๐งฑ Current Thresholds
In digital electronics, current thresholds define how much electrical current a device can source, sink, or tolerate at its input or output pins. While voltage thresholds determine signal interpretation, current thresholds govern physical drive strength and loading limits.
Setting Boundaries
To ensure safe and reliable operation, we define current thresholds for input and output pins:
How much current an output can safely source or sink
How much current an input can safely draw or leak
๐งญ Naming Convention
Each label follows the format:
$I_{XY} (B)$
Where:
$I$ = Current
$X$ = Signal type I = Input O = Output
$Y$ = Direction H = Source (current flows out) L = Sink (current flows in)
$B$ = Bound type
max = Maximum safe current
min = Minimum guaranteed current (rarely used)
โ๏ธ Table of Current Thresholds
These thresholds define how much current a digital device can handle or deliver at its pins. They are critical for ensuring that outputs can drive loads and inputs are not overloaded.
| Threshold | Interpretation Logic |
|---|---|
| $I_{IL}$ (max) | Maximum current allowed into input when LOW voltage is applied |
| $I_{IH}$ (max) | Maximum current allowed into input when HIGH voltage is applied |
| $I_{OL}$ (max) | Maximum current the output can sink while maintaining LOW voltage |
| $I_{OH}$ (max) | Maximum current the output can source while maintaining HIGH voltage |
These thresholds define electrical stress limits, not logic levels. Exceeding them can cause voltage droop, signal distortion, or permanent damage.
๐ง What Do โSourceโ and โSinkโ Mean?
| Direction | Current Flow | Typical Role |
|---|---|---|
| Source | Current flows out of the pin | Output driving HIGH |
| Sink | Current flows into the pin | Output pulling LOW or input loading |
- Output HIGH โ sources current to downstream load
- Output LOW โ sinks current from downstream load
- Input pins โ draw small leakage or bias currents depending on voltage level