SLYT834 March   2023 ISOUSB211

 

  1. 1 Introduction
  2. 2 Existing implementation of OTG USB applications
  3. 3  On-the-go operation
  4. 4 Implementation of isolated OTG
  5. 5 Demonstration of OTG with ISOUSB211 EVM
  6. 6 Scenario A: Isolated OTG module connected to a USB-drive (bus-powered)
  7. 7  Scenario B: Isolated OTG module connected to a laptop (host)
  8. 8 Demonstration
  9. 9 Connect phone to laptop
  10. 10Connect phone to USB-drive
  11. 11Summary

2 Existing implementation of OTG USB applications

Existing approach for implementing isolated USB platforms have been with recommendations around providing dedicated host and peripheral ports for establishing the datalink as shown in #FIG_R45_JK1_MVB. The upstream-facing (peripheral) port has the D+ pulled up (indicating a full or high-speed peripheral) or D- pulled up (indicating a low-speed peripheral) through a 1.5-kΩ resistor. The downstream facing (host) device has the 15-kΩ pull-down resistors as per USB2.0 standard. Downstream-facing port powers the 5-V VBUS rail and does not draw power from the upstream facing port. Once the connect is established, the presence of VBUS is detected after which pullup identification and packet transactions occur. Therefore, for an isolated OTG implementation in which the port must assume either a host or a peripheral role, the isolator must be transparent to the connection.

Figure 2-1 Separate host and peripheral implementation.