LV2862: Maximum Capacitance Value

In other word, " Is there a maximum capacitance limitation for LV2862?"

Thanks.

Hi Nakano-san,

Can you specify your operating conditions? 

The LV2862 has internal soft-start, so the maximum capacitance you can end up using will be the one that will not allow the part to enter overcurrent upon start-up. I would recommend picking a converter that allows for adjustable soft-start. That way you can adjust the soft-start timing so that you can use the 1000uF load capacitor. 

Regards,

Richard

Hi. Richard-san,

Thank you for your reply.

>Can you specify your operating conditions? 

Yes,  as follows:

VIN min18.0V -- max 37.0V

VOUT 5V, 0.2Amax

I hope those are helpful for you. If you need more information, please let me know.

Thanks.

Best Regards.

Hi Nakano-san,

May I ask why did you choose such a large output capacitor? Are there any special application requirements? Because the ESR of a 1000uF electrolytic capacitor will be large. The formula for the selection of the output capacitor is given in the datasheet.

I use webench to simulate according to the conditions you gave, and the results are as follows:

https://webench.ti.com/power-designer/switching-regulator/customize/23?VinMin=18&VinMax=37&O1V=5&O1I=0.2&base_pn=LV2862XL&AppType=None&Flavor=None&op_TA=30&origin=pf_panel&lang_chosen=en-US&optfactor=3&Topology=Buck&flavor=None&VoltageOption=None 

Maybe you can check it. Thanks.

Aurora

Hello, Aurora-san,

Thank you for your reply. In fact , the circuit that I am designing, has original design.

Of course the DC-DC converter IC is not a product of T.I.

The original circuit  was  designed more than 5 years ago, and it uses 1000uF.

The 1000uF is not only for DC-DC converter output stabilization, but also because it is necessary to maintain the 5V voltage to some extent after the power is turned off.

Because the original IC(not TI) is no longer available(due to E.O.L), so  I would like to replace it with a TI's product.

The previous circuit uses an converter IC with a package and pinouts similar to the LV2862 (also LMR16006).

So it may be necessary to change some passive components value, e.g, feedback R, or L values, but I thought it might be possible to use it without changing the pattern.

I thought no pattern changes can reduce development time and costs.

That is the reason why I chose LV2862 this time for a circuit with 1000uF output capacitance.

If the circuit using LV2862 really cannot accept with 1000uF, I will consider lowering the value of 1000uF.

Even so, if possible, I don't want to lower it too much from 1000uF.

Thank you for your cooperation.

Best Regards,

Hi Nakano-san,

According to your description, I suggest that you can refer to what I said earlier to select the appropriate output capacitor value according to the datasheet and webench. You can also download the pspice model on the official website for simulation verification. Hope this helps you. Thanks.

https://www.ti.com/lit/zip/snvmc13 

Aurora

Hi, Aurora-san.

Thank you for your suggestion and SPICE model file.

By summarizing your feedback and opinions,I thought that the best solution for this problem would be to do a simulation  or actually experiment.

So I decided to experiment,  LV2862( and also LMR16006) converter prototyping with 1000uF.

I would like to judge by the result.

Thanks a lot!

Best Regards,

Hi Nakano-san,

Ok. Looking forward to your feedback. Thanks.

Aurora

Hi Nakano-san,

Thank you for your test results. This will help others with the same need. 

Aurora