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Moved]: DC DC Converter parameters

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gkkrish52

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I want to build a switched cap step down converter with CG 1/2. I dont know how to choose transistor size and flying capacitor size along with frequency. Any one familiar with this issue? Help needed
 

crutschow said:
What are the voltage and current values
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Dear Crutschow,

The supply voltage is 3.3 V and Load current is 1 mA. Output voltage is 1.65 V. I am unable to select the strength for the switches and size of capacitors
 

Hi,

what voltage drop is tolerable and what switching frequency do you use?

"strength of switches"
I don´t think this is a technical terminology
You mean ON-resistance?
--> voltage drop = resistance x current. Mybe you need to take duty cycle into account.

"size of capacitor"
capacitance.
The higher the capacitance the less ripple voltage.
delta_V = t x I / C
t = time where the capacitor needs to supply the load current
I = load current
--> the higher the frequency, the smaller the capacitance you need. The higher the allowed ripple voltage the smaller the capacitance.

Klaus
 

Klaus,

Tolerable voltage drop - do you mean voltage ripple? it can be 1-3 mV.
The strength of the switches - on resistance - I dont know how to choose the aspect ratio W/L for the switches. Can you explain the relation between duty cycle and the switch width.

Thanks for your help Klaus
 

HI,

I assume you posted in the wrong section.
Is it a power application? Or are you designing an IC?

Klaus
 

Hi Klaus,

I am design dc dc converter as a part of power management block in an IC. Sorry if i have posted in the wrong section.

Gopal
 

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