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How to get charge pump voltage doubler's switch bulk voltage

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allan_guo

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Just as described in the pic:
My question is how to determine the bulk(S3,S4) voltage?
I want to get a regulated voltage vout:vin<vout<2*vin,so there maybe 3 different
voltage levels:vin,vout,v(A);to prevent leakage current,the bulk (S3,S4) must be connected to the highest voltage, I have done voltage selector of vin&vout, But
the duration of v(A) is quite shot,so can I do voltage select for the three voltage levels.
anybody can give some advice or so paper about this question?thanks a lot !
 

Re: How to get charge pump voltage doubler's switch bulk vol

Hi,
In your clocking scheme you would have to incorporate for bulk switching.
for S3 and S4.
I hope you are using PMOS for switching as they would pass a good one.
 

yes, you need a body switch to flip bodies from VA to VOUT and so on. This is usually just a simple high-side comparator that chooses the higher of two voltages, and muxes it to the output. Buf if you're already generating doubled clock signals, you may be able to use a copy of those.

But actually, isn't your doubling mechanism charging through S2/S3 and discharging through S1/S4? That would say that S2 is the only device that does not need a body switch, assuming PMOS/NMOS switches.
 

Re: How to get charge pump voltage doubler's switch bulk vol

thanks you two, there remain two questions:
1) In my circuit, S1 S3 S4 are all PMOS switchs.My new question maybe how to determine the source of S3&S4, I have seen a paper that S3's source is connected to A,S4's source is just connected to vout,is that right?
2)The work mechanism is just as electronrancher described. I have done bulk voltage swtiching, but just for vin&vout, the high voltage duration for V(A) is very shot and will come down soon when charging the vout , so if I do three voltage selecting,the comparator speed may be very high! The duration of V(A) is far more shot that my clock frequency, and if I have achieved this bulk switching, because of the fast change of V(A), the bulk voltage may oscillate.
 

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