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DS90UB947-Q1: I2C level

Roy Chou1
Genius 16055 points
Part Number: DS90UB947-Q1

Hi team,

I find the pin13 description in datasheet. 

I2C Voltage Level Strap Option Tie to VDDIO with a 10-kΩ resistor for 1.8-V I2C operation. Leave floating for 3.3-V I2C operation. This pin is read as an input at power up.

Does it mean that I2C level is follow this pin instead of VDDIO level? And could you let us know the how 947 boost the voltage from 1.8 to 3.3V?

If we use 1.8V I2C level but connect to MCU which is 3.3V I2C level, does it have any risk?

Roy

  • 0
    TI__Mastermind 25955 points

    Hi Roy,

    Pin 13, I2CSEL is a strapped input to the 947.  On powerup of the device this pin is measured, and if  it is set to 1.8 V as described in the datasheet, I2C will operate with 1.8 V logic thresholds.

    If I2CSEL is left floating, I2C will operate with 3.3 V logic thresholds.

    I2C utilizes open-drain drivers.  The SDA and SCL pins are tolerant to 3.3V  If I2CSEL is set for 1.8 V operation, ensure that the SDA and SCL pins are pulled up externally to a 1.8V rail.  If I2CSEL is set for 3.3 V operation, ensure that the SDA and SCL pins are pulled up externally to a 3.3 V rail.

    When using 3.3 V I2C, in general, it is recommended to use VDDIO = 3.3 V.

    Sincerely,
    Bryan Kahler

  • 0 in reply to Bryan Kahler
    TI__Genius 16055 points

    Hi Bryan,

    But the 947 could only use 1.8V VDDIO.

    If our MCU use 3.3V I2C to give the command, does it mean that we set the I2CSEL left floating to let I2C operate with 3.3 V logic thresholds.

    Is it right?

    Roy

  • 0 in reply to Roy Chou1
    TI__Mastermind 25955 points

    Hi Roy,

    Yes, with the 948 VDDIO can be either 1.8 V or 3.3 V.

    For 3.3 V I2C operation with the 947, leave I2CSEL floating for 3.3 V logic thresholds.

    Ensure SDA and SCL are pulled up to 3.3 V.

    Sincerely,
    Bryan Kahler