TUSB1142: Initial EQ setting

Hi Roy,

I am assuming your system is like the block diagram below, please correct me if I am wrong:

Roy Chou1 said:

Can you tell us the difference between Table 6-2 / Table 6-3 and Table 6-6 / Table 6-7, which setting should we follow.

Table 6-2 shows the CRX EQ gain on the TUSB1142. This is the gain applied to signals coming from the Type-C connector. (Type-C --> 1142) You want this value to match the loss between the Type-C connector and the 1142. Since the length is less than 1in, you should start with a low value and work up as needed. An example starting value is EQ setting #1:

Table 6-3 shows the SSTX EQ gain on the TUSB1142. This is the gain applied to signals coming from the USB host. (USB Host --> 1142) You want this value to match the loss between the USB host and the 1142. Since you have 2.8dB loss from the B2B connection and <1in between the B2B and 1142, you could start with EQ setting #2. This would add 4.5dB gain to the TX signal from the host.

These two tables (6-2, 6-3) are only valid when the EQCFG pin is set to "0" or "F"

Tables 6-6 and 6-7 show the effect of changing the EQCFG pin to setting "1" or "R":

When you change EQCFG to "1/R" you can adjust the gain of the CRX1 and CRX2 channels independently. This is helpful if your CRX1 channel and CRX2 channel have different loss that need to be compensated for. If both CRX1 and CRX2 have similar loss, I recommend keeping EQCFG at "0/F" and using table 6-2 for the CRX EQ gain.

Let me know if you have any questions.

Best,

Shane