LMH0340SQE Datasheet, PDF (11/30 Pages) Texas Instruments – 3 Gbps, HD, SD, DVB-ASI SDI Serializer and Cable Driver With LVDS Interface

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LMH0040, LMH0050
LMH0070, LMH0340
SNLS271I – APRIL 2007 – REVISED APRIL 2013
2.5V
TXOUT+
TXOUT-
2.5V
24 mA
Figure 6. Simplified SDI Output Circuit
Care must be taken in the layout of the output circuitry to meet SMPTE return loss specifications as any parasitic
impedances or transmission line discontinuities will result in reflections which will adversely affect the output
return loss. For more details on how to get good output return loss, please refer to the application note
“Successful design with the FPGA-Attach SER/DES”.
0
-10
SMPTE424 Limit
-20
-30
Measured EVK
Return Loss
-40
-50
-60
1.00E+07
1.00E+08 1.00E+09
FREQUENCY
1.00E+10
Figure 7. SDI Output Return Loss (EVK Example)
The amplitude of the output is ensured to be compliant with SMPTE specifications if the specified value of R_SET
resistor is used, however if the designer wishes to change the output amplitude, there are two methods by which
this can be done. By changing the value of resistor connected to the R_SET pin, the output amplitude will be
adjusted.
1000
950
900
850
800
750
700
650
600
6
7
8
9
10
11
RSET (k:)
Figure 8. Output Voltage vs. R_SET
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