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[Help-gnucap] Re: NTC and PTC

From: nbs
Subject: [Help-gnucap] Re: NTC and PTC
Date: Thu, 08 Jun 2006 21:27:11 +0900
User-agent: Thunderbird 1.5 (X11/20060317)

Hello Markus,

There are two ways for simulating thermal effects:

1. Native (and somewhat limited) Spice method. Use a resistor model and
define tc1, tc2 parameters.

That might be something like this (not checked):

.model NTCRES R res=1k tc1=-1 tc2=0.01
Rntc1 n1 n2 NTCRES
Rntc2 n3 n4 NTCRES temp='temp_param'

Temperature of Rntc1 is set in simulation options. Temperature of Rntc2
is equal to the 'temp_param' parameter value.

Refer to this page for details:
(BTW. in the description of tc1, tc2 should be [Ohm/degree C], I guess)

2. Above method cannot be used for simulating dynamic thermal effects
(this is a limitation of Spice) as temperature is constant within a
simulation sweep. You may want to design your own resistor model where
temperature will be represented as a signal (for example a node voltage).

Here is an example of what could be possibly used in hspice:

i_ntc1 n1 n2 cur='v(n1,n2)/(resistance_value+tc1_param*v(temp_val)'
v_temperature temp_val 0 pwl (0 0, 1s 10, 3s -10, 4s 0)


> Hi,
> I founded the fit command.
> Ihis possible, that i can use the fit command to get an NTC or PTC?
> For example,
> R1 2 0 fit 2k,22°C 1k,30°C 500,40°c 250,50°c order=1
> Maybe the Temperatur will not be increased, and therefore the Value of
> the Resistor will not be sweeped?
> Are there any Ideas?
> mfg Markus

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