ADP5070 output mismatch

Hi Joonash, 

The other channel of ADP5070 is a boost converter, so you can't make its output voltage lower that the input voltage, i.e 5Vin to 2.5Vo. If you want to implement this on ADP5070, then you should configure it in SEPIC mode (see page 25). Thank you. 

Regards, 

Fritz

Thanks for the quick reply.

I can do the changes to schematics, but is there instructions how to calculate values for CS1, L1A and L1B inductors? Or would these be the same as calculated for Boost/Buck topology?

Thanks in advance.

You can use the ADIsimPower tool for ADP5070 which can be found here: (+) ADIsimPower Design Tools Download - Documents - Power Management - EngineerZone (analog.com)

Thank you. 

Regards, 

Fritz Cyrill Gonzales

May I know the estimated annual usage and the end application of this? 

Actually I have tried to run that ADIsim but it only gives that Boost mode not SEPIC. Also giving an VBA error although I have enabled macros. Is there any other way to calculate needed components?

Annually some tens of parts needed max 100pcs.

What are your input and output current specs? I'll try to input them on my tool. It works fine on my side 

Have you tried to enable the macro on excel? 

Yes I have enabled macros. Probably something still wrong with the settings.

Can you run with the above specs and printout the BOM list having CS1, L1A and L1B.

Kindly see attached file for the auto generated design from simPowerTool.

Can you try to enable the developer tab? Once enabled, it must appear on your excel tabs and see if the tool will work.  

PDF

I have Developer tab always enabled. Run Time error 13 doesn´t tell me much and I cannot open the VBA scripts because of password protection.
Seems that the tool or company privacy will cause unwanted issues that are impossible to solve. Anyways I appreciate above auto generation by that I can try to continue fixing the error.

I´m using Excel 2016 version, could that be possible issue because Tab "Enable Macros" doesn´t tell anything about it. Macros will anyhow work because I can make changes to design criteria. 

Yes. It could be due to your company's security. Btw, I noticed that I inputted -5V on the other channel instead of -2.5V. See attached file for the correct inputs.

PDF


Anyway, kindly let me know if you need anything else. I would be happy to help!

Regards, 

Fritz

Yes. It could be due to your company's security. Btw, I noticed that I inputted -5V on the other channel instead of -2.5V. See attached file for the correct inputs.

PDF


Anyway, kindly let me know if you need anything else. I would be happy to help!

Regards, 

Fritz

Hi,

Thanks for the update. I was just going to ask that why my calculations gave -5V but here´s the reason. I have tried to update buck/boost implementation to SEPIC one but sometimes it gives +2,5V and -4,3V in witch the negative voltage FB2 pin gives 0,4V. This should be 0,8V but I don´t get the root cause for this yet. Any idea where to look issues?

Hi, 

Can you try to check the switching frequency waveform and the duty cycle first? If both parameters are normal, then I would assume that there is something wrong with the values of your feedback resistors.

Also, try to check what happens to the output voltage if you put the negative rail in light load. Would be great if you could give me startup waveforms during light load and full load.

Let me know the results. Thank you. 

Regards, 

Fritz Cyrill Gonzales