-100V generation max 1846 IC.

[themaccabee]

Hi,

I need to design a -100V output from 4.5 to 5 V supply output current required is close to 1mA.The IC should operate on Fixed PWM.No transformer is prefered.

So i was looking towards inverting buck boost topology & is examining the IC MAX1846.
There are two problems im facing..

1)Since the current requirement is too low.Will it cause any kind of problem.?(while calculating with the Maxims online simulation tool.It complained 1mA is too low current ,minum required is 60mA..)

2)It is a current mode controlled IC.I dont know pretty much about the compensation values and all.So is it safe to use what the typical online simulator gives??

Thanks

 

[rhaynes]

Go ahead and let it create the schematic at 60mA. Then to scale the current down by a factor of 60 increase the size of the sense resistor to 3000mOhm (3 Ohms) and change the output load to 0.3mA ramping to 1mA. Since it's an external sense resistor the chip won't be aware that the current has changed from the 60mA and I think probably would work fine but may be a bit of overkill. And I would want to figure out where that original 60mA limit is coming from before committing on this circuit.

As for transient load response you would want to change the simulation to more closely match your transient load conditions to test the response.

Ray