January 6, 2008
about 3 years ago
Member #34624 is right on. The operation of this circuit has nothing to do with a voltage divider to maintain the voltages.
It has to do with the gate on the MOSFET being held at 3.3V, so that current will only flow to “top up” the voltage in the low side if the voltage on the low side is anything less than 3.3V. With some small leakage to ground the voltage on the low side will stay at 3.3 unless the I2C device pulls that side to ground (transmit from I2C device), or the voltage on the high side falls to ground (transmit from microcontroller).
I’ve made my own version of these, but heck, these are cheap enough and look prettier than what I can make, so I’ll get some.
No public wish lists :(
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