TUSB216: What are the differences between I2C gain settings and hardware gain settings on the TUSB216?

Hi Jose,

Jose Lopez-Vergara said:

How are the gain's set by the chip? Is there a Lead/Lag compensator built into the IC to help provide the boost needed? 

There is no Lead/lap compensator. In GPIO mode the BOOST setting is determined by an internal comparator, while in I2C mode the BOOST is set via I2C registers.

Jose Lopez-Vergara said:

Would it be possible to further "Tune" the values to an inbetween stage, or do the resistances provided for the gain need to be within a certain tolerance around the values stated in the datasheet/on the EVM? (EX: Would Rboost set to 5.1K provide a boost level that would fall between boost levels 2 and 3?)

There are only the four listed levels available in GPIO mode. There is no way to set the level to an "in-between" level by using certain resistor values.

I2C mode allows for further tuning settings that would be between what is allowed in GPIO mode, as well as exceeding the max GPIO setting.

Jose Lopez-Vergara said:

Are there On-Die Resistors that the IC enables/disables by using I2C control?

No, the IC would not control on-die resistors with I2C. I2C would be purely software.

Jose Lopez-Vergara said:

How much do temperature swings affect the performance of the gain?

Temperature should have no effect on performance of the TUSB216 when boosting.

Jose Lopez-Vergara said:

Do we need to characterize the gain if the IC will live in an enclosure that stays around 40C nominally?

You should not need to characterize for 40C. The TUSB216 should perform as expected at this temperature.

Jose Lopez-Vergara said:

What happens when you have a high gain setting via hardware and then attempt to use the lower gain settings via I2C? Would it default to the highest gain? 

At start-up, the TUSB216 will monitor the BOOST and RX_SEN pins to see what the resistance and voltage levels of these pins are. 

If I2C PUs are present, then the TUSB216 can be placed into Configuration mode via register 0x03, where the BOOST and RX_SEN levels can be overwritten via I2C commands to register 0x01, 0x0E, and 0x25. After these values are written, the redriver can be set back to Normal mode, where the I2C writes should take effect.

Essentially, the redriver will default to the GPIO settings of the BOOST and RX_SEN pins, then can be adjusted retroactively if using I2C.

Thanks,

Ryan