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