SDA pull down in PF4210 & PF0100

[wswong]

Dear Team,

Customer found SDA pin of PMIC PF4210 keep in low status when VDDIO is supplied (VDDIO =3.3V) but without VIN (VIN = 0V). There is no such issue in SCL pin and it can pull up with VDDIO only. Both SCL and SDA pin are pull up to VDDIO with 4.7K resistors. If VIN is supplied (3.3V), the SDA status can pull up to VDDIO level and that status can keep  even after VIN is turn off. Same result can be found in both PF4210 EVK and customer board.    

That issue affect other slave devices on the same I2C bus cannot be communicate if supply does not provide to PMIC VIN.   

Similar symptom can also be measured in PF0100 EVB. Is that symptom normal?  Does VIN must power for the I2C interface/SDA level stable setup to open-drain pull up?

For the application that other slave devices need share the I2C interface/bus with the PMIC (but no need PMIC to work), customer try workaround by power up VIN once, then power it down and only keep VDDIO supply. Is that workaround reliable and What is the suitable workaround for that issue case?  

Can we share the internal block diagram of the I2C interface of PMIC to explain that symptom.   

Thanks and Best Regards,

WS

[jinyuzhang · Accepted solution]

Hi Ws

    I have checked on EVB , and the result is the same to you. this is not a good symptom, but we can't regard it as a bug. as when there is no VIn ,Vdig has no output and there is no voltage to control the internal MOS, most of circuit is Floating status, and then if there is a pull up for SDA , the Open Drain mos of SDA may be turned on. I test the leakage current , it is about 600uA, and it seems like the MOS is turned on.

    The thing we can do just recommend customer to keep VIN on when VDDIO is on,

BRs

jinyu

[wswong]

Hi Jinyu,

Thanks for your update and we can recommend customer to keep VIN on.

Is there any internal block/circuit diagram can help us descript that operation?

Thanks and Best Regards,

WS

[jinyuzhang]

Hi Ws

     I have no access to look through the internal circuit, anandkumarbalakrishnan‌, do you have any idea about this "issue"?

BRs

jinyu