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hardware/xs-ctrl: Add issues/reworks for VBUS detect 

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
master
Sylvain Munaut 2023-03-13 21:45:36 +01:00
parent cb8197a6c7
commit 0aa54bc297
1 changed files with 14 additions and 0 deletions
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hardware/xs-ctrl/ecn.md
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@ -29,6 +29,15 @@ Two of the boards were assembled and tested.
* The `CHG_FPGA_n` line through the LED
* The `SENSE` line from the voltage divider
* Voltages on the USB lines (most importantly through the pull-up) end
up leaking on the 5V rail through the ESD protection diode, which in
turn causes the `SENSE` line to be triggered ...
I think ideally the pull-up from the FPGA should actually go through
and external NMOS that enables pull-up from 5V rail.
* The 5V rail doesn't drain when disconnected.
* The soft-off circuit wouldn't actually turn-off.
* When the battery is not connected, the system can't be operated. The
@ -60,6 +69,11 @@ boards.
may need an active discharge resistor to make sure the gate discharges
when USB is disconnected. Not tested.
* Cut the 5V rail from the ESD diode to prevent voltages on the data line
to leak to an un-powered 5V rail.
* Added a 1M pulldown on 5V rail so it discharges.
* Replaced C14 with a 2.2uF cap in parallel with a 100k resistor.
This makes the `PWR_EN` line only raise to 1.6V which is enough to enable
the regulator but makes it easier to discharge without it re-triggering.