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    Capacitive Boost or Charge-Pump DC-DC Converter

    hello, i would require some advice on the capacitive DC-DC Converter that can generate several selectable DC voltage sources from a single given DC voltage source. The generated DC output voltages are multiple times of the input DC level when unloaded. It uses the concept of the Dickson charge pump, by multiple flipping of the charged capacitor onto another capacitor. The power transistors, controller and the capacitors are meant to be integrated together. The output should be able to efficiently deliver acceptable amount of power in tens to hundreds of mW.

    I am using 0.18um Cmos technology simulated in Cadence-virtuoso and would like to seek some advice because i'm new to the IC-design industry. I hope to seek your understanding to guide me through this project.

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    Re: Capacitive Boost or Charge-Pump DC-DC Converter

    Diagrams of the Dickson frequently have two clocks driving it. These are in fact a full H-bridge which turns the DC supply into AC applied to the network. The circuit becomes similar to a half-wave parallel multiplier.

    Each capacitor charges to a greater level than the one before it.

    Click image for larger version. 

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    You don't necessarily need to assemble 6 stages. It depends on what range of voltage outputs you wish.

    Your specs ask for hundreds of mW. This requires sufficient Amperes going through all components need to be robust enough to handle Ampere levels.



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    Re: Capacitive Boost or Charge-Pump DC-DC Converter

    Thank you for your advise. the project specs is asking for hundreds of mW and producing at least 3V voltage output as it is for portable electronics. I also cannot use diodes in my circuit, i have to use mosfets



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    Re: Capacitive Boost or Charge-Pump DC-DC Converter

    Quote Originally Posted by WASDQWERTY View Post
    3V voltage output as it is for portable electronics. I also cannot use diodes in my circuit, i have to use mosfets
    Then do you have a schematic to start from, which uses mosfets?

    What is your power source? This creates a challenge for your project, because if you want 3V @ 400mW output, it requires a draw approaching 1 Amp from a 1.5V cell.



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    Re: Capacitive Boost or Charge-Pump DC-DC Converter

    i have to use an IC-design software which is Cadence virtuoso to simulate the circuit that i designed. Within the software i can place a DC source.

    I'll have to design the circuit from scratch using past references or research that is why i do not have a schematic.
    Click image for larger version. 

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    so far i've been reading up on this topology whereby i have to change the switches to mosfets

    - - - Updated - - -

    in this case, how do i determine which W/L to use for my mosfet



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    Re: Capacitive Boost or Charge-Pump DC-DC Converter

    Quote Originally Posted by BradtheRad View Post
    Then do you have a schematic to start from, which uses mosfets?

    What is your power source? This creates a challenge for your project, because if you want 3V @ 400mW output, it requires a draw approaching 1 Amp from a 1.5V cell.
    Click image for larger version. 

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    I've been reading up on this topologic where they advised my to reconfigure the switches into nmos or pmos. apart from this i will also have to design my own clk and clk bar signal.

    As i am still currently learning as a student, i hope you can understand that I do not know how to express my concerns properly due to the lack of knowledge. Thank you



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    Re: Capacitive Boost or Charge-Pump DC-DC Converter

    It's hard to be certain exactly who originated this charge pump topology (whether Dickson or Nakagome). To make some progress in this discussion here is my basic simulation showing how to connect transistors to the flying capacitor.

    Click image for larger version. 

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    This illustrates the concept.
    You need to add stages in order to attain 3V.
    You need to maximize efficiency if you want a few hundred mA.
    You need to design an oscillator that produces sufficient voltage to drive all charge pump stages.



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    Re: Capacitive Boost or Charge-Pump DC-DC Converter

    sorry, can i ask, in this case when I characterize my mosfet, what will my W/L be?



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    Re: Capacitive Boost or Charge-Pump DC-DC Converter

    While I'm inexperienced at IC fabrication, it's obvious there are hurdles because your transistors need to turn on with a small supply voltage.



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