Preface

TI BQ24075 Li-Ion Battery Charger is used in the VMU Zero V1. This device also integrates the power path management to supply regulated power to the system even the battery is depleted or detached.

Test Setup

Procedure

1. Slide the switch S1 to ON position to connect the battery
2. Attach USB cable and fully charge the battery
3. Probe VBAT and GPIO14 (TX) to monitor the system power status
4. [Test Case #1] Leave the screen at emulator selector

   Remove charger and plot the discharging profile

5. Charge the battery
6. [Test Case #2] Load Super Mario on NES Emulator and leave at demo
   Remove the charger and plot the discharging profile
7. Slide the switch S1 to OFF position to disconnect the battery
8. Probe VBAT and CHG# to monitor the charging status
9. [Test Case #3]  Leave the screen at emulator selector
   Slide the S1 to ON position and plot the charging profile

Results

Discharging Profile Case #1  - Idle at Emulator Selector

Discharging Profile Case #2  - Super Mario Bros on NES Emulator

It only lasts 20 minutes with the 150mAh battery. 500mAh battery will be considered for V2 design...

Charging Profile Case #3 - Idle at Emulator Selector 

Charing time will look very similar regardless of the tasks on the Pi unless total input current exceeds the limit of 1.3A which is configured at I_LIM pin.