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Adding a pulsed switch to a dc voltage source in cadence library

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iaf

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i want to add a switch for creating a pulsed output with a certain frequency. I know that the voltage source could be pulsed but i need to keep it on a certain dc voltage and the switch will just have to follow this voltage. does anyone have an idea which component in cadence lib would achieve that? Thanks
 

H,

this is about no usable information.

Try to give values with units. At least a range from min to max...
and/or (hand drawn) circuits, waveforms with units, flow charts...

Please understand that informations like "certain frequency", "voltage source could be pulsed", "certain DC level" ... are abslolutely useless

Klaus
 

i just need to simulate a 50MHz pulse by using a 3.3V DC voltage source, and i want to use a switch for that because the dc voltage is changing and i want the clock to follow the max voltage of the circuit
 

You can either use a CMOS inverter supplied by the varying voltage or a SPDT switch (complementary switching SW components).
 

is there such a switch in cadence? i don't want to use MOSFETs as they are temperature dependant i would prefer using an ideal switch in that case
 

is there such a switch in cadence?
Cadence is a tool vendor, the simulator is Spectre. There is an ideal switch SW in SPICE and Spectre And there is a manual named Spectre Circuit Simulator Reference. Another option is a behavioral voltage source (B component).
 

i have in cadence a library called cadencelib which i'm using for simulating ideal components i guess it comes with cadence and that's the one i wanted to use
 

It seems you try to do simple thing in very complicated way.
Describe once again what you would like to achieve. It can be graphical explanation too.
 

You could consider using poly sources (vcvs) to create Vdd and the "switching input", a (say) 0-1V ramp at one terminal pair for the time varying aspect, a V=3.3 source multipled by the ramp is your rising Vdd and do the same scaling for a 0-Vdd pulse source through a second poly vcvs.

Or you could go grab yourself a veriloga (or transistor level) inverter cell and string a couple together, powered off Vdd and passing the logic signal.
 

i just need to simulate a clock signal out of my Vdd which is a DC voltage(which could vary). I was simulating with a pulsed voltage source but i want to make it more realistic as it's not possible to have the clock amplitude differing from my vdd

- - - Updated - - -

You could consider using poly sources (vcvs) to create Vdd and the "switching input", a (say) 0-1V ramp at one terminal pair for the time varying aspect, a V=3.3 source multipled by the ramp is your rising Vdd and do the same scaling for a 0-Vdd pulse source through a second poly vcvs.

Or you could go grab yourself a veriloga (or transistor level) inverter cell and string a couple together, powered off Vdd and passing the logic signal.

i'm trying to find something ideal because i don't want all the parasitic effects to be shown. I didn't get the poly source concept, could you explain it more?
 

does anyone have an idea which component in cadence lib would achieve that?
i have in cadence a library called cadencelib which i'm using for simulating ideal components
What do you want to mean by”Cadence lib” ?
As far as I know, such library does not exist anywhere.
Use correct terminology.

Create custom signal source by Verilog-A.
 

cadence_lib.PNG
That's the library i'm using
 

That's the library i'm using
You can not understand tools which you use at all.

They are just symbol’s library which are supplied with Cadence dfII.

You can see available all Spectre primitives by “spectre -h”.
Some of Spectre primitives are reflected as symbol in “analogLib” and “rfTlineLib”.

You can see Verilog-A models in “ahdlLib”, “bmslib”, “rfLib”, “pllLib” and “pllMMLib”.
However these are not useful for specific application.

Create custom signal source by Verilog-A.
 
Last edited:

You can not understand tools which you use at all.

They are just symbol’s library which are supplied with Cadence dfII.

You can see available all Spectre primitives by “spectre -h”.
Some of Spectre primitives are reflected as symbol in “analogLib” and “rfTlineLib”.

You can see Verilog-A models in “ahdlLib”, “bmslib”, “rfLib”, “pllLib” and “pllMMLib”.
However these are not useful for specific application.

Create custom signal source by Verilog-A.

I'm not familiar with these expressions and don't know how to create something by verilog -A. Isn't there any ready component that could do this simple functionality?
 

The author is so unclear...
What I have understood, the point here is to have square wave with 50MHz frequency, and levels between ground and vdd, while vdd is defined by another vdc source. This vdd is a variable. If so, use the same variable in vpulse component as second voltage.
If my understanding is incorrect, please explain your issue clearly.

BTW. VerilogA module or any more complicated stuff is not needed IMO
 

Ideal switch and behavioral voltage source have been previously suggested as possible solution. I'm sure they are somehow available in your schematic libraries. I don't use the tool, thus I can't help in this regard.
 

The author is so unclear...
What I have understood, the point here is to have square wave with 50MHz frequency, and levels between ground and vdd, while vdd is defined by another vdc source. This vdd is a variable. If so, use the same variable in vpulse component as second voltage.
If my understanding is incorrect, please explain your issue clearly.

BTW. VerilogA module or any more complicated stuff is not needed IMO

that couldn't be achieved as setting the amplitude in a pulsed source couldn't be changed in a transient simulation, the same applies for the ideal switch it can't be switched in transient response
 

the same applies for the ideal switch it can't be switched in transient response
No. Ideal switch means SPICE SW component is controlled by a pulsed voltage source, it's only use is in transient simulation.

Similarly you can use behavioral voltage source, e.g. output voltage = product of voltage a and voltage b
 

No. Ideal switch means SPICE SW component is controlled by a pulsed voltage source, it's only use is in transient simulation.

Similarly you can use behavioral voltage source, e.g. output voltage = product of voltage a and voltage b

ok i have found this switch, i guess the vn and vp are the 2 nodes of the switch. are the vctrln/p the voltage sources i have to feed to control the switching of it? like how should i connect these 2 other nodes?
 

I have simulated the switch with the following parameters but it's still giving the input signal

switch.PNG

switch_02.PNG

switch_3.PNG

switch_4.PNG

switch_5.PNG
 

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