Rev 2

This revision only added the ability to charge the battery through the BeagleBone Black but this required several changes to the hardware design. We’re currently awaiting the shipment of this board.

First, we needed to remove the barrel jack that was used in Rev1 because when the 5V barrel jack was connected, the battery was completely disconnected from the circuit, preventing power from flowing in either direction.  The next major change was the addition of a supervisor chip (TPS3700).  This chip monitered the 5V barrel jack and output a high voltage when it was connected.  This did nothing to prevent a power collision however, so several P-channel MOSFETs were added to disconnect the parts of the circuit that were being powered by the battery.  The gate for these MOSFETs was connected to the output of the supervisor so that when the output was high, the MOSFET would prevent current flow.  A MOSFET was also used at the input for one of the LED drivers to indicate whether or not the battery was powering the phone.

The BeagleBones PMIC allows for battery charging without any software initiation.  This means that as long as the battery is connected to only the PMIC  while the barrel jack is plugged in, it will charge.

A video explaining the schematic for Rev2 can be found in the under Design->Demo Videos

Special thanks to TIer Ryan Eslinger

SCH_led2

LED Driver

 SCH_rev2

Power Circuitry

PCB_rev2

PCB Layout

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