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BQ25505: Peak input power?

Part Number: BQ25505
Other Parts Discussed in Thread: BQ25570

Hello,

The datasheet for the BQ25505 says the peak input power is 510mW. It also says the cycle by cycle limit of the charger is 285mA max. If V_in is 3V and I_in is 0.285A, then the power input is still 0.86W.

In an answer to a similar question posted here, it was said that the current would be limited by the BQ25570 chip. So is it safe to assume that the BQ25570 chip will limit it's own current, with respect to the voltage to prevent itself from damage? (i.e limit it's current consumption such that the peak input power is < 510mW regardless of input voltage?)

What we are trying to do is use a solar panel that has a Vmpp of 4.5V and a Impp of 205mA. So the Pmpp of the panel will actually be 910mW. Could this be damaging to the BQ25505? The V_oc of the panel will be less than the chip's maximum input voltage.

Kind Regards,

P

  • Hello P,

    The peak power rating is with respect to the maximum input voltage and current rating on the BQ25570. 

    The part does not limit the current with respect to the input voltage. It only limits the cycle by cycle current limit, which would result in an average current of ~115mA (typ). 

    In your case, if the VMPP is 4.5V, then the input power it will provide is 4.5V*0.113A=0.509W

    As far as the VOC does not exceed the max input voltage, it should be fine.