION=1.2. in the .MODEL card. This new version becomes the default VBIC model.

A new model parameter REVISION has been introduced to invoke future updates or older VBIC models. In SmartSpice/UTMOST III, only the old version 1.1.5 is still supported and can be invoked by specifying VERSION=1.1 and REVISION=5. If other values are given, v1.2 is assumed. Aliases are listed in Table 1.


VERSION (VERS) Description Units Default
VERSION (VERS) Version parameter. Only 1.1 (if REV=5) and 1.2 (if REV= 0) are permitted, otherwise 1.2 is assumed.
--
1.2
REVISION (REV, VREV) Revision parameter. Only 0 (if VERS=1.2) and 5 (if VERS=1.1) are permitted, otherwise 0 is assumed.
--
0

Table 1.


The explicit specification of VERSION and REVISION is strongly recommended to avoid incompatibility problems between v1.1.5 and v1.2.

 


New Features in VBIC v1.2


Here is a summary list of major updates and enhancements announced in v1.2 and relative to v1.1.5:

  • temperature dependence of IKF

  • separate temperature coefficients for intrinsic and extrinsic resistances RCX, RBX and RBP

  • simple exponential base-emitter breakdown model

  • reach-through model to limit base-collector depletion capacitances

  • separate activation energy for ISP

  • selector available to switch to SGP qb formulation

  • high-current roll-off coefficient

  • fixed collector-substrate capacitance

  • separate IS allowed for reverse operation in HBTs

  • error fixed in the built-in potential temperature mapping (psibi function)


All these new features have been implemented in SmartSpice. Only the 3-terminal version of the model described in the official release is not currently supported. Due to some of these changes, VBICv1.2 is not fully backward compatible WIDTH the previous version (1.1.5).

 

New Model Parameters in VBICv1.2


All parameters supported in v1.1.5 are still used in v1.2. However, the definition has slightly changed for the following ones:

Due to the separation of the temperature dependence for intrinsic and extrinsic resistances, XRC and XRB now correspond to XRCI and XRBI, respectively. Aliases XRCI and XRBI have been added for convenience. Due to changes in the formulation of the single piece depletion capacitance model, the smoothing factors AJE, AJC, AJS are now expressed in volts.

VBICv1.2 has 19 new model parameters that are shown in Table 2.

Parameter (alias) Description Units Default
XRBX Temperature exponent of extrinsic resistance RBX
-
0.0
XRCX Temperature exponent of extrinsic resistance RCX
-
0.0
XRBP Temperature exponent of extrinsic resistance RBP
-
0.0
XIKF Temperature exponent of IKF
-
0.0
ISRR Reverse saturation current factor (HBTs)
-
1.0
XISR Temperature exponent of ISRR (HBTs)
-
0.0
DEAR Activation energy shift for ISRR (HBTs)
V
0.0
EAP Activation energy for ISP
V
1.12
VBBE Base-Emitter breakdown voltage, zero means infinity
V
0.0
TVBBE1 First temperature coefficient of VBBE  
0.0
TVBBE2 Second temperature coefficient of VBBE  
0.0
NBBE Base-Emitter breakdown emission coefficient
-
1.0
TNBBE Temperature coefficient of NBBE  
0.0
IBBE Base-Emitter breakdown current
A
1.0e-6
QBM Selector for SGP qb formulation
A
0.0
NKF High current roll-off coefficient
-
0.5
VRT B-C reach-through limiting voltage (0 means infinity)
V
0.0
ART B-C reach-through limiting smoothing factor
V
0.1
CCSO Fixed collector-substrate capacitance
F
0.0

Table 2.

New Temperature Mappings


The following abbreviations are defined for convenience:

where TNOM is the temperature at which model parameter extraction has been done. Td corre-sponds to the dynamic temperature if self-heating is turned on or to the operating temperature otherwise.


  • A bug in psibi mapping with temperature has been fixed. The psibi function is used to calculate built-in potentials PE, PC and PS at the device temperature as a function of related model parameters and activation energies EAIE, EAIC and EAIS, respectively. The updated expressions are (actually, only the expression pssio has been corrected):




  • Some equations have been updated according to new model parameters:




  • New equations have been added:




New Current Equations
  • The equation of the ideal reverse current has been modified to account for a separate saturation current IS in reverse operation (HBTs). However backward compatibility is maintained if new model parameters ISSR, XISR and DEAR are unspecified (default values lead to). The new equation is:




  • Two expressions for the base charge equation are now available and can be selected using the model parameter QBM. The standard Gummel-Poon formulation has been introduced. The high-current roll-off coefficient NKF is also supported. If NKF is unspecified, its default value is equal to 0.5 and the first expression reduces to for back-ward compatibility with v1.1.5.




  • If VBBE > 0.0, a new contribution is added to intrinsic and extrinsic base-emitter currents Ibe and Ibex to account for the B-E breakdown effect:




New Charge Equations
  • A new depletion capacitance model with optional reach-through limiting has been introduced to evaluate normalized depletion charges qdbc and qdbep (other depletion charges are still evaluated using the function qj). Assuming that V is the junction applied voltage, P is the junction built-in potential, FC is the forward bias depletion capacitance limit, M is the junc-tion grading coefficient and AJ is the smoothing factor, the new function qjrt is defined by:




It is important to notice that qj and qjrt functions are identical if VRT is set to zero (no reach- through limiting). The influence of the reach-through limiting on normalized depletion capacitances only occurs for reverse biased junction as shown on Figure 1 and Figure 2. Figure 1 corresponds to the SGP-like model, where the depletion capacitance linearly increases for values of forward bias greater than FC.P. Figure 2 corresponds to the single piece model where the depletion capacitance smootly limits to its value at FC.P. The effect of reach-through limiting is similar for both models.

Figure 1. Figure 2.


Another important point is that the qj function implemented in v1.1.5 has been slightly modified in v1.2. The smoothing factor AJ has been replaced by 4*AJ*AJ in vl and vl0 expressions.
  • The contribution of the fixed capacitance CCSO has been added to the base-collector charge Qbcp of the parasitic device. The new equation is: