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I am trying to understand the meaning of a 3.3v or 5v IC but I don't know how to use the right keyword in search engine to find the explaining article so I'll explain...

We know Arduino UNO R3 as example have 5v and 3.3v power out pins so I could use to to supply the Sensors or other components in circuit but sometime I read "this sensor is 5v only" or "3.3v only", what does that mean? Does that mean you should power the sensor with five volt or the 5 volt for IO pins of sensor and if the sensor 3.3v does that mean this value for IO pins of data like 3.3v that means Logic 1 and if 0V that's mean Logic 0 and the same things for 5V.

I read Arduino Mega difference than Arduino Duo because Duo is 3.3v only, I hope to fine some explaination of how to solve problem like this if we want to run 3.3v sensor on 5V MCU or 5V sensor on 3.3V MCU . Do I need level shifting ?

Second question Seeedstudio say their sensor "Grove - IMU 9DOF v2.0" is Working Voltage: 5V

http://www.seeedstudio.com/depot/Grove-IMU-9DOF-v20-p-2400.html?cPath=25_134

the schematic for board design

https://www.docdroid.net/qRsbWXl/grove-imu-9dof-v20.pdf.html

show use of 5V to 3.3v voltage regulator for input of chip while the chip used is InvenSense MPU-9250 when I check the Voltage - Supply for Chip in Digi key I found it 2.4 V ~ 3.6 V, can someone explain if that this 3.3v for IO pins for data because it use I2C as data bus or what?

Thanks for everyone shearing his knowledge in this site,

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    \$\begingroup\$ I didn't know that zero punctuation frequents electronics.se. I tried to understand what your question is, but couldn't decipher what you meant. \$\endgroup\$
    – jms
    Feb 10 '16 at 16:58
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    \$\begingroup\$ Your question, as it stands, is really hard to understand. Yet the question subject is particularly simple. I would say you are overcomplicating your thoughts. \$\endgroup\$ Feb 10 '16 at 17:01
  • \$\begingroup\$ what is complex part in my question, let me simplify it, how much the voltage value that pass through the IO pins for I2C buss in Grove - IMU 9DOF v2.0, \$\endgroup\$
    – Haider
    Feb 10 '16 at 17:05
  • \$\begingroup\$ if this not clear, why they say 5V sensor and then use 3.3v voltage regulator in the design of sensor, you could check the scheme? \$\endgroup\$
    – Haider
    Feb 10 '16 at 17:06
  • \$\begingroup\$ Short answer: for end-user confort =) they know most hobbysts like to use arduino and 5V logic levels, so they are taking a 3v3 chip and plugging on a pcb with a logic level converter. So that you don't have to trouble doing it yourself. \$\endgroup\$ Feb 10 '16 at 17:10
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Typically, an IC's input and output logic is tied to the IC's power. A 5V IC will typically have GPIO that are 0 to 0.2 * VCC for logic Low, and 0.6~0.7 * VCC to VCC + 0.3V for logic High. This can vary, but its a good rule of thumb.

Sometimes you will see a 3.3V IC module have it's own regulator, and it expects 5V, to the module, but it will either expect 3.3V logic, or need/provide a logic-level translator.

The Module you ask about is the second type. It has it's own 3.3V regulator. It also provides logic level translation, using a pair of mosfets on the i2c lines, allowing you to connect a 5V i2c signal to it's 3.3V i2c signal.

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  • \$\begingroup\$ thanks for answer, I understand the usage of Logic level from Vicente Cunha reply, and your answer complete the other part of explain with more details, instead of asking another question in this site could you tell me you they use chip that have 3 pins which called mosfets in "Grove - IMU 9DOF v2.0" in know in that sensor work with 3.3v and it's use i2C and i2c need pull up or down resister whatever.. so that is that chip and why use it in the circuit,and in the schematic from their location in circuit what you understand the purpose of it. \$\endgroup\$
    – Haider
    Feb 10 '16 at 17:23
  • \$\begingroup\$ I know this is another question but I search in this site about use of mosfets in Arduino board or other circuit but didn't what I want. \$\endgroup\$
    – Haider
    Feb 10 '16 at 17:27
  • \$\begingroup\$ @Haider i honestly can't understand what you are trying to ask. \$\endgroup\$
    – Passerby
    Feb 10 '16 at 18:29
  • \$\begingroup\$ Why use mosfets in "Grove - IMU 9DOF v2.0" as show in schematic, does we need mosffet when we design logic level translation? \$\endgroup\$
    – Haider
    Feb 10 '16 at 19:00
  • \$\begingroup\$ @Haider mosfets are used, as they are a convenient method. Doesn't mean they are the best, honestly probably just the cheapest. There are ICs that do level translation much better. \$\endgroup\$
    – Passerby
    Feb 10 '16 at 19:03

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