Time step error at "VDS1" when I want to do transient simulation

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Time step error at "VDS1" when I want to do transient simulation

722 Views
MohMor
Contributor III

Hello,

I am using AFIC10275's large-signal model. when I connect all the stuffs to IC and then, do transient simulation in ADS, I face an Time step error after 120 ps. After analyzing my circuit, I realized that the problem occurs at node VDS1. IC do not have any problem when I do the simulation without any connection to other stuffs. Also, I have connected DC voltage to the VDS1 with and without a couple of small and large capacitor in parallel, large inductor in series, and small resistor in series. I set the function "PWL" as input to VDS1 in order to produce a ramp function. But it did not work.

Also, Time step error occurs when I set the VDS1 voltage at 50 volts, I mean, I do not have any problem if I set this voltage at 5 volts and lower.

May I know what is the solution if you know?

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4 Replies

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ErikaC
NXP TechSupport
NXP TechSupport

Hello, 

Thank you for the information.

These warns for all NXP (former Freescale) RF ADS product models. This warning occurs because we use generic inductors inside all SPDK's for mutual inductance. The warn is due to the negative value of the mutual inductance coupling the gate and drain inside the FET2 transistor. The negative value results from the direction of the 2 inductors being coupled. The value of inductors are ~0pH and doesn't influence the simulation.

This warning is not a concern. Since it is just a warning it can be reviewed and in this case ignored.

Regarding the error, I haven't seen this error before but I have found this solution in another forum:

"Sometimes, when ADS is performing an instantaneous simulation, the simulator will report an error, this situation usually means that during the simulation process of one or more nodes in the circuit structure, the frequency of signal changes exceeds the minimum time set by the simulator.

Solution: You can try reduce the emulator step."

Hope it helps.

Regards.

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681 Views
MohMor
Contributor III

Regarding the error, I haven't seen this error before but I have found this solution in another forum:

"Sometimes, when ADS is performing an instantaneous simulation, the simulator will report an error, this situation usually means that during the simulation process of one or more nodes in the circuit structure, the frequency of signal changes exceeds the minimum time set by the simulator.

Solution: You can try reduce the emulator step."

That is a general approach. I have performed a lot of other methods along with the method you mentioned above (as I said in the question text). It is enough to search for it on the web. You can find some of them in the following link:

(2) ADS error message:The internal timestep is too smaller. Help | Forum for Electronics (edaboard.c...

Even after decreasing the time step to 0.01ps (for a circuit with just DC supply) , the error exists yet and for 200ps simulation time, it gives error after finishing 76% simulation time. It is a simple circuit and I have uploaded the schematic, so you can do simulation yourself and reach to the same result. Please do that. 

if you can do transient simulation by just reducing time step, please place the time step and simulation time here. thank you.

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714 Views
ErikaC
NXP TechSupport
NXP TechSupport

Hello,

Are you using one of our reference designs? if so, which one? what frequency?

Can you copy and paste the error you receive, please?

Regards.

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711 Views
MohMor
Contributor III

Hello,

At first, I used the reference circuit below, which is available in AFIC10275's datasheet:

https://drive.google.com/file/d/1sJAC1XrGikzR9BSYHwp2V7DQEG_3CZxc/view?usp=sharing 

I have used the co-simulated PCB with RF signal at 1090 MHz frequency. Even without RF input, this error will be shown. But I get the time step error (I put the error message at the end of the message). Nonetheless, I assumed the error is with my generated PCB. So, I decided to check all the circuit node in the way that I connect circuit of just one node. When I connect VDS1 circuit (and all the node connection were disconnected), I faced with the same error shown here:

https://drive.google.com/file/d/1BOTCpqcF10F3YEdClqE-36QcTuOfvEyG/view?usp=sharing 

For more information, you can also refer to this link:

Time step error due to connection between DC supply and IC large-signal model - ADS | Forum for Elec...

I have uploaded my schematic here.

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