VIPER 06L for 3.3VDC

[ahmed239955_st]

Posted on April 13, 2016 at 19:13

Hi, I am using the eDesign Suite to make a 3.3VDC Power Supply , but I am facing some problems .

First of all , I got the schematic from the eDesign Suite and make it on Breadboard , It should has an output of 3.3VDC but I had 1.51V !!.

So I decided to change the design to get 3.4VDC instead, After Implementation of the new circuit on a Breadboard also , I got 3.45VDC at the beginning but after a while the output voltage is 6.3VDC !!

Also it has a very limited output current , the output voltage decreases as I connect a load .

After all of that I have decided to use a new design , so I have changed the specification of the converter to be 3.5VDC , But the schematic has something wrong , It does not show the capacitance of Cfb !

Thanks for your help.

#viper

[Patrizia BELLITTO]

Posted on April 14, 2016 at 16:51

Hello,

we are sorry but there is an error in the schematic, the capacitance Cfb should not be present.

About the other issues, the engineer responsible for VIPer applications will answer you as soon as possible.

Best regards,

Patrizia Bellitto

eDesignSuite developers team

[ahmed239955_st]

Posted on April 18, 2016 at 21:19

Do you mean there is no capacitance on the feedback pin ??

Waiting for technical support asap .

Thanks

[Nickname7392_O]

Posted on April 19, 2016 at 14:32

Hello,

when setting such a low output voltage value I suggest to use X version (30kHz) instead of L, in order to avoid that, due to the large input to output difference, the Ton required to keep the output under regulation could fall below the Tonmin of the device (the duty cycle is: Vout/Vin=Ton*fsw). In such cases, the system will skip cycles and this could have an impact on the output voltage ripple.

It’s not clear the reason why the output goes from 3.45V to 6.3V, how long does it take to obtain this, and with which output load? I should have a look at waveforms.

What about the behavior of the board with setting at 3.5VDC? 

[ahmed239955_st]

Posted on April 19, 2016 at 16:42

But the Designer suite did not mention any limitation about the min Ton .

Anyway, I cannot find a circuit for 3.5V output , because the eDesigner Suite does provide a schematic like the one above (with a feedback capacitance of Cfb!)

If you can provide me with a schematic I can give it a try . 

 

Also I have tried to disconnect the Feedback pin from the circuit and the voltage remains the same at 6.3V. What happens is when I connect the ac line the voltage rises from 0 to 6.3V in about 2 Seconds !

Also I cannot try with the Viper X because I have no schematic and the eDesign suite has the same error with the feedback capacitance