DS125BR800A Datasheet, PDF (36/53 Pages) Texas Instruments – Low-Power 12.5-Gbps 8-Channel (Unidirectional) Repeater With Input Equalization

DS125BR800A
SNLS467 – NOVEMBER 2013
www.ti.com
Figure 7 depicts different transmission line topologies which can be used in various combinations to achieve the
optimal system performance. Impedance discontinuities at the differential via can be minimized or eliminated by
increasing the swell around each hole and providing for a low inductance return current path. When the via
structure is associated with thick backplane PCB, further optimization such as back drilling is often used to
reduce the detrimental high frequency effects of stubs on the signal path.
POWER SUPPLY BYPASSING
Two approaches are recommended to ensure that the DS125BR800A is provided with an adequate power
supply. First, the supply (VDD) and ground (GND) pins should be connected to power planes routed on adjacent
layers of the printed circuit board. The layer thickness of the dielectric should be minimized so that the V_DD and
GND planes create a low inductance supply with distributed capacitance. Second, careful attention to supply
bypassing through the proper use of bypass capacitors is required. A 0.1 μF bypass capacitor should be
connected to each V_DD pin such that the capacitor is placed as close as possible to the DS125BR800A. Smaller
body size capacitors can help facilitate proper component placement. Additionally, capacitor with capacitance in
the range of 1 μF to 10 μF should be incorporated in the power supply bypassing design as well. These
capacitors can be either tantalum or an ultra-low ESR ceramic.
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