How do I shift voltage levels?

Question

I want to use an RF12B to communicate over radio with an Arduino, but the transceiver is rated at 3.3 V. I hear I need to use a voltage level shifter, but what do these look like and where can I find a schematic to help me hook it up?

http://electronics.stackexchange.com/questions/708/i2c-3-3-to-5-0-v-conversion http://electronics.stackexchange.com/questions/622/bi-directional-step-up-and-step-down-3-3v-5-etc — Toby Jaffey, Jan 08 '11 at 14:24

stevenvh · Answer 1 · 2011-01-08T13:22:53.970

Microchip has this document with 19 tips about mixing 3V and 5V parts in a circuit (not just level shifting).
The tips:

Powering 3.3V Systems From 5V Using an LDO Regulator

Low-Cost Alternative Power System Using a Zener Diode

Lower Cost Alternative Power System Using 3 Rectifier Diodes

Powering 3.3V Systems From 5V Using Switching Regulators

3.3V → 5V Direct Connect

3.3V → 5V Using a MOSFET Translator

3.3V → 5V Using A Diode Offset

3.3V → 5V Using A Voltage Comparator

5V → 3.3V Direct Connect

5V → 3.3V With Diode Clamp

5V → 3.3V Active Clamp

5V → 3.3V Resistor Divider

3.3V → 5V Level Translators

3.3V → 5V Analog Gain Block

3.3V → 5V Analog Offset Block

5V → 3.3V Active Analog Attenuator

5V → 3V Analog Limiter

Driving Bipolar Transistors

Driving N-Channel MOSFET Transistors

score 3 · Answer 2 · edited Apr 13 '17 at 12:32

3

There's a couple of ways to to voltage level shifting, depending on how fancy you want to get. Just to name a single manufacturer, Texas Instruments has a whole section devoted to mixed-voltage interfacing between different protocols. You can almost guarantee that there's a chip that will fill your needs.

Alternatively, as pointed out in this answer, SparkFun makes a small board that will probably be the easiest solution to implement. Your radio appears to use SPI, which should be workable with that board.

edited Apr 13 '17 at 12:32

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answered Jan 08 '11 at 05:45

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The Texas Instruments link seems to be (effectively) broken. – Peter Mortensen Mar 28 '18 at 15:34

score 3 · Accepted Answer · edited Mar 28 '18 at 16:11

It depends what direction the signals are going to.

If the 5 V device is going to drive a signal on the 3.3 V device, use a simple resistor division.
If the 3.3 V device is going to drive a signal on the 5 V device, you could use two inverters with the last stage tied to 5 V. However, this requires four resistors and two transistors, which is quite an expense. You could also try out the implementation as shown in Sparkfun's breakbout board.
If the signal is bidirectional (I²C), maybe something in this appnote on page 10 will work (seems similar to what Sparkfun is using).

How do I shift voltage levels?

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