Timeline for I2C level shifter isolation
Current License: CC BY-SA 4.0
12 events
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| Jan 25 at 10:24 | comment | added | Justme | @electroeso Depends on the situation. My concern is, your simulation showed about 3V on the 1V8 side too. Perhaps you are not simulating it properly. If you assume FET has tiny amount of capacitance between the pins, and 1V8 supply is floating, there will be nearly 0V over the FET pins as there is nothing to charge or discharge it, and thus both sides are nearly are at same voltage, and as one side is at 3.3V then other side is at 0V too. If VCCIO is 0V then it's 0V, not floating. | |
| Jan 25 at 10:04 | comment | added | electroeso | Oh @Justme, you confused my mind 😅. I have never found any spice model for FXMAR2102. My purpose was to verify this in the simulation and then go forward. But couldn't do it. What do you prefer? Do you think I should proceed with the simple solution that I verified with Spice simulation or with a part that looks good on the datasheet? | |
| Jan 25 at 9:31 | comment | added | Justme | @electroeso Just be careful with that FXMAR2102 chip. They look good on paper and people put them on their design. Similar bi-dir auto-directional buffers are made by TI as well, and most questions here about them is why they don't work as expected, but the expectations are genrally unrealistic and the chip is used in an environment it cannot work properly. There are less smart I2C level shifting solutions that may work better because they are simpler. | |
| Jan 25 at 8:04 | history | edited | ocrdu | CC BY-SA 4.0 |
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| Jan 25 at 1:59 | comment | added | electroeso | Oh come on, how did I miss this? I did a lot of research beforehand, I remember seeing something similar. But it made sense to try the discrete solution to push the 400p capacitance limit and for cheap isolation (discrete resistors were needed anyway, I didn't want to add an enable resistor and VCC line capacitors). However, this device seems to give exactly the effect I want in terms of isolation. Engineering time is always important, but maybe it was a little wasted this time, okay :)) Thank you very much for the suggestion. I will try this. | |
| Jan 25 at 0:50 | comment | added | ElectronicsStudent | Check Fairchilds FXMAR2102 - 1.2x1.4mm, 0.16€/pc @5kPcs, Output-Enable (Can be Handy) and no passives (If layout is done correct) required. Will neither be cheaper, nor simpler, nor more reliable with a discrete solution. Also think about your engineering time. | |
| Jan 24 at 22:10 | comment | added | electroeso | Yes, I know. However, this solution is more logical for size, cost, and external component usage cases. I have already investigated dedicated level shifters and then made decisions this way. | |
| Jan 24 at 18:29 | comment | added | ElectronicsStudent | There are dedicated ICs for these applications. Cheap, simple, realiable. See DigiKey/Mouser ... etc | |
| Jan 24 at 18:24 | answer | added | kaosad | timeline score: 1 | |
| Jan 24 at 12:26 | review | Close votes | |||
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| Jan 24 at 10:28 | history | edited | electroeso | CC BY-SA 4.0 |
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| Jan 24 at 10:26 | history | asked | electroeso | CC BY-SA 4.0 |