internal supply voltage generation

[naisare]

I am struck in the design of boost converter. :!:
this is a switched capacitor type of boost converter.
My input voltage is a single battery supply, 1.2V.
With this input voltage I canot design most of my internal blocks
like bandgap,comparator, oscillator..etc. The mos is 3.3V mos
So, I need to design an internal supply voltage of 3.3V.
Anybody faced this problem?
The output required is also 3.3V regulated.

 

[sunking]

YOu can design a charge pump first with 3 times.

 

[jordan76]

One thing you had better keep in mind:
Be careful about the current driving capability of the charge pump.
If too much, the power efficiency will be much worse. In this case you may have to choose other methods.

regards,
jordan76

 

[naisare]

How to generate the gate-drive signals for the switches of charge pump, whose voltage level should be higher than the available 1.2V?

 

[sunking]

you can use pmos as switch. so the gate is need 0v

 

[Fom]

If you will not use Flip-flops with pass gates it should be OK. Simple logic like invertor, nand and nor can operate may be less than 1V (depends threshold voltages).

 

[naisare]

you can use pmos as switch. so the gate is need 0v

Pmos will be on for 0V, fine, but it will not be fully off when its gate is at 1.2V and the drain at 3.3V.
Moreover, PMOS leads to very high size, since the load current is 100mA.

How about dynamically changing the gate drive voltage level of the switch as the output voltage builds up. Any thoughts on this??
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