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BQ24133: Charge Current, System Current, and Input Current Concerns

Part Number: BQ24133

I see there is a maximum recommended charge current, 2.5A, but what about minimum current? We are hoping to use a total input current of about 300mA. Our load or system, will draw about 100mA. This will allow 200mA to be used as our charge current, Is this possible? It seems that it would be a minimum charge current of 600mA, since we can't have a value for V-ISET lower than 120mV or the charge is disabled. So based on the calculations I could set 120mV on this pin and just set pin V-ACSET also to 120mV, which will give me a total input current limit of 300mA. This 300mA input current limit will force my charging current to be 300mA minus my load current, correct? This should in theory cause my charge current to be forced to 200mA, while still maintaining the requirement of having V-ISET to at least 120mV.

  • Hi Miguel,

    If you increase Rsr resistor, then the V(ISET) will be higher than 120mV. Since the charge current accuracy is based on the voltage across Rsr resistor (see Kiset, Kiprechrg, Kitem specs on datasheet page 7-8), I recommend that you increase Rsr based on your accuracy requirements.

    Can you provide more details about your end application (input source, required system voltage, etc.)? Perhaps there is another charger that would work for better for you.

    Regards,
    Jeff