SLAU823 October   2019 TMUXHS4212

 

  1.   TMUXHS4212 Evaluation Module User's Guide
    1.     Trademarks
    2. 1 Introduction
    3. 2 Setup and Configuration
      1. 2.1 Signal Connection
      2. 2.2 AC Coupling Capacitors
      3. 2.3 Jumper Configuration
      4. 2.4 Power
      5. 2.5 Calibration
      6. 2.6 REACH Compliance
    4. 3 Schematics
    5. 4 Bill of Materials
      1. 4.1 TMUXHS4212EVM BOM

2.2 AC Coupling Capacitors

Most interfaces require AC coupling between the transmitter and receiver. The USB 3.1 specification requires AC coupling capacitors in the range of 75 - 265 nF for Gen 1 and Gen 2 speeds. By default, the EVM is populated with 220 nF AC coupling capacitors on Ports B and C. The 220 nF value was chosen over the more typical 100 nF value to maintain spec compliance when the host or device attached to the EVM also has a capacitor in series. Port A is populated with 0 Ω resistors which can be replaced with capacitors if needed. However, the TMUXHS4212 switch requires a bias voltage so capacitors cannot be placed on both sides of the switch unless an external bias voltage of < 2 V is provided. The TMUXHS4212 Two-Channel Differential 2:1/1:2 USB3.1 Mux/Demux datasheet has additional information about implementing coupling capacitors and bias voltage for various applications.