LM2611: Output 100mA from an input of +9V and output of -30V

Hi Danilo,

I guess that it can work.

I will have a closer look at it and come back to you tomorrow.

Regards,

Harry

Hi Harry,

We will wait for your update. Thanks for your help.

Regards,

Danilo

Hello Danilo,

As per a quick sanity check (without calculating every parameter in detail), I can tell the following:

- The selected Voltages are within the limits
- To convert 9V to -30V, the duty cycle will be around 78%, which is also within the limits.
 - The question is, if the internal FET can handle the peak switch current (see chapter 7.3.3 in the datasheet)
        For Grade B parts the minimum is as low as 0.7A, for Grade A parts it is 1A 
        (The typical numbers are higher, but I am looking at the worst case scenario.)

The datasheet also states:
- The design of the LM2611's internal compensation assumes L1 and L2 are equal to 10 to 22 μH, thus TI recommends staying within this range.
- The switching frequency fs can vary between 1.0 and 1.8 MHz, dependent on the particular device and the temperature.

When I use the worst case parameters for the equation in chapter 7.3.3, I find that Isw(peak) would exceed the limit of the Grade B part.

But when using a Grade A part it should be possible, as long as the value of the chosen inductors will be high enough.
Please remember to add some margin as well, to avoid that the inductors will go into saturation and to compensate for aging of the capacitors etc.

Best regards,
Harry.