DS125DF1610 Datasheet, PDF (19/81 Pages) Texas Instruments – 9.8 to 12.5 Gbps 16-Channel Retimer

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DS125DF1610
SNLS482A – APRIL 2014 – REVISED DECEMBER 2015
7.3.8 Differential Driver with FIR Filter
The DS125DF1610 uses a 3-tap FIR filter to assist with transmit equalization. The FIR filter consists of a pre
cursor tap, a main cursor tap and a post cursor tap. Each tap has a polarity bit and 64 available levels. By
default, the main cursor tap is set to a positive polarity, while the pre cursor and post cursor taps are set to a
negative polarity. Users can invert the polarity of all 3 FIR taps to invert the polarity of the output data.
The DS125DF1610 output driver can be manually powered off through SMBus register control.
7.3.9 Setting the Output V_OD
The output differential voltage (V_OD) of the driver is controlled by manipulating the drv_sel_vod bits, DEM bits,
and FIR main cursor tap. The Table 6 below shows various settings for V_OD settings ranging from 150mV_PP to
1200 mV_PP. Using the FIR, DEM and drv_sel_vod bits is the recommended method for configuring the output
V_OD for the best signal integrity.
V_OD (mV_PP)
1200
1150
1100
1050
1000
950
900
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
DEM SETTING
0
0
0
0
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
Table 6. Typical V_OD Settings
drv_sel_vod
SETTING
PRE
31
0
31
0
31
0
31
0
31
0
31
0
31
0
31
0
31
0
25
0
25
0
25
0
21
0
19
0
17
0
15
0
13
0
12
0
10
0
8
0
6
0
4
0
FIR
MAIN
56
52
49
45
54
56
52
46
42
56
46
40
50
50
52
50
52
51
51
55
56
57
POST
-4
-4
-4
-4
-3
-2
-2
-1
-1
-3
-2
-1
-2
-3
-3
-3
-3
-3
-3
-3
-3
-3
7.3.10 Output Driver Polarity Inversion
In some applications it may be necessary to invert the polarity of the data transmitted from the retimer. To invert
the polarity of the data read back the FIR polarity settings for the pre, main and post cursor taps and then invert
these bits.
7.3.11 Driver Output Rise/Fall Time
In some applications, a longer rise/fall time for the output signal is desired. This can reduce electromagnetic
interference (EMI) generated by fast switching waveforms. This is necessary in some applications for regulatory
compliance. In others, it can reduce the crosstalk in the system.
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