Hello
I have to electronic circuit boards, on acts as a controller and the other as a display panel.
I want to disable the buffer IC on the display panel until the controller is connected and powered.
I added a simple transistor switch to the enable pin of the buffer so it is pulled high unless the 3V3 from the controller is connected through a cable in which case the transistor will turn on and enable the buffer.
When I power the display panel and connect the data cable from the display panel to the controller I get about 1.5V on the input of the transistor even though the controller is unpowered and I cannot work out where it is coming from.
I cut the 3V3 track going from my switching regulator to the associated pin on the connector of the controller and the input signal of the transistor went low as expected.
Please can someone help me understand where this mysterious 1.5V signal is coming from? I even tried connecting the transistor input signal to another logic IC and got the same result.
I also tried adding pulldown resistor to input of transistor but still it is getting pulled to 1.5V from somewhere.
I have to electronic circuit boards, on acts as a controller and the other as a display panel.
I want to disable the buffer IC on the display panel until the controller is connected and powered.
I added a simple transistor switch to the enable pin of the buffer so it is pulled high unless the 3V3 from the controller is connected through a cable in which case the transistor will turn on and enable the buffer.
When I power the display panel and connect the data cable from the display panel to the controller I get about 1.5V on the input of the transistor even though the controller is unpowered and I cannot work out where it is coming from.
I cut the 3V3 track going from my switching regulator to the associated pin on the connector of the controller and the input signal of the transistor went low as expected.
Please can someone help me understand where this mysterious 1.5V signal is coming from? I even tried connecting the transistor input signal to another logic IC and got the same result.
I also tried adding pulldown resistor to input of transistor but still it is getting pulled to 1.5V from somewhere.
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