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Li-po charging: system load in parallel with battery

Question asked by kwas on May 14, 2013
Latest reply on May 19, 2014 by Brad Stewart

Hi -


I am migrating a design from BQ24090 from TI due to the package size. I want to move down to a smaller package with a minimum of external components. The chip should charge a Li-Po battery (just one), and optionally power the system while charging.

With the TI chip I connect the system load in parallel with the battery. This is suggested on the spec sheet. However no similar reference design is printed on the freescale chargers I looked at (such as MC34673). The power comes from a USB port, if that matters. The microcontroller must know if the device is plugged into the USB port (/PPR pin provides this functionality so no problem there).


I should also specify that I have an LDO regulator downstream of the battery, so strictly speaking it's the LDO that is in parallel with the battery, and system load is powered from that (however _some_ peripherals such as motors etc. are powered directly from VBAT).


So the question is, let's say I use MC34673. I just connect EN to VIN, BAT to the regulator input, leave FAST disconnected, and connect PPR to a microcontroller input pin.


Ahia or nisch nisch?