8.3.3 Continuous Time Linear Equalizer (CTLE)

The CTLE in the DS250DF210 is a fully-adaptive equalizer. The CTLE adapts according to a Figure of Merit (FOM) calculation during the lock acquisition process. The FOM calculation is based upon the horizontal eye opening (HEO) and vertical eye opening (VEO). Once the CDR locks and the CTLE adapts, the CTLE boost level is frozen until a manual re-adapt command is issued or until the CDR re-enters the lock acquisition state. The CTLE can be re-adapted by resetting the CDR.

The CTLE consists of 4 stages, with each stage having 2-bit boost control. This allows for 256 different boost combinations. The CTLE adaption algorithm allows the CTLE to adapt through 16 of these boost combinations. These 16 boost combinations comprise the EQ Table in the channel registers. See channel registers 0x40 through 0x4F in Table 6. This EQ Table can be reprogrammed to support up to 16 of the 256 boost settings.

The boost levels can be set between 8 dB and 25 dB (at 12.89 GHz.)