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BQ24210 - DPM feature

Huzefa Siamwala
Prodigy 30 points
Other Parts Discussed in Thread: BQ24210


Hi I am considering BQ24210 for a Solar Li-ion charger I am designing. The panel is 1A, 5V.

Some questions:
1) is input diode required?
2) why is the min voltage 3.5v? I mean how can the charger work on 3.5v

Quote from datasheet: This prevents a source with voltage less than VBUS-DPM to power the BAT pin. 

I don't get this.
3) The issue we have here is that the voltage collapses during high current draw. We need to find a way to keep the lipo charger from drawing too much current, and backing off when the voltage starts to droop. We can set the voltage to a point just above the battery charge voltage point (say 4.5V) and then instruct the charger to draw as much current as possible. It will automatically increase/reduce the charge rate to keep the voltage higher than 4.5V!
This way I can get near-MPPT performance, without the complexity of a DC/DC converter, and without the high price.
4) Quote from datasheet: If the VDPM pin is floated (open circuit), the IC operates in Battery Tracking Mode. In this case, VBUS DPM threshold is internally set as VTRK, which is typically BAT+100mV (BAT>3.65V) or 3.75V (BAT≤3.4V).

I don't understand what use is battery tracking mode. We need to keep the voltage above battery "charge" voltage, not above the bat voltage.

Thanks for your help.
Huzefa
  • 0
    TI__Mastermind 31120 points

    a1) not sure what input diode you are referring to.

    a2) The charge can provide current to the battery when the battery voltage is lower than the input voltage.  When this is the case, the lowest voltage the input can be loaded to is ~3.5V.

    a3) The DPM resistor sets the regulated input voltage, such that the charger will not deliver too much current to pull the input below the input DPM set threshold.

     

    4a) You have a good point.

  • 0
    Prodigy 200 points

    Hi Huzefa,

    Can you tell me from where did you get the 5V 1A panel?

    Thanks and regards,

    Shahbaz sarik