LT3652 with small voltage solar panel

Hi all, 

First of all thanks in advance for your reading and help.

I've seen from LT3652 datasheet that VIN must be VBAT(FLT) + 3.3V in order to startup correctly. What does that mean practically ?

Let me explain why I am confused :

I have a LT3652 to regulate a small voltage solar panel (it has its maximum power point at around 6V and can climb up to 9V when fully illuminated). It would charge a 1S2P Li-Ion battery pack (4.2V VBAT(FLT)).

I don't know at this point what will happen when, in the morning, the sun will rise and the solar panel voltage will be under the condition of (VBAT(FLT) + 3.3) (7.5V).

During a sunny day the condition will be fulfilled: VIN will be >7.5V because there will be no load on it (it could even go to 9V). Then, I expect the LT3652 to start charging and start regulating, so that VIN never goes under 6V. Is that possible ? 

My question is : how will the LT3652 react during the time where VIN < 7.5V ? It's not mentioned and I am wondering if there could be any issue preventing my circuit to start charging correctly.

Again, thanks a lot for the help.

Best regards,

Loïc

Parents Reply
  • +1
    •  Analog Employees 
    on Dec 9, 2020 8:10 PM in reply to Laoky

    Hi Loïc,

    That depends on a few factors as well, most notably the charge current (since the internal switching transistor's voltage drop changes accordingly). You should have at least 1V of margin. That is of course on the charger side of the VIN blocking diode.

    Regards,

    Zack

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