TUSB1104 datasheet(44/55 Pages) TI

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11.1 USB SSTX1/2 Receiver Configuration

Configuring the TUSB1104 involves understanding the insertion loss (SDD21) of the pre-channel (XAB). The

TUSB1104's SSEQ[1:0] pins if pin-strap mode, or if I2C mode, SSEQ2_SEL and SSEQ1_SEL registers should

be set to the level of the pre-channel insertion loss at 5 GHz. A good rule for FR4 trace insertion loss at 5 GHz

is ≈-1 dB per inch. Using this rule, if the pre-channel for USB (XAB) is 8-inches, the TUSB1104 SSEQ should be

programmed to -8 dB.

11.2 USB CRX1/2 Receiver Configuration

11.2.1 Fixed Equalization

In Fixed EQ operation, a single EQ setting is used for all possible devices inserted into the USB receptacle (with

or without USB cable). It is recommended to set TUSB1104 CEQ[1:0] pins if pin-strap mode, or CEQ1_SEL

and CEQ2_SEL if I2C mode to about 4 db to 5 dB greater than loss of the post channel (XCD). For example,

if post channel is 0.5 inches, then assuming -1 dB per inch at 5 GHz, CEQ1_SEL and CEQ2_SEL should be

programmed to 4.5 to 5.5 dB. It is recommended to perform USB 3.1 Rx JTOL long and short channel tests to

optimize the setting. Depending of the USB 3.2 Host, a single EQ setting which satisfies both the long and short

channel tests may not be possible. If this is the case, then it is recommended to use AEQ mode.

11.2.2 Full Adaptive Equalization

In Full AEQ mode, the TUSB1104 will determine the best settings regardless if the channel is short, long or

somewhere in between. In pin-strap mode, the Full AEQ is enabled based on the state of AEQENZ pin. In I2C

mode, the Full AEQ feature is enabled by default. Full AEQ is enabled when AEQ_MODE = 1, 2, or 3, and

AEQ_EN = 0x1.

11.2.3 Fast Adaptive Equalization

Fast Adaptive EQ will distinguish between a short and long channel and select a pre-determined EQ setting

based on which channel is detected. Fast AEQ is available only I2C mode. Fast AEQ is enabled when

AEQ_MODE = 0 and AEQ_EN = 1.

The EQ setting used for short channel should be programmed into CEQ1_SEL and CEQ2_SEL registers. It is

recommended to program these registers about 1 dB to 2 dB more than the loss of post channel (XCD). For

example, if post channel is 0.5 inches, then assuming -1dB insertion loss per inch at 5 GHz, CEQ1_SEL and

CEQ2_SEL should be programmed to 1.5 to 2.5 dB. It is recommended to perform USB 3.2 Rx JTOL Short

channel test to find the optimal short channel setting.

The EQ setting used for long channel should be programmed into LONG_CEQ1 and LONG_CEQ2. It is

recommended to program these registers about 4 to 5 dB more than the loss of post channel (XCD). For

example, if post channel is 0.5 inches, then assuming -1 dB per inch at 5 GHz, LONG_CEQ1 and LONG_CEQ2

should be programmed to 4.5 to 5.5 dB. It is recommended to perform USB 3.2 Rx JTOL Long channel test to

find the optimal long channel setting.

TUSB1104

SLLSFL1 – APRIL 2022

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