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BQ24210 - Suitable Solar Panel Select

hayrettin erturk
Prodigy 90 points
Other Parts Discussed in Thread: BQ24210

Hi,

I read the documentation and quite qood understand the datasheet of BQ24210 and I researched all the topics about it in forum but one point is not clear on my side.  Now my point is:

Considering working range of 3.5v - 7v, is the solar panel MPP should near below 7V ? In this case max. open circuit for a solar panel should be 8.75V (assuming 80% MPP). Am I right In this point?

If I am right then the selecting resistor for VPDM formulation is quite looks limited with range 1k-10k Ohm and in this case VBUS voltage should between 3.65V-5V. So how one can calculate for near below 7V?

Am I missing something or the chip actually setted up for VBUS 5V anyway? In this case max. possible voltage for a solar cell should be around 6V considering its MPP. Is this right?

  • 0
    TI__Guru*** 143910 points

    The IC maximum operating voltage is 7V.  If VBUS is above that voltage, the IC's OVP circuit will turn on and shut down the IC. The VDPM circuit sets the MPP point (called VBUS_DPM in the datasheet). The equation for setting the MPP point to a voltage higher than the internal offset voltage (called VBUS_DPM_1)  using a resistor on VDPM pin (RVDPM) is at the bottom of datasheet page 14. If you set the VDPM voltage above 7V, the IC will not function.

  • 0 in reply to Jeff F
    Prodigy 90 points

    Yes, equation is defined in page 14. But if I'm not missing something; at electrical characteristics list at page 5, KVBUS_DPM term factor defined for VBUS=5V and R= 1-10kOhm range. 

    In this case, if I choose for example 6V for VBUS_DPM then RV_DPM becomes 16kOhm. And according to specified range this value is out of  that range.

    What am I missing here? Is this equation only linear for that range but usable for closer values?

  • 0 in reply to hayrettin erturk
    TI__Guru*** 143910 points

    The VINPDM is only characterized for values up to 5V.  Assuming the solar panel has the typical V(MPP)=0.8 x VOC, you could choose a solar panel with 5V/0.8 = 6.25V VOC.

  • 0 in reply to Jeff F
    Prodigy 90 points

    Thanks, that was the answer that I'm looking for. But it would be good if that was more clearly stated on datasheet. Since this is IC maybe not only but has a purpose for solar applications.

  • 0 in reply to hayrettin erturk
    Prodigy 10 points

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