SLLSFZ7 February 2025 TUSB1146-Q1
PRODUCTION DATA
The Fast AEQ mode is used to distinguish two channels (short channel and a long channel) and choose the appropriate receiver equalization setting for that channel. Fast AEQ only distinguishes between two choices, therefore the AEQ time is a lot shorter than Full AEQ mode, which minimizes impact to USB link training.
When Fast AEQ is enabled and channel is determined to be short, the TUSB1146-Q1 uses the value programmed into the EQx_SEL, where x = 1 or 2. If the TUSB1146-Q1 determines channel is not short, the TUSB1146-Q1 switches to the EQ value programmed into the LONG_EQx register, where x = 1 or 2. During initial system evaluation, TI recommends to perform both short and long channel USB3.2 RX JTOL testing and program EQx_SEL and LONG_EQx to the value which produced the best results for each channel configuration.
The TUSB1146-Q1 determines short and long based on the estimate eye height. The value programmed into FASTAEQ_LIMITS register determine the eye height limits. Software can change the defaults of this register to lower or raise the limits.
EQ_OVERRIDE field must be set for values programmed into EQx_SEL and LONG_EQx to be used.
TI recommends to change the FASTAEQ_LIMITS register from the default value to 0x2 (80mV).