  Forum Pages: 1 high frequency source VS. long rise time(parallel RC) in transient simulation (Read 1041 times)
 Peng_Li Junior Member  Offline Posts: 10 Hangzhou, China high frequency source VS. long rise time(parallel RC) in transient simulation Aug 24th, 2018, 5:24am   Hi, the title is a brief description of the problem. Here are the details. For simplicity, my circuit is composed of two parts, part 1 is a PULSE current souce in series with a resistor and a inductor, described in Verilog-A.Part 2 is a parallel RC circuit, excited by another current source whose magintude is the dissipated power of part one, described in Verilog-A or SPICE.There are connections between the two circuits.Firstly, the dissipated power of part 1 is delivered to part 2 by a VCCS (voltage-controlled current source) module.Secondly, the values of resistor and inductor in part 1 circuit varies with the node voltage VT1 in part 2 cirucit.My problem is that, the PULSE current souce in part 1 circuit varies at high frequency (the period can be several nanoseconds), however, it takes a long time for the RC in part 2 circuit to rise up (the time can be several seconds). (specific values of RC is shown in the following code)Actually, I tried to change the PULSE souce into a step source, to avoid this problem, and it worked (as shown in the following code). But I want to solve this problem eventually.Is there any way to solve this problem? Maybe, delay the variation in part 1, using a counter within a if...else... block in verilog-A module of part 2 circuit?Any help would be greatly appreciated.Sincerely.The code for each module is shown as follows.step current source in HSPICE Code:```.param v01=0 va1=1.9610e-03 td11=10 tau11=2.275 td21=500 tau21=20000 Istep10 0 nstep1 exp(v01 va1 td11 tau11 td21 tau21) Xtop1 nstep1 0 npwr10 dt10 top_level .TRAN 0.001 150 ```PWL current source Code:```Ipul1 0 n1 PULSE 0.000000e+00 1.961000e-03 0.000000e+00 8.570000e-10 8.570000e-10 2.713000e-09 7.140000e-09 ```Top level module Code:```module top_level (n1,n2,npwr,dt); � � inout n1,n2,npwr,dt; electrical n1,n2,npwr,dt; ground gnd; parameter real r = 0.0244; parameter real l = 1.3215e-12; parameter real rth = 3.0556e+08 from [0:inf); parameter real cth = 3.0191e-08 from [0:inf); //source input from Hspice //instantiate 3 modules series_rl_power_rl_varywith_temp #(.r_ini(r), .l_ini(l)) series_rl_varypower(n1,n2,npwr,dt); �//Part 1 circuit vccs #(.gain(1.0)) vccs_4therm (gnd,dt,npwr,gnd); thermalpallrc #(.r(rth), .c(cth)) thermal_rc(dt,gnd); �//Part 2 circuit endmodule ```Part 1 circuit Code:```module series_rl_power_rl_varywith_temp (p, n, pwr, tin); //Does this model work well for both v-source and I-source? to be tested � � parameter real r_ini = 0.0244; // resistance (Ohms) � �parameter real l_ini = 1.3215e-12; // inductance (H) parameter real p1 = 8.912e-05, p2 = 0.02432; //fitted parameters for R_metal parameter real a = 1.338e-12, b = 1.534e-05, c = -1.699e-14, d = -0.01113; inout p, n; input tin; output pwr; � �electrical p, n, pwr, tin; ground gnd; � �analog begin V(p,n) <+ (p1*V(tin,gnd) + p2)*I(p,n) + (a*exp(b*V(tin,gnd)) + c*exp(d*V(tin,gnd)))*ddt(I(p,n)); V(pwr,gnd) <+ V(p,n)*I(p,n); � �end endmodule ```Part 2 circuit Code:```module thermalpallrc (p, n); � �parameter real r=3.0556e+08 exclude 0; � �parameter real c=3.0191e-08; � �inout p, n; � �electrical p, n; � �analog begin I(p,n) <+ V(p,n)/r + ddt(c*V(p,n)); � �end endmodule ```VCCS Code:```module vccs (p, n, ps, ns); � �parameter real gain=1.0; � �output p, n; � �input ps, ns; � �electrical p, n, ps, ns; � �analog begin I(p,n) <+ gain*V(ps,ns); � �end endmodule ``` Back to top IP Logged
 Peng_Li Junior Member  Offline Posts: 10 Hangzhou, China Re: high frequency source VS. long rise time(parallel RC) in transient simulation Reply #1 - Aug 24th, 2018, 6:52am   Diagram of the circuits are shown here. [img][/img] Back to top  IP Logged
 Ken Kundert Global Moderator     Online Posts: 2277 Silicon Valley Re: high frequency source VS. long rise time(parallel RC) in transient simulation Reply #2 - Aug 24th, 2018, 9:29am   Use PSS analysis to directly find the steady-state behavior.-Ken Back to top IP Logged
 Peng_Li Junior Member  Offline Posts: 10 Hangzhou, China Re: high frequency source VS. long rise time(parallel RC) in transient simulation Reply #3 - Aug 26th, 2018, 7:45pm   Ken Kundert wrote on Aug 24th, 2018, 9:29am:Use PSS analysis to directly find the steady-state behavior. Thanks. I didn't use PSS before. From Google results, it seems that the PSS analysis is mostly used in Cadence, and applied to oscillator in RF analysis.Since I need to calculate the power of Part 1 circuit, and delivery the value of power to Part 2 circuit, I am not sure whether this can be done in Candence. Back to top IP Logged Pages: 1