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| How can a chip (HX711) work without a ground pin connected? |
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| free_electron:
--- Quote from: SiliconWizard on June 14, 2018, 05:11:10 pm --- --- Quote from: Tonn on June 14, 2018, 03:48:06 pm ---A clamping diode on the RATE input pin, or similar, would explain this. --- End quote --- Except in very specific cases, IC pads usually have internal clamping diodes, so yes. --- Quote from: Tonn on June 14, 2018, 03:48:06 pm ---Could that be it? The chip being powered through an internal protection diode? And no one ever noticed this obvious design flaw? --- End quote --- Unless people connect E- to GND externally, in which case it would work properly. But the schematic would let you believe that you shouldn't. |O So yes, I think you're correct. As said in my post above, if you weren't correct, a chip without ground (or otherwise return path for the power supply) connection? That would seem to defy electronics laws. Wouldn't it? :popcorn: --- End quote --- not necessarily. 'ground' is just a reference ... just like 'power' you could make a chip that refers everything to VCC ... in fact, that has been done. Many POTS (Plain Old Telephone System) SLICs (Subscrier Line Interface Circuit ) work that way , simply because POTS uses negative voltages. The chip is powered with 'ground' and -48 volts. 'ground' is the positive terminal. All signal are referred to that 'ground'. to bring out the control signals you use level shifters using two transistors to a positive voltage 'above' ground. modern slics have those built in. |
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