Abstract:
This invention describes a means by which a communication data bus can be electrically isolated from noise generating electrical devices such as electromagnetic actuators, which are controlled by data from the bus, using a single integrated circuit package. Specifically, an all silicon optically isolated interface within the package is used to galvanic insulate the circuitry associated with the data bus interface from the circuitry operating or receiving data from devices such as motors, sensors, etc. that are connected to a noisy environment.

Description:
RELATED APPLICATION  
       [0001]     This Application claims the benefit of Provisional Application Ser. No. 60/673,579, filed on Apr. 22, 2005. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable  
       REFERENCE TO A MICROFICHE APPENDIX  
       [0003]     Not Applicable  
       FIELD OF THE INVENTION  
       [0004]     This invention relates to computer communication bus interface applications using optically coupled electronic integrated circuits, and more particularly to applications in which data from a computer communication bus is electrically isolated from devices that are being controlled by the computer.  
       BACKGROUND  
       [0005]     Controller or communication buses are used to send and receive data from devices to a controlling computer. The devices can include actuators such as electric motors, relays, and solenoids, display devices, light sources, heat sources, and sensors such as, but not limited to, pressure sensors, temperature sensors, electrical current sensors, voltage sensors, and position sensors. Thus, a controlling computer can send data down the bus to, say, turn on an electric motor, or turn off a light, or to sound a buzzer, or to up date display information. Also, a controlling computer can receive data form the bus that comes from sensors. Furthermore, the controlling computer can send and receive data from a secondary computer. Communication bus standards include CAN, SAFEbus (avionics bus for aircraft), MicroLAN, I 2 C-bus, PROFIBUS, RS232, and RS485. For automotive applications there is FlexRay and Time-Triggered Architecture (TTA).  
         [0006]     There can be devices that are controlled by a communication bus that generate electrical noise and electrical transient spikes such as electric motors and solenoids. For these cases an opto-coupler can be used to electrically isolate the communication bus from the noise generating device being controlled by the bus. Thus, the opto-coupler prevents noise from the noise generating device from corrupting communication bus data.  
         [0007]     In the simplest opto-couplers there are two devices, a Light Emitting Diode (LED) and a light detector. The LED is usually made of doped GaAsP material. The LED and the light detector are separated by a transparent, insulating layer thereby allowing light to pass through but not electrical current. The detector is typically a single device such as a diode, a bipolar transistor, an SCR, or a Triac. Detector chips may also include circuits such as amplifiers and various types of output buffer/drivers. Moreover, an additional silicon chip can be added as a input buffer/driver for the LED. The input signal may be, for example, a TTL type, which can not directly drive the LED. Since the LED diver chip must be isolated from the detector chip, three separate chips are thus required in this case: the silicon LED driver chip, the GaAs based LED, and the detector chip.  
         [0008]     Using available parts, to interface a noisy device to a communication bus typically requires several integrated circuits or chips as shown in  FIG. 1 . Two optically isolated data paths are shown, one in which data from the communication bus  101  is transmitted to Device  109  which can be, for example, a motor to be controlled, a solenoid, etc, and a second data path in which the communication bus  101  receives data from Device  2   110  which can be, for example, a temperature sensor, pressure transducer, etc.  
         [0009]     For the first data path data is received from the communication bus  101 . This is accomplished by the address of the Data Bus Receiver  103  first being transmitted on  101 . The transmission of the Data Bus Receiver&#39;s  103  address on bus  101  tells the Data Bus Receiver  103  that data intended for it will transmitted next. The data is then fed to an LED Driver  104 , which in turn controls the light output of an LED in the optocoupler  105 . In the diagram of  FIG. 1 a  simple optocoupler is shown with an LED made of GaAsP and a bipolar photo transistor that is used as a light detector. It is noted that the optocoupler  105  is for illustration purposes and that a more complex optocoupler could have also been used. The output of the optocoupler  105  is then fed to an optocoupler receiver  106 . The receiver  106  can be anything from a load resistor for the photo transistor to an amplifier. The output of the Opto Coupler Receiver  106  is then fed to a Device 1  Driver  107 , which in turn drives Device 1   109 . Device Driver 1   107  could, for example, be a power switch MOSFET used to turn an electric motor, solenoid, etc. “on” and “off”.  
         [0010]     In the reverse direction, data is generated from Device 2   110 . This data could include temperature data, pressure data, position data, etc. The data is then received by Device 2  Receiver  111 . The Device 2  Receiver  111  can be an amplifier followed by an Analog to Digital (A to D) converter, for example. The Device 2  Receiver  111  then sends signals to the LED Driver  112 , which in turn controls the light output of the LED of the optocoupler  113 , which, again by way of illustration, is a simple LED-Photo transistor type. The output of the optocoupler  113  is fed to the Opto Coupler Receiver  114  that interfaces with photo transistor&#39;s output to the Data Bus Transmitter  115 . Finally, the data from Device 2   110  is transmitted to the controller data bus by the Data Bus Transmitter  115 . In general the Data Bus Receiver  103  and the Data Bus Transmitter  115  are on one chip. An example of a data bus transceiver that communicates with an I 2 C bus to provide an 8 bit I/O is the Phillips PCF8574 chip.  
         [0011]     Sophisticated optocouplers can be realized using silicon LEDs. Silicon LEDs can be made using a PN junction in the avalanche mode (U.S. Pat. No. 6,365,951) or PN junctions in the forward mode (U.S. Pat. No. 6,710,376), especially if the junction area has damage to enhance light emission. In the avalanche mode the light emission is in the visible spectrum centered in the yellow region while in the forward biased mode it is in the infrared region.  
         [0012]      FIG. 2  shows an example of the package construction of an all silicon opto-coupler (U.S. Pat. No. 6,393,183).  FIG. 2A  is the top view of the package and  FIG. 2B  is a cross section. The package  200  shown is a flat pack with two rows of leads, a left side  211  and a right side  212 . The row of leads on the left side  211  is electrically isolated from the row of leads on the right side  212 .  
         [0013]     The cross section shows two silicon die,  205  and  206 , facing each other and separated by a transparent insulator  207 . Bond wire  208  goes from a package lead  202  associated with the 211 row of leads to a bond pad of die  205  and bond wire  204  goes from package lead  203  to a bond pad of die  206 . The die  205  is attached to the upper lead frame base plate  210  and die  206  is attached to the lower lead frame base plate  209 . The entire structure is surrounded by a plastic encapsulent  201 . Light  213  is shown being transmitted from an silicon based LED  214  on die  206  to a light detector  215  on die  205 . Thus, in this example, light is transmitted from one die  206  to a second die  205  that is electrically isolated from the first die  206 . Signal communication is therefore made between die  205  and  206  without any electrical connection.  
       SUMMARY  
       [0014]     It is the objective of this invention to show how low efficiency, on chip silicon LEDs can be used to realize integrated circuits than can receive and transmit signals form a controller or communication bus and deliver or receive signals from a device to be controlled without any electrical connection between the bus and the device. Specifically, these integrated circuits include at least a bus interface circuit for transmitting and receiving bus data, one or more silicon LEDs, one or more silicon light detectors, one or more amplifiers for the light detector signal, one or more drivers for the LED, and device drivers and/or receivers. Depending on the application, data formatting may be required and A to D and D to A converters may also be required. Data formatting involves taking data from a device or plurality of devices and streaming the data through the optocoupler or, conversely, receiving data streams from the optocoupler and reformatting it for a device or a plurality of devices. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1 . shows a block diagram of a optically isolated communication bus to device circuit that can transmit and receive signals from devices and is made up of several discrete, off the shelf integrated circuits.  
         [0016]      FIG. 2  shows a prior art to view and cross section of an all silicon opto-coupler package with a silicon LED  
         [0017]      FIG. 3  shows a single package, optically isolated, communications bus to device integrated circuit comprised of two integrated circuits with integrated silicon LEDs.  
         [0018]      FIG. 4  shows a device side integrated circuits than can control a plurality of devices and can receive data from a plurality of devices. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]      FIG. 3  shows an example of an optically isolated bus interface circuit, which is able to transmit and receive data from a communication bus  101  and send the control information inherent in the bus data to a device  309  or send information from a device  310  to the bus  101 . Two integrated circuits or chips,  320  and  321 , which are placed in a single package  323  as depicted in  FIG. 2 , are required to perform the aforementioned functions. Chip  320  is associated with electrical circuit side that deals with direct bus communications while chip  321  is associated with the electrical circuit side that deals with the device to be controlled. Thus, chip  320  will be referred to as the bus communication side chip and chip  321  as the device side chip. Data transfer between the two isolated electrical circuit sides is accomplished with pairs of integrated silicon LEDs and light detectors. The silicon LEDs are integrated onto the silicon substrate and may be fabricated by any number of means such as porous silicon, avalanching silicon PN junction, or forward biased silicon PN junction. Furthermore, these applications can be realized using low efficiency, silicon based LEDs. Chip  320  can correspond to either chip  205  or  206  of  FIG. 2  while chip  321  corresponds to the opposite chip. Note that light can be both transmitted and received by the same chip by simply locating the LED and light detector well away from each other so that there is no interaction.  
         [0020]     For the receive path from the communication bus  101  to Device 1   309  there is the Data Bus Receiver  303  which extracts input data from the bus  101 . To identify data that is to be transmitted to the Data Bus Receiver  303  address information is first transmitted on the bus  101 . When there is a match between the address transmitted on the bus  101  and the address  322  input to the Data Bus Receiver  303  the Data Bus Receiver  303  is then put into the receive mode and begins to receive subsequent data from bus  101 . The bus address  322  can come from an external source as shown in  FIG. 3  which can include hard wired address pins, or from a hard wire connection internal to the chip with no address pin leads passing outside the chip. Other possible address sources include poly silicon fuses internal to chip  320  that are blown according to a desired bus address or an EPROM internal to chip  320  that can be reprogrammed from the data bus input pins.  
         [0021]     Data from the data bus  101  targeted for part  323  is collected by the Data Bus Receiver  303  and then formatted for transmission serially to the device chip  321 . Thus, the Data Bus Receiver  303  can buffer data that comes from the bus  101  at a rate faster than can be transmitted via the optical data link comprising LED  305  and photo detector  319 . Therefore, the data is converted by LED  305  into light  324  pulses that are received by photo detector  319 , which, in turn, converts the light  324  pulses back into electrical pulses. The electrical pulses produced by the photo detector  319  mirror the serial data stream input to the LED  305 . The Opto Coupler Receiver  306  amplifies the photo detector signal and generates logic level signals. The Device 1  Driver  307  accepts the data from the Opto Coupler Receiver  306  and uses it to control Device 1   309 .  
         [0022]     In the reverse direction data from Device 2   310  can be sent to the Communications Bus  101 . The reverse direction data transfer begins by electrical data from Device 2   310  being sent to the Device 2  Receiver  311  of chip  321 . The data can be buffered, as an option, by the Device 2  Receiver  311  if the optical transmission rate is lower than the data generation rate. The data from the Device 2  Receiver  311  then drives the LED  314  with electrical pulses corresponding to the data originally input from Device 2   310 . Light  325  pulses from LED  314  is then received by photo detector  318  and converted back into electrical pulses. The electrical pulses from photo detector  318  are amplified by the Opto Coupler Receiver  315  and sent as logical data pulses to the Data Bus Transmitter  316 . The Data Bus Transmitter  316  can, as an option, buffer the data such that data can be collected over time from the optical link comprising LED  314  and photo detector  318  and then transmitted in a burst mode out onto the Communications Bus  101  via the Data Bus Transmitter  316 .  
         [0023]     Power for the chip  320  associated with the data bus side is supplied by Vdd 1   302  and Vss 1   317  and power for the chip  321  associated with the device side is supplied by Vdd 2   308  and Vss 2   312 .  
         [0024]      FIG. 4  shows how the device side chip that can be architected to control and receive data from many different devices. The device side chip  421  corresponds to the device side chip  321  of  FIG. 3  but includes a plurality of device ports for controlling a plurality of devices and receiving data from a plurality of sensors. As in  FIG. 3 , a photo detector  404  receives light  405  from an LED located on the data bus chip side such as integrated circuit  320  of  FIG. 3 . The data stream is received by the Opto Coupler Receiver  406  where the photo detector signal is amplified and converted into a digital data signal. This data signal is then sent to the Receive Data Formatter/Multiplexer  407  where the data formatted for a plurality of output devices. The Receive Data Formatter/Multiplexer  407  then outputs the data to the appropriate devices. As examples, but not limited to, are a D to A converter  409  which can output a voltage or current in response to digital data, an NFET power switch  411  to ground or Vss 2 , a PFET power switch  410  to Vdd 2 , and an inverter  412  that can output a digital signal.  
         [0025]     A plurality of devices can also input data to integrated circuit  421 . As an example, but not limited to, are an inverter  413  than can receive a digital signal, and an A to D converter  415  which is shown with multiplexed analog inputs. The input multiplexer  414  is used to sample analog signals from a plurality of sources. Alternatively, if only one analog signal is to be received or it is required that the analog signal be sampled frequently then package pin input can be directly connected to the input  419  of the A to D converter  415 , or for a plurality of inputs requiring frequent sampling, a plurality of A to D converters. Control of the analog multiplexer  414  comes from digital signals output from the Receive Data Formatter/Multiplexer  407 .  
         [0026]     Data from a plurality of devices such as, but not limited to, inverter  413  and A to D converter  415 , are received by the Transmit Data Formatter/Demultiplexer  416 . The Transmit Data Formatter/Demultiplexer  416  takes the data from a plurality of devices and formats the data for serial transmission through the optical link comprising LED  402  and a photo detector not shown but similar to  318  of  FIG. 3 . LED Driver  418  takes the digital data stream and uses it to pulse the LED  402  according the digital data stream. Light  403  is then emitted from LED  402  for reception by the photo detector on the communication bus side integrated circuit such as  320  of  FIG. 3 .  
         [0027]     While the invention is susceptible to various modifications, and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but to the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the appended claims.