Bi-Directional MOSFET Voltage Level Converter 3.3V to 5V

Bi-Directional MOSFET Voltage Level Converter 3.3V to 5V

When connecting 3.3V devices and 5V devices voltage level conversion is required. The following circuit will allow this to be done bi-directionally

MOSFET Level Converter

Low Side Control

When the low side (3.3V) device transmits a '1' (3.3V), the MOSFET is tied high (off), and the high side sees 5V through the R2 pull-up resistor. When the low side transmits a '0' (0V), the MOSFET source pin is grounded and the MOSFET is switched on and the high side is pulled down to 0V.

High Side Control

When the high side transmits a '0' (0V) the MOSFET substrate diode conducts pulling the lowside down to approx 0.7V, this is also low enough to turn the MOSFET on, further pulling the low side down. When the high side transmits a '1' (5V) the MOSFET source pin is pulled up to 3.3V and the MOSFET is OFF.

Note This works with I2C and other open collector type gates

No 3.3V Supply?

If you dont have access to the 3.3V supply (maybe the 3.3V voltage regulator is on a breakout board) you can simply tie the gate to 3.3V via a simple voltage divider as in the diagram below

mosfet level converter no 3.3v

2N7000 MOSFET product page

You may also be interested in our Logic Level Converter board

See also the tutorial on Schottky Diode Logice Level Conversion

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