What is the importance of the 0.5-ohm cable resistance for 5W charger applications

Hi,

Many IC products for chargers have built in cable compensation. Charger output automatically increases with load to compensate for cable drop so that the load receives well regulated voltage.

The cable compensation built into the parts is often based on the cable drop for the cable to be used with the charger.

Hope this helps.

Cable loss is also a factor as it affects overall efficiency. 

Regards PI-Sarek

Hi,

Thank you very much for your prompt reply.

As a charger designer, do you worry about that or is it automatically taken care of in the switching IC itself.

I am little baffled on how they compensate it since there is no feedback from the load. It seems the only plase you can regulate to is at the output of the charger itself. Just curious.

Thanks again. 

The output of the charger is regulated however the voltage is adjusted as a function of current so as to provide "cable compensation". This works as long as the compensation being offered matches actual cable drop.

Customers typically ask for parts that will have 6% cable compensation. what that means is that the controller will automatically adjust output voltage as a function of load current such that the voltage at the output of the board will be up by 6% by the time the charger goes into CC mode of operation. customer ordering such a part will need to ensure that their cable in turn has a voltage drop of 6% when operating at rated current for CC mode operation. I hope this clarifies

Regards,
PI-Sarek

Thanks a lot for the clarification. Makes sense.
Essentially, it's an open-loop calibration assuming a 6% drop at the rate CC mode operation.
Thanks again.