rhildinger wrote: ↑
Tue Feb 04, 2020 4:24 pm
Should I be concerned about this LCD drawing up to 500 mA through HDMI?
Earlier Pi, for example 3B+, used a RT9741CGV high side switch to supply 5V via HDMI pin 18 which is rated at 700mA. It is not clear what the Pi 4B uses because that is not shown on the reduced schematics. And, even if the same, that the device is rated to carry more than 55mA, it does not mean that it will or higher than that should be drawn. Drawing too much current could cause the device to overheat, shut down, or potentially be damaged.
Additionally the RT9741CGV includes VOUT clamping to 0V which isn't ideal if the LCD is supplying power through HDMI when separately powered so it may be advisable to disconnect the 5V wire in the HDMI cable being used. That may well be the same for the 4B.
Note 5V is on pin 18 for full-size and mini-HDMI connectors, pin 19 on a micro-HDMI connector.
Drawing current for an external monitor will of course reduce the current available for other things you attach to your Pi.