A customer has set his pull-up on the A side SDA line to 6.5k and still the I2CVol is at 800mV. Any suggestions on how to get this lower? If I understand it correctly, when 410mV < sideA < 800mV that means that Side B is driving and Side A is responding. Customer would like to be closer to the 410mV level.
Just a quick note - we can see from table 2 in the Si860x Datasheet that the output low level for side A is going to be between 540mV and 800mV.
The 410mV you have listed there is actually the threshold when side A is being used at an input.
Let me see what else we can do:
Are you using the device at room temp?
What is the bus voltage you're operating at?
Another quick suggestion - If the tolerance on the B-side is better, flip the part around!
Due to the anti-latch circuitry on the isolator's A-Side, the Vol (output low) is higher on the A-side then it is on the B-side, per Table 3.