Применения > > Universal Serial Bus (USB) Peripheral Isolator Circuit

Universal Serial Bus (USB) Peripheral Isolator Circuit (cn0160)

The universal serial bus (USB) is rapidly becoming the standard interface for most PC peripherals. It is displacing RS-232 and the parallel printer port because of superior speed, flexibility, and support of device hot swap. There has been a strong desire on the part of industrial and medical equipment manufacturers to use this bus as well, but adoption has been slow because there has not been a good way to provide the isolation required for connections to machines that control dangerous voltages or low leakage defibrillation proof connections in medical applications.

The ADuM4160 provides an inexpensive and easy to implement isolation buffer for medical and industrial peripherals. The challenges that need to be met are:

  1. Isolate directly in the USB D+ and D− lines allowing the use of existing USB infrastructure in microprocessors.
  2. Implement an automatic scheme for data flow of control that does not require external control lines.
  3. Provide medical grade isolation.
  4. Allow a complete peripheral to meet the USB-IF certifi-cation standards.
  5. Support full speed (12 Mbps) and low speed (1.5 Mbps) signaling rates.
  6. Support flexible power configurations.

The circuit shown in Figure 1 isolates a peripheral device that already supports a USB interface. Because the peripheral is not explicitly defined in this circuit, power to run the secondary side of the isolator has been provided as part of the solution. If the circuit is built onto the PCB of a peripheral design, power could be sourced from the peripheral’s off line supply, a battery, or the USB cable bus power, depending on the needs of the application.

The application circuit shown is typical of many medical and industrial applications.

Figure 1. USB Peripheral Isolator Circuit


  • Isolation from USB peripheral device
  • Standard USB interface


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