Logic Levels

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3.3 V CMOS Logic Levels

As technology has advanced, we have created devices that require lower power consumption and run off a lower base voltage (Vcc = 3.3 V instead of 5 V). The fabrication technique is also a bit different for 3.3 V devices that allows a smaller footprint and lower overall system costs.

3.3V Logic Level Tolerances

In order to ensure general compatibility, you will notice that most of the voltage levels are almost all the same as 5 V devices. A 3.3 V device can interface with a 5V device without any additional components. For example, a logic 1 (HIGH) from a 3.3 V device will be at least 2.4 V. This will still be interpreted as a logic 1 (HIGH) to a 5V system because it is above the VIH of 2 V.

A word of caution, however, is when going the other direction and interfacing from a 5 V to a 3.3 V device to ensure that the 3.3 V device is 5 V tolerant. The specification you are interested in is the maximum input voltage. On certain 3.3 V devices, any voltages above 3.6 V will cause permanent damage to the chip. You can use a simple voltage divider (like a 1KΩ and a 2KΩ) to knock down 5 V signals to 3.3 V levels or use one of our logic level shifters.

SparkFun Logic Level Converter - Bi-Directional

SparkFun Logic Level Converter - Bi-Directional

BOB-12009
$2.95
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SparkFun Opto-isolator Breakout

SparkFun Opto-isolator Breakout

BOB-09118
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SparkFun Voltage-Level Translator Breakout - TXB0104

SparkFun Voltage-Level Translator Breakout - TXB0104

BOB-11771
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SparkFun Level Translator Breakout - PCA9306

SparkFun Level Translator Breakout - PCA9306

BOB-15439
$3.95