The datasheet of TI bq40z50-R2 (Li-Ion Battery Pack Manager) tells that "The SMBus clock and data lines have internal pulldown".
Pin equivalent Diagram is in image below:
Aren't usually the SMBus Data and Clock lines to be connected to pull-up resistors?
I'd like to connect this IC and a Battery Charger IC to same SMBus, but the latter requires pull-up resistors for the SMBus lines.
Would this work anyway?
Thanks
Best Answer
The internal pull-downs in question are very weak, 1 MΩ. They are not meant to be "operational", and won't have any effect on normal I2C data transactions when the standard (10k-5k or 2k) pull-ups are attached to the I2C system bus. The reason for weak pull-downs is to provide well-defined bus state during power-on transients, when not all parts of the system are yet powered up.
The initial state with pull-downs is used by internal logic of the IC, per datasheet P.34: