5 DC_BOOST vs. RX Sensitivity (RX_SEN)

The TUSB216I has a 3-level RX_SEN setting (pin 9) to help recover signals in high loss environments. The mid RX_SEN setting is used in most applications with typical USB 2 signal amplitudes. Tuning this setting is recommended when the expected signal as seen at TUSB216I USB data pins amplitude is outside the normal range.

The recommendation is to start with mid RX_SEN setting and then move to high or low settings based on the signal amplitude as measured at the TUSB216I. For example, if the signal amplitude is low after the signal traverses a very long cable, use the high RX_SEN setting. For the TUSB216I to recognize any change to the RX_SEN setting, the RSTN pin must be toggled.

The TUSB212 has a 3-level DC_BOOST function on pin 9. Please note that the optimal DC_BOOST level on a TUSB212 implementation will not necessarily be the optimal RX_SEN setting for a TUSB216I implementation.

For both devices, pin 9 is sampled after Power-On Reset or de-assertion of the RSTN pin and becomes the ENA_HS status output afterwords. TI recommends to connect the ENA_HS signal to a test point on the PCB, so the output can be used for debug if needed.