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ldo design operating in wide range supply voltage (2~6V)

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ella1923

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Hi,

I'd like to know design considerations of ldo, this time operating in
wide range supply voltage (2~6V). Load current is just several
hundred uA. Do I still need wide swing opamp for this? How to
avoid breakdown?

Thank you very much for any ideas.

Ella
 

chris.mourad

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Hello

What is the breakdown voltage of the devices used in your models? What do you mean by "wide swing opamp"?

Cheers
 

ella1923

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Hi chris.mourad

Breakdown voltage is 3.6V. I mean wide output swing opamp, perhaps still need to use this.

When ldo is in 6V supply, gate voltage of the power mosfet goes almost to VDD considering
no load condition. The output of the error amplifier will have breakdown issues since I can't
cascode too much because I am considering the 2V supply which also needs enough headroom.
The ldo should work at 2V supply as well as in 6V supply. Any experience or idea about this kind
of design?

Thanks a lot.
 

chris.mourad

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Hello Ella

with 2V you can cascode 2 VDS + 1 VGS??? If ok, the output stage of your error amp will be a common source transistor, a cascode and a diode connected P-type transistor to control the gate of your power mosfet...

I already designed LDO's working from 1.8 to 5V, working pretty well...

Cheers
 

mike.zhang

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Hello Ella,
Maybe u should choice the other process, in which the breakdown voltage is more than 6V.
 

ella1923

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chris.mourad:
i had the idea of clamping & have found similar design too..but i'll try your suggestion..
i had the hard time designing voltage reference that works in such a very wide range
supply voltage :( .. do you know any simple ckt structure how to regulate voltage?

mike.zhang: this is the least thing i can do :(
 

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