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Charge pump topology

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bharath_k

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Hi everyone,

I have a task to design a charge pump to generated a output voltage of 3.3 V from 0.8 V supply with load current of 8 mA in 22nm technology. I started off with a Dickson charge pump and also tried pelliconi charge pump. But in both cases the output current is in micro amperes range. I am using 1Mhz clock and 10pf Cfly. Can anyone please suggest me a better topology to maximize my output current and any design methods which I should follow.

Thanks!
 

charge pump
...
0.8 V supply

It's a challenge since you want to build an oscillating circuit which avoids the use of diodes because they subtract from output voltage.

This simulation is a voltage doubler which works with transistors, and 0.8V supply. It illustrates what's possible if it could be adapted to your spec 22nm.

astable H-bridge 6 transis 1V supply 2 cap V dblr 300 ohm load gets 1_8V.png

The stacked capacitors receive alternating current at the center of an H-bridge (consisting of the two rightmost half-bridges). Each capacitor acquires supply voltage.

Clock signals originate in the left H-bridge (consisting of the two leftmost half-bridges).
Thus the middle half-bridge does double duty.

- - - Updated - - -

Conceivably you could install an identical voltage doubler where the load is, thus making a self-oscillating voltage quadrupler, from a 0.8V supply.
 

Hi Brad,

Thanks for your reply. May be I didn't explain my application clear. I don't want an oscillating circuit. I want a DC-DC converter. The application where this charge pump to be used is for Neurostimulation.

Thanks.
 

This voltage multiplier is a Nakagome type. Capacitors charge in parallel, discharge in series.

Additional stages can be added until output is 3.3 V to your load. This schematic is a tripler, to demonstrate how stages are cascaded. The method is to attach half-bridges in combination. It may be possible to get correct bias for each transistor by tapping for voltage changes at strategic nodes.

Nakagome tripler clk-driven 500kHz 2 caps 7 transis 0_8V supply.png

Clock pulses are applied at left (which you shall provide since you claim you don't need an oscillator).
 
Thanks a lot. I will work on this and let you know the result.
 

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