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Design of the startup switch

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tisheebird said:
Okay let's not talk about -6V now...
The Picture in post #25 is for -3.6V. I need similar structure which works as listed before (pulse=0V then output 0V and when it is 1.8V then -3.6V)...

Even when it is 1.8V then -3.3V is acceptable...but at input 0V it should be 0V bottom (output)
Click to expand...

You can use the configuration of my post #38. Just replace the Vcp voltage source by a 3.6V source.

tisheebird said:
Every circuit has it's own complementary circuit. If post #25 is possible then it's complementary is also possible..right..?
Click to expand...

Of course it's possible, but I think this won't solve your problem. Just try it!
 

tisheebird said:
Yes but for -3.6V why so many stacked transistors....it has to to be 2 stages max..So please could you give me for -3.6V..?
Click to expand...

You could easily reduce the number of stages yourself. I'm not your babysitter. :roll:
 

erikl said:
You could easily reduce the number of stages yourself. I'm not your babysitter. :roll:
Click to expand...


Thanks a lot....Actually i got my mistake and now it's okay...
Basically I need a switch which will reduce the output resistance (to 2-10 ohms) of my voltage generation circuit such that I won't have the latch up problem.
The equivalent circuit looks like the picture shown below. With a very low current...say 1uA, the resistance is nearly 400K. I need to reduce the resistance..I have to design a switch which will decrease the resistance value to very small. (2-10 ohms)

Thanks.. equ._circuit.png
 

Show your switch in its current state, including W & L values!

Where do you see latchup?
 

erikl said:
Show your switch in its current state, including W & L values!

Where do you see latchup?
Click to expand...

I am not using any switch or other circuitry to reduce the resistance value. But the value of Rs =400k now. I need some type to circuitry which will reduce the value to 2-10 ohms. This is basically the substrate resistance and it should be very very small to avoid latch-up.

So could you help me in this case...
 

tisheebird said:
I am not using any switch or other circuitry to reduce the resistance value. But the value of Rs =400k now. I need some type to circuitry which will reduce the value to 2-10 ohms.
Click to expand...
So this is the output impedance of your charge pump?!

tisheebird said:
This is basically the substrate resistance and it should be very very small to avoid latch-up.
Click to expand...
If you think so: you can't change the substrate resistance of a certain process. If you need a lower substrate resistance, choose a process which uses EPI wafers. Or an SOI process.
 

erikl said:
So this is the output impedance of your charge pump?!


If you think so: you can't change the substrate resistance of a certain process. If you need a lower substrate resistance, choose a process which uses EPI wafers. Or an SOI process.
Click to expand...


Yes this is my output impedance of the charge pump circuit at very low current (1uA). I am also using EPI wafers CMOS 180 nm technology.

- - - Updated - - -

erikl said:
So this is the output impedance of your charge pump?!


If you think so: you can't change the substrate resistance of a certain process. If you need a lower substrate resistance, choose a process which uses EPI wafers. Or an SOI process.
Click to expand...

Could you tell me how to proceed...
 

erikl said:
So this is the output impedance of your charge pump?!


If you think so: you can't change the substrate resistance of a certain process. If you need a lower substrate resistance, choose a process which uses EPI wafers. Or an SOI process.
Click to expand...



I would like to update you that Rs=400K is the output resistance of the charge pump circuit and Vout=-6V is given to the P-well in the CMOS 180nm technology. I want to reduce this resistance value to few tens of ohms..Could you suggest me anything..??

- - - Updated - - -

erikl said:
So this is the output impedance of your charge pump?!


If you think so: you can't change the substrate resistance of a certain process. If you need a lower substrate resistance, choose a process which uses EPI wafers. Or an SOI process.
Click to expand...


To avoid confusion let's call it as Rout= 400K....
 

tisheebird said:
I would like to update you that Rs=400K is the output resistance of the charge pump circuit and Vout=-6V is given to the P-well in the CMOS 180nm technology.
Click to expand...

Where is your P-well? In an N-well of a p-substrate or directly in an n-substrate? Show your process details (doping of well(s) and EPI layer) if you want help!


tisheebird said:
To avoid confusion let's call it as Rout= 400K....
I want to reduce this resistance value to few tens of ohms..Could you suggest me anything..??
Click to expand...

Rout=400kΩ seems quite normal at a load current of 1µA (you loose just 400mV). I don't think you can do better, even with a different charge pump.

No, I can't suggest a better solution, sorry.
 

erikl said:
Where is your P-well? In an N-well of a p-substrate or directly in an n-substrate? Show your process details (doping of well(s) and EPI layer) if you want help!




Rout=400kΩ seems quite normal at a load current of 1µA (you loose just 400mV). I don't think you can do better, even with a different charge pump.

No, I can't suggest a better solution, sorry.
Click to expand...


I have attached the picture...

Could you tell me how did you calculate 400mV loss...??...I have read that the resistance should be as low as possible because latch-up is possible at this value (400Kpic (2).png)..

- - - Updated - - -

erikl said:
Where is your P-well? In an N-well of a p-substrate or directly in an n-substrate? Show your process details (doping of well(s) and EPI layer) if you want help!




Rout=400kΩ seems quite normal at a load current of 1µA (you loose just 400mV). I don't think you can do better, even with a different charge pump.

No, I can't suggest a better solution, sorry.
Click to expand...


If Rout= 400K, then don't you think it is prone to latch-up problem..?? I saw in docs that the output resistance is ~50 ohms...
I don't want to face latch-up problem.
 

erikl said:
Where is your P-well? In an N-well of a p-substrate or directly in an n-substrate? Show your process details (doping of well(s) and EPI layer) if you want help!




Rout=400kΩ seems quite normal at a load current of 1µA (you loose just 400mV). I don't think you can do better, even with a different charge pump.

No, I can't suggest a better solution, sorry.
Click to expand...



Thanks a lot...I would like to update you that when the supply VDD=0V then the output resistance of my charge pump is ~400K. But when the supply is 1.8V then the output impedance is ~8K at 1uA of load current...The worrying problem is during the start-up condition...I think this won'y work in the real time due to latch-up problem...What do you say on that..??

- - - Updated - - -

The idea is to have very low resistance when the supply is 0V....
 

tisheebird said:
Thanks a lot...I would like to update you that when the supply VDD=0V then the output resistance of my charge pump is ~400K. But when the supply is 1.8V then the output impedance is ~8K at 1uA of load current...The worrying problem is during the start-up condition...I think this won'y work in the real time due to latch-up problem...What do you say on that..??

- - - Updated - - -

The idea is to have very low resistance when the supply is 0V....
Click to expand...

We need a switch whose resistance is very low (5-10 ohms) such that connected to the output node..Could you please guide me with some suggestions...
 

erikl said:
Where is your P-well? In an N-well of a p-substrate or directly in an n-substrate? Show your process details (doping of well(s) and EPI layer) if you want help!




Rout=400kΩ seems quite normal at a load current of 1µA (you loose just 400mV). I don't think you can do better, even with a different charge pump.

No, I can't suggest a better solution, sorry.
Click to expand...


Guide me with some circuitry whose resistance is few ohms such that I can connect to my charge pump circuit to avoid latch up problem...Please..

- - - Updated - - -

erikl said:
Have you ever heard of Ohm's Law? Then use it!
Click to expand...


I am unable to proceed...Please guide me with some circuitry...
 

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