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iMX28 charger appears to have too much voltage drop

Question asked by Kölbl Michael on Mar 21, 2014
Latest reply on Apr 9, 2014 by jamesbone

We're using the embedded iMX28 charger to charge a LiIon-battery. As it is a large battery we want to charge with 400 mA, drawing 600 mA from VDD5V as we need about 200 mA for the board itself (iMX28 + peripherials). Due to the voltage drop on the USB cable we have only 4.75V at the iMX28 (measured nearby the BGA ball). But with 4.75V - the specified minimum voltage in the iMX28 data sheet - the iMX only draws 400mA from VDD5V, delivering about 200 mA to the LiIon-battery, which had 4.0V at the measuring time. When I increase VDD5V so that I have 4.85V at the iMX28 VDD5V current increases up to 600 mA.

 

Has anyone an idea or had seen the same effect?

Thanks, Michael

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