8 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification, and TI

does not warrant its accuracy or completeness. TI’s customers are responsible for determining

suitability of components for their purposes. Customers should validate and test their design

implementation to confirm system functionality.

8.1 Application Information

The TMUXHS4412 is an analog 4-channel high-speed mux/demux type of switch that can be used for routing

high-speed signals between two different locations on a circuit board. The TMUXHS4412 can be used for many

high speed interfaces including:

• Peripheral Component Interconnect Express (PCIe) Gen 1.0, 2.0, 3.0, 4.0

• USB 4.0

• Universal Serial Bus (USB) 3.2 Gen 1.0, 2.0

• Serial ATA (SATA/eSATA)

• Serial Attached SCSI (SAS)

• Display Port (DP) 1.4, 2.0

• Thunderbolt (TBT) 3.0

• Mipi Camera Serial Interface (CSI-2), Display Serial Interface (DSI)

• Low Voltage Differential Signalling (LVDS)

• Serdes Framer Interface (SFI)

• Ethenet Interfaces

The device’s mux/demux selection pin SEL can easily be controlled by an available GPIO pin of a controller or

hard tie to voltage level H or L as an application requires.

The TMUXHS4412 with adaptive voltage tracking technology can support applications where the common mode

is different between the RX and TX pair. The switch paths of the TMUXHS4412 have internal weak pull-down

resistors of 1 MΩ on the common port pins. While these resistors biases the device data channels to common

mode voltage (CMV) of 0 V with a weak strength, it is recommended that the device is biased from either side of

the device to a valid value (in the range of 0 - 1.8 V in 3.3 V supply voltage mode). It is expected that the system/

host controller and Device/End point common mode bias impedances are much stronger (smaller) than the

TMUXHS4412 internal pull-down resistors; therefore, they are not impacted.

Many interfaces require AC coupling between the transmitter and receiver. The 0201 or 0402 capacitors are the

preferred option to provide AC coupling. Avoid the 0603, 0805 size capacitors and C-packs. When placing AC

coupling capacitors, symmetric placement is best. The capacitor value must be chosen according to the specific

interface the device is being used. The value of the capacitor should match for the positive and negative signal

pair. For many interfaces such as USB 3.2 and PCIe, the designer should place them along the TX pairs on the

system board, which are usually routed on the top layer of the board. Depending upon the application and

interface specifications, use the appropriate value for AC coupling capacitors.

The AC coupling capacitors have several placement options. Typical use cases warrant that the capacitors are

placed on one side of the TMUXHS4412. In certain use cases, if both side of the TMUXHS4412 is ac coupled, it

is recommended that appropriate CMV biasing is used for the device. 10 kΩ to GND or any other bias voltage in

the valid CMV range for each D[0/1/2/3][P/N] pin of the common port suffice for most use cases. Figure 8-1

shows a few placement options. Note for brevity not all channels are illustrated in the block diagrams. Some

interfaces such as USB SS and PCIe recommends AC coupling capacitors on the TX signals before it goes to a

connector. Option (a) features TX AC coupling capacitors on the connector side of the TMUXHS4412. Option (b)

illustrates the capacitors on the host of the TMUXHS4412. Option (c) showcases where the TMUXHS4412 is ac

coupled on both sides. VBIAS must be within the valid CMV of the device.

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TMUXHS4412

SLASEW5 – DECEMBER 2020

Copyright © 2020 Texas Instruments Incorporated

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