SLASEW5 December 2020 TMUXHS4412
The TMUXHS4412 has a weak pull-down of 1MΩ from D[0/1/2/3][P/N] pins to GND. While these resistors biases the device data channels to common mode voltage (CMV) of 0 V with very weak strength, it is recommended that the device is biased by a stronger impedance from either side of the device to a valid value. To avoid double biasing appropriate AC coupling capacitors should be ensured on either side of the device.
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 CMV range for each D[0/1/2/3][P/N] pin will suffice for most use cases.
The high-speed data ports incorporate 20 kΩ pull-down resistors that are switched in when a port is not selected and switched out when the port is selected. For example when SEL = L, the DB[0/1/2/3][P/N] pins have 20 kΩ resistors to GND. The feature ensures that unselected port is always biased to a known voltage for long term reliability of the device and the electrical channel.
The positive and negative terminals of data pins D[0/1/2/3] have a weak (20 kΩ) differential resistor in between them for device switch regulation operation. This does not impact signal integrity or functionality of high speed differential signaling that typically has much stronger differential impedance (such as 100 Ω).