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  1. #41
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    Re: Design of the startup switch

    Quote Originally Posted by tisheebird View Post
    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)
    You can use the configuration of my post #38. Just replace the Vcp voltage source by a 3.6V source.

    Quote Originally Posted by tisheebird View Post
    Every circuit has it's own complementary circuit. If post #25 is possible then it's complementary is also possible..right..?
    Of course it's possible, but I think this won't solve your problem. Just try it!



    •   Alt23rd February 2018, 21:09

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  2. #42
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    Re: Design of the startup switch

    Quote Originally Posted by erikl View Post
    You can use the configuration of my post #38. Just replace the Vcp voltage source by a 3.6V source.



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


    can you send me the schematic again...?



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    Re: Design of the startup switch

    Quote Originally Posted by tisheebird View Post
    can you send me the schematic again...?
    Why? It's still available!



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    Re: Design of the startup switch

    Quote Originally Posted by erikl View Post
    Why? It's still available!

    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..?



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    Re: Design of the startup switch

    Quote Originally Posted by tisheebird View Post
    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..?
    You could easily reduce the number of stages yourself. I'm not your babysitter.



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    Re: Design of the startup switch

    Quote Originally Posted by erikl View Post
    You could easily reduce the number of stages yourself. I'm not your babysitter.

    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..Click image for larger version. 

Name:	equ._circuit.png 
Views:	6 
Size:	7.1 KB 
ID:	144993



  7. #47
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    Re: Design of the startup switch

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

    Where do you see latchup?



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    Re: Design of the startup switch

    Quote Originally Posted by erikl View Post
    Show your switch in its current state, including W & L values!

    Where do you see latchup?
    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...



    •   Alt28th February 2018, 16:30

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  9. #49
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    Re: Design of the startup switch

    Quote Originally Posted by tisheebird View Post
    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.
    So this is the output impedance of your charge pump?!

    Quote Originally Posted by tisheebird View Post
    This is basically the substrate resistance and it should be very very small to avoid latch-up.
    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.



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    Re: Design of the startup switch

    Quote Originally Posted by erikl View Post
    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.

    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 - - -

    Quote Originally Posted by erikl View Post
    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.
    Could you tell me how to proceed...



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    Re: Design of the startup switch

    Quote Originally Posted by erikl View Post
    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.


    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 - - -

    Quote Originally Posted by erikl View Post
    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.

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



  12. #52
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    Re: Design of the startup switch

    Quote Originally Posted by tisheebird View Post
    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.
    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!


    Quote Originally Posted by tisheebird View Post
    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..??
    Rout=400kΩ seems quite normal at a load current of 1A (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.



    •   Alt28th February 2018, 21:45

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  13. #53
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    Re: Design of the startup switch

    Quote Originally Posted by erikl View Post
    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 1A (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.

    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 (400KClick image for larger version. 

Name:	pic (2).png 
Views:	4 
Size:	92.6 KB 
ID:	145006)..

    - - - Updated - - -

    Quote Originally Posted by erikl View Post
    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 1A (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.

    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.



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    Re: Design of the startup switch

    Quote Originally Posted by tisheebird View Post
    Could you tell me how did you calculate 400mV loss...??
    Have you ever heard of Ohm's Law? Then use it!



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    Re: Design of the startup switch

    Quote Originally Posted by erikl View Post
    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 1A (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.


    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....



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    Re: Design of the startup switch

    Quote Originally Posted by tisheebird View Post
    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....
    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...



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    Re: Design of the startup switch

    Quote Originally Posted by erikl View Post
    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 1A (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.

    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 - - -

    Quote Originally Posted by erikl View Post
    Have you ever heard of Ohm's Law? Then use it!

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



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