Hi!
I´m building a 3A 12V battery charger, using the UC3906.
If I understood the datasheets correctly, with Imax = 3 A, Ioct needs to be about 0.3 A in order for the circuit change from overcharge to float mode. But what if there´s a permanent load drawing more than 0.3A from the battery? In that case, the UC3906 will never bring the battery to the float state.
Application note U-104 and bq24450 datasheet says that it is possible to change the ratio Imax/Ioct by using two series resistors for the current sense, instead of just one. The problem is that there´s a lack of consistency between these two documents.
U-104 application note (page 3-82), shows one possible configuration, and some correspondent equations. It is stated that Ioct = 25 mV divided by RS1.
bq24450 datasheet shows the exact same circuit (page 12, figure 9a), but it says Ioct (here called Itaper) is equal to 25 mV divided by RS2.
Two datasheets show the same circuit, the same configuration, but the equations are different. Could it be a typo in one of the documents?
Thank you for your attention!