USB isolator with advanced control features

Abstract

A USB-based isolator system conveys USB signals between a pair of galvanically isolated circuit systems and supports controlled enumeration by a downstream device on upstream USB signal lines. The isolator system provides a multi-mode voltage regulator to support multiple voltage supply configurations. The isolator system further provides control systems for each of the isolated circuit systems and provides robust control in a variety of start up conditions. Additionally, the isolator system includes refresh timers and watchdog mechanisms to support persistent operation but manage possible communication errors that can arise between the isolated circuit systems.

We claim: 
     
       1. An isolation system, comprising:
 a plurality of isolation devices bridging an isolation barrier between an upstream side and a downstream side of the isolation barrier,   a USB interface provided on an upstream side of the isolation barrier, including a termination circuit having a pull up resistor,   an isolator transceiver coupling the USB interface to the isolation devices, and   an isolator transmitter provided on a downstream side of the isolation barrier to receive an enumeration control signal, wherein the enumeration control signal propagates through at least one of the isolation devices to the upstream side and controls switching of the pull up resistor in the termination circuit.   
     
     
       2. The isolation system of  claim 1 , wherein isolation devices are provided for each of a D+ and D− data signal of a USB protocol and a separate isolation device is provided for the enumeration control signal. 
     
     
       3. The isolation system of  claim 1 , wherein isolation devices are provided for each of a D+ and D− data signal of a USB protocol, and signals are encoded so the enumeration control signal can propagate through said isolation devices along with the D+ and D− data. 
     
     
       4. The isolation system of  claim 1 , wherein isolation devices are provided for each of a D+ and D− data signal of a USB protocol and are shared with the enumeration control signal. 
     
     
       5. The isolation system of  claim 1 , wherein the isolation devices are unidirectional isolation devices. 
     
     
       6. The isolation system of  claim 1 , wherein the isolation devices are bidirectional isolation devices. 
     
     
       7. The isolation system of  claim 1 , further comprising an input for a selection signal that identifies which one of the D+ and D− data lines is to be connected to the pull up resistor. 
     
     
       8. The isolation system of  claim 7 , wherein the input is provided on the upstream side of the isolation barrier. 
     
     
       9. The isolation system of  claim 7 , wherein the input is provided on the downstream side of the isolation barrier. 
     
     
       10. An isolation system, comprising:
 an isolation device bridging an isolation barrier between an upstream side and a downstream side;   the downstream side including:
 a downstream USB interface to determine an operating speed of a peripheral device, and 
 an isolator transmitter to transmit a control signal conveying the operating speed across the isolation barrier through the isolation device; and 
   the upstream side including:
 an upstream USB interface with a termination circuit including a pull up resistor, 
 an isolator receiver to receive the control signal from the downstream side and provide the received control signal to a controller, and 
 the controller to control switching of the pull up resistor based on the control signal received by the isolator receiver.  
   
     
     
       11. The isolation system of claim 10, wherein the isolation device is a first isolation device, and wherein the isolation system further comprises a second isolation device bridging the isolation barrier between the upstream side and the downstream side, wherein the second isolation device is provided for transmitting USB data signals.  
     
     
       12. The isolation system of claim 10, wherein the isolation device is shared for transmission of the control signal and USB data signals.  
     
     
       13. The isolation system of claim 10, further comprising an encoder provided at the downstream side to encode the control signal with USB data signals, wherein the encoded signal is to be transmitted through the isolation device.  
     
     
       14. The isolation system of claim 10, wherein the isolation device is unidirectional.  
     
     
       15. The isolation system of claim 10, wherein the isolation device is bidirectional.  
     
     
       16. The isolation system of claim 10, further comprising a pulse generator to generate the control signal, wherein the control signal is a pulse signal.  
     
     
       17. The isolation system of claim 10, further comprising a refresh timer to maintain one side of the isolation system in a reception state for communication across the isolation barrier during a watchdog interval.  
     
     
       18. A method, comprising:
 determining, at a first side of a galvanically isolated circuit system, an operating speed of a peripheral device connected by a first USB connection to the circuit system,   transmitting, from the first side of the circuit system to a second side of the circuit system and across an isolation barrier of the circuit system, a control signal identifying the operating speed of the first USB connection, and   receiving the control signal at the second side of the circuit system using an isolator receiver and providing the received control signal to a controller on the second side of the circuit system;   controlling, using the controller at the second side of the circuit system, one or more pull up resistors of a second USB interface at the second side according to the control signal received by the isolator receiver.    
     
     
       19. The method of claim 18, further comprising:
 transmitting, from the first side to the second side of the circuit system, USB data signals.    
     
     
       20. The method of claim 19, wherein the USB data signals and the control signal are transmitted through separate isolation devices.  
     
     
       21. The method of claim 19, wherein the USB data signals and the control signal are transmitted through a common isolation device.  
     
     
       22. The method of claim 21, further comprising:
 encoding the control signal with the USB data signals.    
     
     
       23. The method of claim 18, wherein determining the operating speed of the peripheral device includes monitoring signals of the first USB connection.  
     
     
       24. The method of claim 18, wherein the control signal is a pulse signal.  
     
     
       25. The method of claim 18, further comprising:
 maintaining one side of the isolated circuit system in a reception state for communication across the isolation barrier during a watchdog interval.    
     
     
       26. An integrated circuit that is configured to determine an operating speed of an isolated USB, comprising:
 an isolation barrier separating a first side and a second side of the integrated circuit;   a USB interface to determine an operating speed of a peripheral device;   an isolator transmitter, on the first side, to transmit a control signal conveying the operating speed across the isolation barrier;   an isolator receiver, on the second side, to receive the control signal from the first side and provide the control signal to a controller, and   the controller to control switching a termination circuit based on the control signal received by the isolator receiver.    
     
     
       27. The integrated circuit of claim 26, further comprising an isolation device for transmitting the control signal that is separate from another isolation device for transmitting USB data signals.  
     
     
       28. The integrated circuit of claim 26, wherein an isolation device is shared for the transmission of the control signal and USB data signals.  
     
     
       29. The integrated circuit of claim 26, further comprising an encoder provided at the first side to encode the control signal with USB data signals, wherein the encoded signal is to be transmitted through an isolation device.  
     
     
       30. The integrated circuit of claim 26, further comprising a capacitive isolation device bridging the isolation barrier between the first and second sides.  
     
     
       31. The integrated circuit of claim 26, further comprising a pulse generator to generate the control signal, wherein the control signal is a pulse signal.  
     
     
       32. The integrated circuit of claim 26, further comprising a refresh timer to maintain one side of the integrated circuit in a reception state for communication across the isolation barrier during a watchdog interval.