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min current needed for sinking current 8051

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neo_star

New Member
i am doing a project in 8051 in line follower.
it needs to sense the light and dark lines.
i am getting good voltages such as +5 for on and .32 v for off.
but the current i get is 5.5 micro amps during on and .7 micoamps during off.
is this current enough for the micro controller to sense the logic states
 

BeeBop

Active Member
i am doing a project in 8051 in line follower.
it needs to sense the light and dark lines.
i am getting good voltages such as +5 for on and .32 v for off.
but the current i get is 5.5 micro amps during on and .7 micoamps during off.
is this current enough for the micro controller to sense the logic states

Logic states are not dependent on current, so you should have no worries.
 

MikeMl

Well-Known Member
Most Helpful Member
I'm assuming (without looking up the 8051 spec sheet) that it has normal CMOS inputs. If so, the external circuit only has to supply normal ~few nA leakage to the input pin to guarantee a ONE or a ZERO.

The capacitance on the 8051 pin is about 10pF, so if your circuit is switching rapidly, you need to consider how long it takes 0.7uA to discharge a 10pF capacitance.
 
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