Stability analysis

011_rttemp_thermal_RC : Stability analysis

Requires: SmartSpice & Smartview

Minimum Versions: SMARTSPICE 3.17.26.C

The thermal equation extension for .RTTEMP is intended to adjust a chip temperature (Tj) during transient analysis and calculating the devices contribution to the total chip power dissipation (Pd). For full decription, read SmartSpice User's manual vol.1 pages 2-247- 2-249.

This input deck shows how to use .RTTEMP thermal extension to calculate and update chip temparature adjusted to the chip power dissipation. The User should specify duration TD, overlap time TO, ambient temperature TA, thermal resistance TR and runtime expression fm[I(devicem),V(nodes)] for all necessary devices.

Statement:

.rttemp thermal TA=27 TR=50 TD=150u TO=50u + ' I(R1)*(V(1)-V(2)) + I(R2)*I(R2)*2e3 + I(C1)*V(2) '

In this case, SMARTSPICE will save the calculated temperatures Tj1 in vector 'temp'. For example, at point tj1=150u the terms I(R1)*V(1,2), I(R2)*I(R2)*2e3 and I(C1)*V(2)are calculated and summed according equation (2) from the SmartSpice User's manual vol.1 page 2-247, Tj1 is calculated according (1) and circuit temperature is updated to Tj1. After that simulation continues to the timepoint tj2=250u where steps are repeated and circuit temperature is updated to Tj2.

Output: This statement will save calculated temperatures Tj in the vector 'temp' during the transient analysis. For this example, figure 2-9 Vectors ("temp" and "currenttemp") is shown on page 2-249 SmartSpice User's manual vol.1.