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Hicum Model in Spectre

Hicum Model in Spectre. Diana Moncoqut, R&D manager June 4, 2004. CMI (Compiled Model Interface). A flexible and efficient low-level C-language interface A common model interface to Spectre,SpectreRF, AMS, UltraSim. Used to implement all kind of devices in the simulators:

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Hicum Model in Spectre

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  1. Hicum Model in Spectre Diana Moncoqut, R&D manager June 4, 2004

  2. CMI (Compiled Model Interface) • A flexible and efficient low-level C-language interface • A common model interface to Spectre,SpectreRF, AMS, UltraSim. • Used to implement all kind of devices in the simulators: Transistors: Bsim3v3, Bsim4, Hicum, Mextram, Vbic,.. Passive Devices: Resistor, Capacitor, Inductor, Core, Port.. • Used by customers to introduce their proprietary models to Spectre.

  3. Implementation in Spectre • First implementation was done by Conexant using CMI in 1999 • Minor enhancements made by Cadence • Update to version 2.1 in 2001 made by Cadence • Enhancements suggested by ST to the substrate current Itss: • Itss(T) = Itss(T0) * (T/T0)^(3/Msf) * exp(VGB/(Msf*Vt) * (T/T0-1))) • Tef0 constant change from 0.01 to 1e-6 Temperature Implementation is now complete in Spectre/RF

  4. Hicum model advantages A physically based-model • Hicum model is the only model that accurately describes the minority charge and transit time • Hicum model also gives a very accurate and robust large signal simulation

  5. Hicum model status in Spectre • Diffusion capacitances are a simplified representation of the distributed minority charge in the transistor • C_de/C_dc are not exact derivatives of Q_de/Q_dc • This causes convergence problems in transient analysis Provided a work-around for this problem, and working on a complete solution in Q3. Any remaining problems in derivatives will be examined and fixed in Q3.

  6. Hidden state problem in RF simulation • Hidden-state problem A hidden state is a variable whose value is used before it is set, which means that its value is retained from a previous time point. In shooting-Newton, one must be able to access and manipulate the state of the circuit, one must be able to compute the sensitivity of v(t) with respect to v(0) Hidden states are a problem for any RF simulator based on PSS algorithms.

  7. Hicum model status in Spectre • In Hicum, Excess phase (aQf, aiT) is implemented using a second-order Bessel polynomial which introduces hidden states. For PSS to converge, we must « expose » the states by explicitely adding new signals in the system. Excess Phase Problems are solved in Spectre/RF by exposing the hidden states • Exponential limiting. Dexp is used but EXP_MAX and EXP_MIN are not defined. Exponential limiting and PnJ limiting are added to Spectre/RF

  8. Status of Customer Pcrs on the Hicum model

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