I am using ST25DV04KC tag and using the V_EH pin to power the VCC of the tag only( It will generate around 3.3V which is enough to power up the tag in I2C mode I believe) . I am looking for guidance on the maximum pullup voltage on the I2C and GPO line from an external rail of around 3.6V, if it is okay? what can be the max voltage on the I2C and GPO pins? is it independent of VCC or dependent on VCC?
Hello,
The voltage put on pull-up resistors on the I2C pins and on the GPO pin can be different than the voltage on the VCC pin (I2C and GPO are true open drain pins). This is off course if you are using the open drain version of the GPO pin (ST25DV04K-IE, not -JF version).
The maximum voltage indicated in the maximum rating table in the datasheet (-0.5 to 6.5V) indicates the max that you can reach before damaging the device. Nevertheless, it is not recommended to operate the device at 6.5V.
The recommended operating values are described in the "I2C operating conditions" table and specifies that the voltage should be between 1.8 and 5.5V.
So, you can have a VCC of 3.3V and have pull-ups resistors on GPO and SCL/SDA between 3.3V and 5.5V (you can't go below VCC since the VIH min is 0.75xVCC).
Best regards.
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