ZHCSME1C August 2018 – June 2021 DS250DF230
PRODUCTION DATA
The output differential voltage (VOD), pre-cursor, and post-cursor equalization of the driver is controlled by manipulating the FIR tap settings. The main cursor tap is the primary knob for amplitude adjustment. The pre- and post-cursor FIR tap settings can then be adjusted to provide equalization. To maintain a constant peak-to-peak VOD, the user must adjust the main cursor tap value relative to the pre- and post-cursor tap changes so as to maintain a constant absolute sum of the FIR tap values. Table 8-2 shows various settings for VOD settings ranging from 350 mVpp to 1195 mVpp (typical). Note that the output peak-to-peak amplitude is a function of the sum of the absolute values of the taps, whereas the low-frequency amplitude is purely a function of the main-cursor value.
FIR SETTINGS | Peak-to Peak VOD(V) | RPRE(dB) | RPST(dB) | ||
---|---|---|---|---|---|
PRE-CURSOR: REG_0x3E[6:0] | MAIN-CURSOR: REG_0x3D[6:0] | POST-CURSOR: REG_0x3F[6:0] | |||
0 | +3 | 0 | 0.350 | NA | NA |
0 | +4 | 0 | 0.392 | NA | NA |
0 | +5 | 0 | 0.436 | NA | NA |
0 | +6 | 0 | 0.482 | NA | NA |
0 | +7 | 0 | 0.524 | NA | NA |
0 | +8 | 0 | 0.562 | NA | NA |
0 | +9 | 0 | 0.602 | NA | NA |
0 | +10 | 0 | 0.638 | NA | NA |
0 | +11 | 0 | 0.678 | NA | NA |
0 | +12 | 0 | 0.710 | NA | NA |
0 | +13 | 0 | 0.748 | NA | NA |
0 | +14 | 0 | 0.782 | NA | NA |
0 | +15 | 0 | 0.816 | NA | NA |
0 | +16 | 0 | 0.846 | NA | NA |
0 | +17 | 0 | 0.880 | NA | NA |
0 | +18 | 0 | 0.910 | NA | NA |
0 | +19 | 0 | 0.944 | NA | NA |
0 | +20 | 0 | 0.968 | NA | NA |
0 | +21 | 0 | 0.998 | NA | NA |
0 | +22 | 0 | 1.028 | NA | NA |
0 | +23 | 0 | 1.056 | NA | NA |
0 | +24 | 0 | 1.076 | NA | NA |
0 | +25 | 0 | 1.096 | NA | NA |
0 | +26 | 0 | 1.120 | NA | NA |
0 | +27 | 0 | 1.140 | NA | NA |
0 | +28 | 0 | 1.155 | NA | NA |
0 | +29 | 0 | 1.175 | NA | NA |
0 | +30 | 0 | 1.185 | NA | NA |
0 | +31 | 0 | 1.195 | NA | NA |
0 | +16 | –1 | 0.880 | NA | 2.0 |
0 | +15 | –2 | 0.880 | NA | 2.7 |
0 | +14 | –3 | 0.880 | NA | 3.4 |
0 | +13 | –4 | 0.880 | NA | 4.3 |
0 | +12 | –5 | 0.880 | NA | 5.4 |
0 | +11 | –6 | 0.880 | NA | 6.7 |
0 | +10 | –7 | 0.880 | NA | 8.4 |
0 | +9 | –8 | 0.880 | NA | 11 |
-1 | +16 | 0 | 0.880 | 0.7 | NA |
-2 | +15 | 0 | 0.880 | 1.5 | NA |
-3 | +14 | 0 | 0.880 | 2.5 | NA |
-4 | +13 | 0 | 0.880 | 3.5 | NA |
0 | +30 | –1 | 1.195 | NA | 0.6 |
0 | +29 | –2 | 1.195 | NA | 0.8 |
0 | +28 | –3 | 1.195 | NA | 1.1 |
0 | +27 | –4 | 1.195 | NA | 1.4 |
0 | +26 | –5 | 1.195 | NA | 1.8 |
0 | +25 | –6 | 1.195 | NA | 2.3 |
0 | +24 | –7 | 1.195 | NA | 2.8 |
0 | +23 | –8 | 1.195 | NA | 3.4 |
0 | +22 | –9 | 1.195 | NA | 4.1 |
0 | +21 | –10 | 1.195 | NA | 4.9 |
0 | +20 | –11 | 1.195 | NA | 5.9 |
0 | +19 | –12 | 1.195 | NA | 6.9 |
-1 | +30 | 0 | 1.195 | 0.4 | NA |
-2 | +29 | 0 | 1.195 | 0.6 | NA |
-3 | +28 | 0 | 1.195 | 0.9 | NA |
-4 | +27 | 0 | 1.195 | 1.3 | NA |
-5 | +26 | 0 | 1.195 | 1.7 | NA |
-6 | +25 | 0 | 1.195 | 2.1 | NA |
-7 | +24 | 0 | 1.195 | 2.7 | NA |
The recommended pre-cursor and post-cursor settings for a given channel will depend on the channel characteristics (mainly insertion loss) as well as the equalization capabilities of the downstream receiver. The DS250DF230 receiver, with its highly-capable CTLE and DFE, does not require a significant amount of pre- or post-cursor. The guidelines in Figure 8-5 through Figure 8-7 give general recommendations for pre- and post-cursor for different channel loss conditions. The insertion loss (IL) in these plots refers to the total loss between the link partner transmitter and the DS250DF230 receiver.