Because the Arduino (and Basic Stamp) are 5V devices, and most modern sensors, displays, flash cards and modes are 3.3V-only, many makers find that they need to perform level shifting/conversion to protect the 3.3V device from 5V.We do have some other handy level shifters in the shop, from the DIP 74LVC245 to the fancy bi-directional TXB0108. However, neither of these are happy to work with I2C, which uses a funky pull-up system to transfer data back and forth. This level shifter board combines the ease-of-use of the bi-directional TXB0108 with an I2C-compatible FET design following NXP's app note.This breakout has 4 BSS138 FETs with 10K pullups. It works down to 1.8V on the low side, and up to 10V on the high side. The 10K's do make the interface a little more sluggish than using a TXB0108 or 74LVC245 so we suggest checking those out if you need high-speed transfer.While we designed it for use with I2C, this works as well for  TTL Serial,  slow <2MHz SPI, and any other digital interface both uni-directional and bidirectional. Comes with a fully assembled, and tested PCB with 4 full bidirectional converter lines as well as 2 pieces of 6-pin header you can solder on to plug into a breadboard or perfboard.

Because the Arduino (and Basic Stamp) are 5V devices, and most modern sensors, displays, flash cards and modes are 3.3V-only, many makers find that they need to perform level shifting/conversion to protect the 3.3V device from 5V.Although one can use resistors to make a divider, for high speed transfers, the resistors can add a lot of slew and cause havoc that is tough to debug. For that reason, we like using 4050/74LVX245 series and similar logic to perform proper level shifting. Only problem is that they are only good in one direction which can be a problem for some specialty bi-diectional interfaces and also makes wiring a little hairy.That's where this lovely chip, the TXB0108 bi-directional level converter comes in! This chip perform bidirectional level shifting from pretty much any voltage to any voltage and will auto-detect the direction. Only thing that doesn't work well with this chip is i2c (because it uses strong pullups which confuse auto-direction sensor). If you need to use pullups, you can but they should be at least 50K ohm - the ones internal to AVRs/Arduino are about 100K ohm so those are OK! Its a little more luxurious than a 74LVX245 but if you just don't want to worry about directional pins this is a life saver!Since this chip is a special bi-directional level shifter it does not have strong output pins that can drive LEDs or long cables, it's meant to sit on a breadboard between two logic chips! If you do not need instant bi-directional support, we suggest the 74LVX245 as below which has strong output drive.This breakout saves you from having to solder the very fine pitch packages that this chip comes with. We also add 0.1uF caps onto both sides and a 10K pull-up resistor on the output enable pin so you can use it right out of the box!

This tiny logic level shifter features four bi-directional channels, allowing for safe and easy communication between devices operating at different logic levels. It can convert signals as low as 1.5 V to as high as 18 V and vice versa, and its four channels are enough to support most common bidirectional and unidirectional digital interfaces, including I²C, SPI, and asynchronous TTL serial.

As digital devices get smaller and faster, once ubiquitous 5 V logic has given way to ever lower-voltage standards like 3.3 V, 2.5 V, and even 1.8 V, leading to an ecosystem of components that need a little help talking to each other. For example, a 5 V part might fail to read a 3.3 V signal as high, and a 3.3 V part might be damaged by a 5 V signal. This level shifter solves these problems by offering bidirectional voltage translation of up to four independent signals, converting between logic levels as low as 1.5 V on the lower-voltage side and as high as 18 V on the higher-voltage side, and its compact size and breadboard-compatible pin spacing make it easy to integrate into projects.

The logic high levels on each side of the shifter are achieved by 10 kΩ pull-up resistors to their respective supplies; these provide quick enough rise times to allow decent conversion of fast mode (400 kHz) I²C signals or other similarly fast digital interfaces (e.g. SPI or asynchronous TTL serial). External pull-ups can be added to speed up the rise time further at the expense of higher current draw. See the schematic diagram below for more information.

Dual-supply bus translation:

Lower-voltage (LV) supply can be 1.5 V to 7 V

Higher-voltage (HV) supply can be LV to 18 V

Lower-voltage (LV) supply can be 1.5 V to 7 V

Higher-voltage (HV) supply can be LV to 18 V

Four bidirectional channels

Small size: 0.4″ × 0.5″ × 0.08″ (13 mm × 10 mm × 2 mm)

Breadboard-compatible pin spacing

Example wiring diagram for connecting 5 V and 3.3 V devices through the 4-channel bidirectional logic level shifter.

This logic level converter requires two supply voltages: the lower-voltage logic supply (1.5 V to 7 V) connects to the LV pin and the higher-voltage supply (LV to 18 V) connects to the HV pin. The HV supply must be higher than the LV supply for proper operation. Logic low voltages will pass directly from Hx to the corresponding Lx (and vice versa), while logic high voltages will be converted between the HV level to the LV level as the signal passes from Hx to Lx or Lx to Hx.

The level shifter circuit does not require a ground connection to either device, so there are no ground pins on the board. (Some competing level shifter modules provide ground connections that simply act as a pass-through; we have opted to leave these off and make the board smaller.) The two devices being connected through the level shifter must still share a common ground.

The picture below shows a level-shifted TTL serial connection (RX and TX) between a 5 V Arduino Uno and a 3.3 V Raspberry Pi.

Using the 4-channel bidirectional logic level shifter to create a serial connection between a 5 V Arduino Uno and a 3.3 V Raspberry Pi.

A 0.1″-pitch male header strip is included for use with this board. The strip can be broken into smaller pieces and soldered in so the board can be used with perfboards, breadboards, or 0.1″ female connectors. Alternatively, wires can be soldered directly to the board for more compact installations. The connections are labeled on the back side of the of the PCB, so you might find it more convenient to solder the pins in the way that allows the labeled side to be facing up.

Schematic diagram

The logic level conversion is accomplished with a simple circuit consisting of a single n-channel MOSFET and a pair of 10 kΩ pull-up resistors for each channel. When Lx is driven low, the MOSFET turns on and the zero passes through to Hx. When Hx is driven low, Lx is also driven low through the MOSFET’s body diode, at which point the MOSFET turns on. In all other cases, both Lx and Hx are pulled high to their respective logic supply voltages. External pull-ups can be added to speed up the rise time. This same circuit is detailed in NXP’s application note on I²C bus level-shifting techniques, and we have used it before on carrier boards for 3.3 V sensors with I²C interfaces – like the MinIMU-9 – to enable them to work directly with both 3.3 V and 5 V systems.

This schematic is also available as a downloadable PDF (135k pdf).

People often buy this product together with:

If you’ve ever tried to connect a 3.3V device to a 5V system, you know what a challenge it can be. The SparkFun bi-directional logic level converter is a small device that safely steps down 5V signals to 3.3V AND steps up 3.3V to 5V at the same time. This level converter also works with 2.8V and 1.8V devices. What really separates this Logic level converter from our previous versions is that you can successfully set your high and low voltages and step up and down between them safely on the same channel. Each level converter has the capability of converting 4 pins on the high side to 4 pins on the low side with two inputs and two outputs provided for each side.

The level converter is very easy to use. The board needs to be powered from the two voltages sources (high voltage and low voltage) that your system is using. High voltage (5V for example) to the ‘HV’ pin, low voltage (3.3V for example) to ‘LV’, and ground from the system to the ‘GND’ pin.

Get Started with the Logic Level Converter Guide

Features

0.63 x 0.52" (16.05 x 13.33mm)