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| Pull Down resistor |
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| Nikos A.:
Hi everyone, I design a circuit that will support 8 analog sensors and the MCU will read each analog value through a multiplexer. After debugging the circuit I realized that the empty header sockets (no sensors connected) are actually floating inputs... I am thinking of placing a pull-down resistor on each of the multiplexer inputs (15 in total) to avoid this situation. Is there a better solution instead of placing fifteen pull-down resistors? This is the initial circuit. |
| David Hess:
That depends on the application and on how the multiplexer is constructed but in general, unused inputs should be tied to some potential within the supply range. Otherwise current injected into the substrate through the unused input can cause error in other channels. If impedances and accuracy requirements are low, then this may not be an issue. Multiplexers built on dielectrically isolated processes may not suffer from this. |
| Nikos A.:
--- Quote from: David Hess on December 27, 2019, 03:17:59 pm ---That depends on the application and on how the multiplexer is constructed but in general, unused inputs should be tied to some potential within the supply range. --- End quote --- Thank you for your answer. I will tie the pins to the ground but I was wondering if there is any better solution besides connecting a single pull-down resistor to each of the MUX io pins. |
| GeorgeOfTheJungle:
The signals TEMP and HUM are digital or analog? |
| Wimberleytech:
Why not use a single pull down resistor on the downstream side of the mux? |
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