Hi,
Would a potential current loop condition cause current/power waste?
In one board we have USB 5V boosted from battery PACK_PLUS to power USB peripherals when external USB 5V is not connected, as shown in the schematic.
However, this leads to mysterious current consumption when there is no USB peripheral connected, nor any IC in use connected to the OUT (pin 10 and 11) of bq24074. This happens when the to-5V-boost converter is on, and PACK_PLUS through it generate 5V USB power supply which at the same time is also connected to 13 INPUT POWER pin. The current consumption is very significant such that it is greater than 100mA for PACK_PLUS voltage range between 3.7V and 4.2V.
We strongly suspect that this was due to the internal current loop from [boost converter]→[USB-5V]→[bq24074]→[PACK_PLUS]. Although no USB peripheral is connected and no device connected to 10,11 OUT pin, from 13 IN pin to 2,3 BAT pin the current passes through the internal charger of bq24074 to charge the battery, and when doing this the current has to go through transistors within bq24074 which all have RDSon. Only this could possibly explain for the current loss when no load is connected.
There is a CEn(4) pin which we connected to GND. If we connected CEn to GPIO, and pull it high when PACK_PLUS is powering 5V USB supply thought the boost converter, would this disable the self-charging loop and solve the 100mA current leaking problem?
Paul
