Hello,
i use two DS125BR401 PCIe redrivers on a express carrier card. During the development of this carrier card, specially the configuration of the equalizer and deemphasis settings,
i have problems with different pcie addon cards to get a stable Gen3 link or good Gen3 speed. Some cards work fine but a few have problems.
I tried different strappings for the equzalizer and deemphasis settings. The best results i have made with the following setting:
Upstream side: EQ -> Level 2 (5-10 inch trace)
DE -> Level 3 (10 inch trace)
Downstream side: EQ -> Level 2 (5-10 inch trace)
DE -> Level 3 (10 inch trace)
The complete routing of the upstream side is round about 150mm and of the downstream side round about 250mm.
I use the Webench Design Tool for the redriver to optimize the strappings. A good result is simulated for the EQ on the up- and downstream side with Level 1 (Level 2 in databook) and
for the deemphasis with VOD 0.9V and DEM in db with -3,5dB (it correspndends with Level 3 in the databook).
The first question i have, if i understand right the strappings for the EQ and deemphasis. The length for the TX path (redriver output to the RX root complex) corresondends with the deemphasis setting and the the RX path (redriver input to TX of the root complex) to the equalizer setting?
There is also a mode operation with Pin control (databook page 14). I set the mode to Float (default -> automatic). I think this is right for PCIe?
Unfortunately i can not measure an eye diagram at the hardware. I hope someone have a hint or tip for a configuration.
Thank you,
Marcel
