MLX90640 I2C @ 5V or 3.3V at I2C fast mode plus

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karelv
 
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MLX90640 I2C @ 5V or 3.3V at I2C fast mode plus

Post by karelv »

Hello folks!

For this product: https://www.adafruit.com/product/4407
It is stated that it works in a range from 3V to 5V.
Now, I am wondering, as for the datasheet of mlx90640, it says it works from 3.0 to 3.6 Volts.
This includes the levels on the I2C lines.
At the adafruit product page I could not find the schematic, but I suppose there must be level shifters for the SDA&SCL lines.
My question is two folded:
1] is there a levelshifter on this board for I2C?
2] if there is, does that level shifter has impact on the max allowed I2C frequency? (datasheet allow up to 1MHz; FM+)
Thanks,
K.

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adafruit_support_bill
 
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Re: MLX90640 I2C @ 5V or 3.3V at I2C fast mode plus

Post by adafruit_support_bill »

Schematics can be found on the Downloads page of the guide: https://learn.adafruit.com/adafruit-mlx ... /downloads

There is a 3.3v regulator on the board. So the MLX906040 is running at 3.3v. There are BSS138 level shifters for the signal lines. These should handle a 1MHz clock.

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karelv
 
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Re: MLX90640 I2C @ 5V or 3.3V at I2C fast mode plus

Post by karelv »

Hello Bill,

Thanks for your quick reply.

I ordered, so I will know soon!
Meanwhile I was reviewing the datasheet (https://melexis.com/mlx90640)
datasheet snippet
datasheet snippet
2023-01-13 09_44_44-MLX90640-Datasheet-Melexis.pdf - Adobe Acrobat Reader DC (32-bit).png (110.14 KiB) Viewed 89 times
And it seems there are no level shifters needed. Can you comment on why you added the level shifters?

Thanks,
K.

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Re: MLX90640 I2C @ 5V or 3.3V at I2C fast mode plus

Post by adafruit_support_bill »

We work with devices from many sources and every manufacturer has a different idea of how to organize a data sheet. But signal levels and limits are most commonly specified in an "Electrical Specifications" table. I suspect that the designer was working from the General Electrical Specifications in section 8. There is no maximum signal voltage listed there. And the general rule is not to exceed Vdd.

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