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By Alli
I have recently purchased your BME280 breakout board and i read on your website that the I2C pins have a 5V tolerance. I did not see mention of the supply pins being 5V tolerant. i would like to know if the board has an internal 3.3V regulator connected to the supply pins i.e. can i connect a 5V supply to the input pins of this breakout board?
By paulvha
The BME280 datasheet shows that the operating voltage is 1.7/1.2 to 3.6V.
According to the schematics, there is no regulator on the board so you have to provide 3v3.
By jremington
The Sparkfun claim on the product page that the BME280 inputs are "5V tolerant" is wrong. I've emailed support and asked them to fix this.

The BME280 data sheet clearly states that Vddio must be less than 3.6V, and that the pin input voltage must NOT exceed Vddio+0.3V.

Use this device only with 3.3V MCUs, or with 3.3V to 5V level shifters. Study the hookup guide, which has the correct information about using 3.3V MCUs. ... -guide/all
By jremington
Tech support responded to my email thusly:
Thanks for reaching out but I am not sure I see the error you are mentioning. The description explicitly states this board has a 3.3V-tolerant SPI interface and a 5V-tolerant I2C interface. Both of those are correct as the breakout has pull-up resistors to 3.3V/Vcc so it can work with higher voltage systems so long as the input voltage is 3.3V. The Vin/Vcc inputs on this breakout are clearly labeled for 3.3V only and the Operation Voltage is listed at 3.3V as well. The user you are mentioning most likely connected the 3.3V pins to 5V, resulting in the damage to the sensor.
The tech support person obviously does not understand the meaning of the phrase "5V-tolerant interface", which means that 5V can be applied to the interface inputs without damage to the device. That is not the case for the BME280 module in question.

Where does Sparkfun find these incompetent employees?

The fact is, many 5V microprocessor boards, including certain Arduinos, have pullups to 5V on the I2C lines. Those pullups cannot be disabled without hardware modifications. Connecting such microprocessor boards to 3.3V I2C devices can cause them to malfunction or even destroy them.
User avatar
By TS-Chris
Woah, hold on just a minute. No need for name calling!

I can't find any documentation specifically saying that the I2C interface is in fact 5 volt tolerant, but it's very possible that the designer of the board had information at the time the board was designed that said otherwise. This doesn't mean the description is wrong, it just means I can't find anything that proves it's right. It's quite possible there is an addendum or or document from Bosch somewhere that prompted the engineer that made the board to include that in the description. It's also possible someone made a mistake, but that doesn't make them incompetent.

Because I can't find solid documentation supporting 5 volt tolerance for I2C, I'm requesting that our catalog team remove that from the description. If we're able to track down evidence that it's safe to use these on a 5 volt I2C bus, we will post that along with the data sheet.