Switchover transistor and DCDC_EN FET can't coexist - need to add Schottky diode

[CRImier]

The switchover circuit on Delta boards doesn't work as expected - the DCDC_EN is supposed to both control the FET that's switching the 5V DC-DC on and off, as well as the transistor that's enabling the switchover circuit. However, in practice, the transistor pulls DCDC_EN down when it's not yet configured as input - from the moment the phone (and MCP23017) is powered, till the moment the 5V DC-DC is first enabled/disabled (at that moment, the software sets the DCDC_EN GPIO as output). We could workaround that in software, but it's a hack. Instead, I came up with the following solution:

• The transistor (that enables the switchover) is controlled from the charger input (through a 10K resistor) instead of DCDC_EN
• A signal Schottky diode is added, pulling the transistor's base down whenever the DCDC_EN is low (and, consecutively, DCDC is enabled)

This enables the switchover when the charger is connected, but disables the switchover whenever DCDC is enabled.

The problem is - we need to add another BOM entry, as well as source another component. Therefore, if any other ideas are proposed, I'll be happy to hear them.

[CRImier]

For now, the Schottky solution is implemented.

[CRImier]

Works!