Device/

EndPoint

Device/

EndPoint

Host

Device/EndPoint Board

Device/EndPoint Board

TX

RX

TX

RX

TX

RX

Host Board

Device/

EndPoint

Device/

EndPoint

Host

Device/EndPoint Board

Device/EndPoint Board

TX

RX

TX

RX

TX

RX

Host Board

TX

RX

TX

RX

RX

RX

TX

TX

TX

TX

RX

RX

Device/

EndPoint

Device/

EndPoint

Device/EndPoint Board

Host Board

Device/EndPoint Board

TX

RX

TX

RX

Host

TX

RX

VBIAS

VBIAS

(b)

(c)

(a)

Figure 8-1. AC Coupling Capacitors Placement Options between Host and Device / Endpoint

8.2 Typical Applications

8.2.1 PCIe Lane Muxing

The TMUXHS4412 can be used to switch PCIe lanes between two slots. In many PC and server motherboards,

the CPU does not have enough PCIe lanes to provide desired system flexibility for end customers. In such

applications, the TMUXHS4412 can be used to switch PCIe TX and RX lanes between two slots. Figure 8-2

provides a schematic where four TMUXHS4412 are used to switch eight PCIe lanes (8-TX and 8-RX channels).

Note the common mode voltage (CMV) bias for the TMUXHS4412 must be within the valid range. In

implementations where receiver CMV bias of a PCIe root complex or an end point can not be ensured within the

CMV range, additional DC blocking capacitors and appropriate CMV biasing must be implemented. One side of

the device has AC coupling capacitors. Additionally the PD pin must be low for device to work. This pin can be

driven by a processor.

TMUXHS4412

SLASEW5 – DECEMBER 2020

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