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Original question:

LM2665: What's the maximum output voltage when using cascading design

LM2665: LM2665

Gaurav Mayekar
Prodigy 60 points
Part Number: LM2665


Hello TI Team,

We trying to simulate LM2665 IC based voltage doubler circuit on WEBENCH but it is not supported. See below screen shot of issue.

  

We simulate below circuit using this LM2665 IC.

 

Please support this issue. or please provide simulation result.

Input voltage 4.5 to 5.5V

Output voltage 15V 

Output current 50mA 

Or please provide any other low cost solution (as similar cost of LM2665 IC cascading circuit). 

Regards 

Gaurav Mayekar

  • 0
    TI__Guru 67515 points

    Hello Gaurav,

    Charge pumps are very simple devices, so we do not have simulation tools for them, especially when they are older.

    In the above configuration, LM2665 is operated as voltage doubler and as they are cascaded in this case, the output voltage is roughly 3 times the input voltage. In general there are some losses in the system, so it is not fully 3*VIN. So it depends on the voltage needs on the 15V rail if it works out or not. A rough estimation would be a loss of 0.5V per converter, so the output voltage based on your input would be roughly between 4.5V*3-1V = 12.5V and 5.5V*3-1V = 15.5V. So the variation in the input changes by a factor of 3 on the output. This is how a non-regulated charge pump works in general. So for a more accurate VOUT, you need a more accurate VIN for a simple doubler charge pump.

    If this is not good for your application, a small boost converter would be the better solution, I expect.

    Best regards,
    Brigitte