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Can the MMA8452 I2C Interface run at 1.8V while VDDIO is tied to 2.5V?

Question asked by Jake Wegman on May 6, 2014
Latest reply on May 7, 2014 by Jose Alberto Reyes Morales

Hello,

 

We've recently been informed that the MMA8450 has been marked for EOL, with the recommended replacement being the MMA8452.  The main difference between the two parts is that the MMA8452 uses a core voltage of 2.5V, whereas the MMA8450 could use a core voltage of 1.8V.  In our particular application, the MMA8450 was chosen because it meant that it could operate at the same I/O voltage as the microprocessor with which it was interfacing.  Also in the current design, the interrupt signals interface with some level shifting circuitry that then wake up the system in the event of a drop.  There is a separate regulator on the boards that operates at 1.8V to keep the MMA8450 alive while the rest of the system is powered down.  If the I2C interface on the MMA8452 can run at 1.8V while the rest of the sensor subsystem ran at 2.5V, then we would not have to change our board design; we could simply replace the 1.8V fixed regulator with the 2.5V equivalent.  According to the datasheet, the input voltage thresholds fall within range for a 1.8V system, but there are some notes in the datasheet about supply sequencing that make me think that this might not operate correctly if the I2C lines are using a different voltage than the rest of the chip.

 

Any insight is much appreciated; we have to make a decision on whether or not to respin the board quite soon.

 

Thanks,

Jake

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