Cmos Isolators For Home Appliance Motor Control

Transcript

CMOS Isolators for Home Appliance Motor Control Introduction The home appliance market uses three-phase, pulse-width-modulated (PWM) motors in a number of end applications including air conditioners, washers, dryers and garage door openers. Many of these applications require variable speed and/or torque, and the controllers that provide this capability must be low-cost, reliable and efficient. Such controllers frequently require isolation for several circuits, such as the gate drive, current measurement, and control feedback paths. While optocouplers have traditionally provided this isolation, most designers have begun moving to complementary metallic oxide semiconductor (CMOS) isolators, which offer substantial improvements over optocouplers in the areas of performance, power, size, reliability and costper-channel. Optocoupler Technology vs. CMOS Isolator Technology An optocoupler is a hybridized device containing a light-emitting diode (LED), optically transparent insulating film (dielectric) and an output die containing a photo detector and output stage. Optocoupler operation is simple: the output-side photodetector converts light to current, which drives the output stage in proportion to LED brightness. In spite of this simple operating principle, optocouplers are notorious for relatively poor performance and reliability due to their underlying process and packaging technologies. Light emissions from the Gallium Arsenidebased (GaAs) LED change with temperature and device age, complicating design and often forcing design compromises. LEDs also have an intrinsic wear-out mechanism (“LOP”) that permanently reduces LED emissions by 20% or more and is worsened by elevated temperature and LED current. This reduction in LED output further worsens optocoupler timing and output drive performance. The single-ended architecture of optocouplers (and high internal capacitive coupling) results in poor common-mode transient immunity (CMTI), which can increase optocoupler error rates in electrically noisy environments. These and other issues (e.g. high power consumption, external BOM and large footprint per channel) require added design efforts to compensate for the fundamental weaknesses of optocouplers. Silicon Labs CMOS isolators use conventional CMOS process technology and ON/OFF keying modulation to transmit digital data through the isolation barrier and offer superior performance and reliability compared to optocouplers. These key technology differences are: • The Use of Mainstream, Low-Power CMOS Process Technology Instead of GaAs CMOS is arguably the most robust, best performing and most widely sourced process technology in the world. CMOS offers very high device integration and speed, low-power operation and exceptionally high reliability. The combination of advanced circuit design techniques and CMOS processing enable Silicon Labs’ fast 150 Mbps data rate (tPD = 10 ns), 5.6 mW/channel power consumption and resistance to temperature and age effects. The isolation barrier time-dependant device breakdown (TDDB) is in excess of 60 years at the full data transmission speed of 150 Mbps, worst case operating temperature and maximum VDD. Silicon Laboratories, Inc. Rev 1.0 1 • The Use of a High-Frequency Carrier Instead of Light The use of a high-frequency carrier further enables low operating power and high-speed operation and adds the benefits of precise frequency discrimination for higher noise rejection and simplified packaging compared to optocouplers. • The Use of a Fully Differential Isolation Path Instead of Single-Ended The differential signal path and high receiver selectivity provides high rejection of common-mode transients (CMTI > 25 kV/µs), external RF field immunity to 300 V/m and magnetic field immunity beyond 1000 A/m for error-free operation. • The Use of Proprietary Design Techniques to Suppress EMI Devices in this family meet the emission standards of FCC Part B and are tested using automotive J1750 (CISPR) test methods. For more information on CMOS isolator emissions, susceptibility and reliability vs. optocouplers, see Silicon Labs white paper “CMOS Isolators Supersede Optocouplers in Industrial Applications” available at www.silabs.com/isolation. CMOS isolator operation is straightforward; an isolator channel (Figure 1) consists of a two-die structure in which the transmitter and receiver are separated by a differential capacitive isolation barrier. Logic high at the isolator input turns the transmitter on, sending a carrier across the isolation barrier to the receiver, which asserts logic high at the output when sufficient in-band carrier energy is detected. Conversely, logic low at the input inhibits transmitter operation, causing the receiver to drive the output low. ISOdriver Channel Die #1 VDD Die #2 ISOLATION IN INPUT CONDITIONING + + - - XMITTER RECVR DRIVER DIFFERENTIAL ISOLATION BARRIER OUT GND Figure 1. CMOS Isolator Top-Level Block Diagram Silicon Labs CMOS isolators can service most applications currently served by digital optocouplers. Like optocouplers, CMOS isolators can be used for safely isolation, voltage level shifting and ground noise mitigation. Consumer appliances using variable-speed, three-phase motors represent a significant opportunity for CMOS isolators. Specialized devices, such as high-speed isolated drivers (“ISOdrivers”), isolated inductive current sensors and multi-channel digital isolators (up to six channels per package) provide high performance, low external BOM, high reliability and competitive cost for many applications. Silicon Laboratories, Inc. Rev 1.0 2 Isolation in Consumer Motor Control Applications There are many areas of the home that require the use of small three-phase motors. In addition to appliances, such as washers and dryers, there are other areas, such as heating and air conditioning systems, air movers (fans, exhaust blowers) and pool pumps that require controls of one form or another. Table 1 lists the more common end applications. Table 1. Home Appliances TYPICAL APPLIANCE MOTOR APPLICATIONS - Adjustable Bed - Air-Conditioner Blower/Compressor - Attic Ventilator - Ceiling Fan - De-Humidifier - Dishwasher - Dryer - Electric Tools (Saw, Grinder, Sander, Compressor) - Exhaust Fan - Freezer - Garage Door Opener - Garbage Disposal - Heater Blower - Humidifier - Jet Pump - Pool Pump - Portable Electric Heater - Refrigerator Fan/Compressor - Sump Pump - Trash Compactor - Treadmill - Washer Motors used in home appliance applications are typically fractional or low-horsepower types with power ratings from 0.25 hp (186 W) to 3 hp (2,238W). While safety certification agencies mandate the use of isolators to protect consumers, isolators are also used in these systems for signal level shifting and electrical noise (ground loop) reduction. SYSTEM CONTROLLER CONTROL INTERFACE ISOLATION PROTECTION & CONTROL RECTIFIER & INVERTER ISOLATED BIAS SUPPLIES BIAS SUPPLIES ISOLATED GATE DRIVERS ISOLATED CURRENT SENSOR MOTOR ISOLATED CURRENT SENSOR POWER SUPPLIES ISOLATED GATE DRIVERS ISOLATED CURRENT SENSOR ISOLATED CURRENT SENSOR 120/240VAC LINE Figure 2. Appliance Motor Control Top-Level Block Diagram Silicon Laboratories, Inc. Rev 1.0 3 Figure 2 is a typical three-phase home appliance motor control system block diagram showing where galvanic isolation is used. Some systems include isolated and/or non-isolated power supplies to provide bias or to provide high-voltage dc to the switching circuits. These supplies typically require isolated gate drivers and/or high-frequency current sensors for current limit protection and/or feedback control. The system may use a small microcontroller for system management, which is powered from an isolated supply. This controller requires isolation to protect against voltage surges into low-voltage areas exposed to the user. The rectifier and inverter together convert the line-derived dc input into ac, which, ultimately, drives the threephase electric motor. These circuits require both safety isolation and level shifting to drive switches riding on high common-mode voltages. Power stage circuits like these typically require isolated gate drivers and current sensors. Isolated Gate Drivers A three-phase motor usually has three high-side/low-side IGBT transistor pairs plus one motor brake IGBT for a total of seven isolated driver channels. At a minimum, IGBT isolated gate drive motor applications require competitive installed cost, high peak output drive, high reliability over elevated temperature conditions and high CMTI. Fast propagation delay times may also be required for fractional-horsepower applications having a high modulation frequency. The three most popular isolated gate drive options are: 1) a single-package optocoupler plus driver (i.e. “optodriver”), 2) a two-chip solution consisting of an optocoupler and an external high-voltage driver IC, or 3) a gate drive transformer circuit. Optocoupler-based drivers exhibit performance and reliability deficiencies regardless of how they are implemented. For example, low CMTI remains an issue that can be addressed with additional external circuitry, but these circuits tend to overdrive the optocoupler, reducing service life. Optodrivers, such as the Avago HCPL-3120, are essentially optocouplers with a higher drive output buffer forming a single-package isolated gate driver. Heat dissipated by the internal driver is easily transferred to the optocoupler, degrading performance and contributing to shorter service life. The two-chip solution (optocoupler plus external HVIC driver) externalizes the driver and improves optocoupler reliability but at an increased cost. Many designers choose lower cost gate drive transformer-based isolated driver solutions because they provide more uniform timing than optocouplers and at lower cost. However, a transformer-based drive topology cannot transmit dc or low frequency and, therefore, imposes maximum duty cycle and ON-time limitations. In addition, they require additional external reset circuitry or a dc blocking capacitor to prevent transformer core saturation. These timing restrictions and added reset BOM overhead make gate drive transformers most useful in systems operating with maximum duty cycles of 50% or less and/or relatively short ON-times. The Si823x ISOdriver is an integrated CMOS multi-channel isolator with on-chip output gate driver circuit that offers higher reliability, substantial timing improvements and higher CMTI compared to optocouplers. It also has no timing restrictions like gate drive transformer designs. These devices are offered in three base configurations: a high-side/low-side isolated driver with separate control inputs for each output (Figure 3a), a single PWM input (Figure 3b) or a dual isolated driver (Figure 3c). Silicon Laboratories, Inc. Rev 1.0 4 VDDI VDDI ISOLATION LPWM VOA UVLO VOA UVLO GNDA VDD1 ISOLATION DISABLE VDD1 VDDI VDDB UVLO UVLO VOB DISABLE GNDB VDD1 VDDB VDDI UVLO GNDA VDDI VDDI ISOLATION VDDI UVLO STEERING LOGIC & DT CONTROL DT VDDI VOA UVLO GNDA DT CONTROL & OVERLAP PROTECTION DT VDDA VIA VOB DISABLE UVLO VOB UVLO GNDB GNDB LPWM VDDB ISOLATION ISOLATION VDDI VDDA PWM ISOLATION VDDA VIA VIB GND VIB GND GND Dual ISOdriver HS/LS PWM Input ISOdriver HS/LS Two Wire Input ISOdriver A) Two-Wire Input High-Side/Low-Side B) One Wire (PWM) Input High-Side/Low-Side C) Dual ISOdriver Figure 3. ISOdriver Family All devices are offered with 0.5 A and 4.0 A peak output current options and isolation ratings of 1 kV, 2.5 kV and 5 kV. The high-side/low-side versions have built-in overlap protection and an integrated adjustable dead time generator. The dual ISOdriver version has no overlap protection or dead time generator. M +HV Isolated VDDA Isolated VDDA VIB GNDI VIA Isolated VDDB DISABLE VDDB VIB GNDI VIA Isolated VDDB DISABLE VDDB VOA GNDA Isolated VDDB DISABLE VIB VDDB DT VOB VOB RDT VOA GNDA DT DT OUT 5V Control Control VOA GNDA Control Control VIA GND VDDI 5V GNDI VDD2 VDDA VDDI VDDI 5V IN Si823x VDDA VDDA Si822x Isolated VDDA Si823x Si823x VOB RDT RDT GNDB GNDB GNDB GND2 -HV Dynamic Brake Inverter Stages Figure 4. Three-Phase Motor Control Power Stage Figure 4 shows an example three-phase ac motor drive for home appliances in which each IGBT pair is driven by a high-side/low-side ISOdriver. The DT input of each driver determines the amount of dead time added between switching phases and can be adjusted over a 4 to 950 ns range with an external resistor to ground. (If dead time is not used, DT should be connected to VDD). The dynamic brake is driven by a single-channel Si822x ISOdriver that is available with either a conventional digital input, or an “optocoupler” input that mimics LED behavior. The Si822x is pin-compatible with many standard optocoupler-based optodrivers, including the HCPL3120. Table 2 below compares the attributes of CMOS isolated drivers with those using optocoupler and gate drive technologies. Silicon Laboratories, Inc. Rev 1.0 5 Table 2. Isolated Driver Technology Comparison Si823x ISOdriver Opto + Driver Gate Drive XFMR ADuM Isolated Gate Driver Digital Isolator + Driver Prop Delay (nS) 50 300+ 10 160 ~100 Stability Over Time & Temperature  POOR: Up to 70% prop delay variation in over temp.    External BOM Components 5 17 12 5 8 Reliability  POOR: LED wearout with temp/ageing    Peak IOUT(max) 4 Various Various 0.1 Various Dead Time Generator Built-In - - - - Overlap Protection Built-in - - - - Summary Best Solution Poor performance Bulky, no integrated over temp, poor protection, EMI reliability, high BOM source Low drive strength, liimited choice of isolation ratings Multi-package design, large footprint For more detailed ISOdriver information, please see the Si823x ISOdriver data sheet and the Silicon Labs white paper, “Improving Isolated SMPS, UPS and other Power Systems with CMOS Isolation Products”. Current Sensing Background Switch mode power control requires current measurement at the system modulation frequency for either feedback control (typically in current mode control) or system protection (typically in voltage mode control). Key considerations in choosing a current sensor are installed cost, reliability, performance, and size. Installed cost includes the sensor and surrounding external components. Excessive current can damage a power system or injure users; so, reliability is a paramount concern. Performance includes attributes, such as power loss, measurement accuracy, and input/output latency. Size is important mostly in small power regulator modules for embedded system applications. The most favored current sense solutions tend to be: 1) current-sense transformers (CT’s), 2) Hall-Effect devices and 3) Shunt + differential amplifiers. While there are other, less expensive, “non-intrusive” methods (e.g. DCR current measurement across the output choke and low-side FET VDS sensing), these techniques tend to have very low accuracy (>40% error) and find use only in highly cost-sensitive applications, such as POL modules. As the name implies, a current transformer (CT) induces current flow in the secondary winding circuit when ac current is present in its primary winding. A burden resistor connected across the secondary scales converts the current to a voltage suitable for connection to a control circuit. CTs tend to have relatively high primary series resistances that reduce power efficiency in large systems and high series inductances that worsen ringing. Small CTs tend to have package lead splay problems and other quality issues. Silicon Laboratories, Inc. Rev 1.0 6 Like gate drive transformers, CTs require a core reset to prevent saturation, and these circuits range from simple to complex, depending on the host system (Figure 5). The self-reset circuit is used in relatively simple, low-frequency applications; the CT is reset by reverse current flow through the CT primary or by the blocking action of D1. Forced Reset resets the CT by initiating reverse current flow from VCC through RC during the CT’s negative-going half-cycle. The controlled reset circuit is used in high-frequency and/or high duty cycle applications where the CT is reset by generating a reverse field when no current is flowing through its primary. C1 R1 CT RS SELF- RESET C1 OUTPUT R1 RS OUTPUT D1 VCC VCC RC D1 C1 RS OUTPUT Q1 R1 VREF CT Q2 CURRENT SOURCE CONTROLLER CT FORCED- RESET CONTROLLED RESET Figure 5. Common CT Reset Circuits Hall Effect devices generate a voltage proportional to an applied perpendicular magnetic field and, without physical contact with the current-carrying conductor being sensed, provide intrinsic isolation. This isolation and the ability to measure both ac and dc currents are the chief advantages of Hall Effect current sensors. However, Hall Effect current sensors are easily affected by external magnetic field interference; they have large temperature drift issues and they have offset issues around zero. The output signals of Hall devices tend to be low-amplitude with a poor signal-to-noise ratio, and their device footprint is often prohibitively large. Closed-loop Hall Effect sensors tend to remedy some of these issues, but at a substantially higher price. The shunt plus differential amplifier is the most intuitive current sense solution, in which a differential amplifier measures the voltage drop across the shunt and generates a current waveform proportional to the measured current. The problem with this method is usually excessive power loss in the shunt and/or an overly narrow measurement frequency range. In addition, these devices tend to have low common-mode voltages relegating them to lower voltage applications. Silicon Laboratories, Inc. Rev 1.0 7 Si850x/1x Current Sensor The Si850x/1x (Figure 6) is a CMOS unidirectional ac current sensor having an accuracy of ±5%, a low 1.3 mΩ series resistance for low loss and direct measurement of ac current from 50 kHz to 1 MHz to a maximum of 20 A. Gate Control Timing Current Si850x/1x CHIP (DIE) METAL SLUG RESET LOGIC INTEGRATOR TEMP SENSOR ADC SIGNAL CONDITIONING Output AUTO CALIBRATION LOGIC Figure 6. Si850x/1x Block Diagram This device consists of a metal slug and CMOS die in a 4 x 4 x 1 mm QFN package. (The isolation rating of the QFN package device is 1 kV; devices in 16SOW package are certified to 5 kV.) The slug and on-die pick-up coil form a coupled inductor in which the ac current flowing through the slug induces a voltage proportional to Lmdi/dt into the pick-up coil. An analog integrator performs an integration of this signal over the switching cycle period and generates a real-time voltage representation of the current through the slug. This signal is further conditioned by an on-chip temperature compensator and gain stage, resulting in a 2 V full-scale waveform at the output pin. The on-chip integrator must be reset prior to the start of each current measurement cycle using only local gate control signals for reset and no external components. The integrator reset criterion is simple: Reset must begin after current measurement and end prior to the start of the next current measurement. For rated accuracy, this reset event should last a least 150 ns. (On-chip one-shot allows the user to trade reduced measurement accuracy for shorter reset time. See the Si850x/1X data sheet for details.) On-chip integrator reset logic provides flexibility to allow the sensor to be used with virtually any power system topology (for more information, see application note AN398: “Using Si85xx Current Sensors in Switch-Mode Power Supplies”). The Si850x/1x is offered in two output versions: ping-pong output and single output. The ping-pong output version (Si851x) is targeted for use in topologies where there are two current paths through the power train, such as in a full-bridge. The single output version (Si850x) is applicable to virtually all other power topologies, such as buck, push-pull, etc. Silicon Laboratories, Inc. Rev 1.0 8 Example Si850x/1x Applications Figure 7 shows a phase-shift-modulated full-bridge application using the Si851x operating in “Ping-Pong” output mode, which enables a single Si851x to replace two CTs (typically used to monitor transformer flux balance). Ping-Pong output mode routes current signals from each leg of the bridge to separate output pins. VIN VDD IIN VDD MODE GND OUT1 OUT1 OUT2 OUT2 Si851x PH1 VDD PH2 TRST R1 R2 R3 R4 IOUT PH3 PH4 Q1 Switches Turned ON PH1 Q2 PH2 Si85xx State 1-4 MEASURE 1-2 RESET 2-3 3-4 MEASURE RESET T1 OUT1 Q3 PH3 Q4 PH4 OUT2 Figure 7. Si851x (Ping-Pong Mode) in Phase-Shifted Full Bridge Application Measured current flowing when Q1 and Q4 are on appears on OUT2, and current flowing when Q2 and Q3 are on appears on OUT1. Integrator reset occurs during the current circulation phase (i.e. when Q1 and Q2 are on or when Q3 and Q4 are on). The relatively low-frequency operation of the full bridge allows ample reset time; so, TRST is tied to VDD, causing reset time to be a function of the states of R1-R4. Silicon Laboratories, Inc. Rev 1.0 9 VDD VIN VDD1 VDD2 RTRST IIN TRST R2 R1 OUT1 Si850x IOUT OUT1 GND1 GND2 GND3 PWM PH2 Si85xx State MEASURE 120nS Q1 PH1 OUT1 L VOUT C Q2 PH2 Figure 8. Buck Regulator Figure 8 shows a simple buck regulator application where reset is provided by the low-side switch gate control signal. In this case, a high-frequency, high maximum duty cycle system is assumed with a maximum reset time allowance of 120 ns. In this case, one-shot timing resistor RTRST is installed between the TRST input and ground with a value chosen to provide the 120 ns one-shot period. Note the timing diagram in Figure 8; the rising edge of the PH2 reset provides the oneshot trigger. Table 3 summarizes the Si850x/1x selection by switch mode topology and shows the reset logic equations and setup of the reset and mode pins. Table 3. Recommended Si850x/1x Configurations by Power Topology Power Topology Recommended Part Number Reset Input(s) Required Input States Reset Logic Expression Output Configuration Buck or Boost Si850x R1 R2 = 0, MODE = 1 XOR(R1, R2) Single Output Half Bridge Si850x R1 R2 = 0, MODE = 1 XOR(R1, R2) Single Output Full Bridge Si851x R1, R2, R3, R4 MODE = 0 [R1 & R2] | [R3 & R4] 4-Wire Ping-Pong Mode 2-Switch Forward Si850x R1 R2 = 0, MODE = 1 XOR(R1, R2) Single Output Push-Pull Si851x R1, R2 R3 = 0, R4 = 1 MODE = 1 XNOR [R1, (R2 | R3)] 2-Wire Ping Pong Mode Silicon Laboratories, Inc. Rev 1.0 10 Brushless dc motors (BLDC), also called permanent magnet dc synchronous motors, have rapidly gained popularity because of their desirable characteristics. From a performance perspective, the BLDC behaves like a dc motor with linear relationships between current and torque and voltage and rotational speed. BLDC motors offer advantages over brushed dc motors and induction motors including better speed versus torque characteristics and dynamic response, high efficiency and reliability, long operating life, noiseless operation, higher speed ranges and reduced electromagnetic interference (EMI) emissions. In addition, the ratio of delivered torque to the size of the motor is higher, making it useful in applications where space and weight are critical factors. The BLDC speed controller shown in Figure 9 regulates BLDC speed by varying the average voltage across the motor phases using pulse-width modulation. This single-sided PWM, 120 degree conduction mode, two-quadrant controller approach is simple and capable of driving the motor in both directions. G1 G1 G2 G3 G5 M VDC G3 G4 G4 BLDC Speed Sensor G2 G6 G5 G6 Q2 Q4 Q6 74HC4002 Controller Position Sensing Q1 Q2 Q3 Q4 Q5 Q6 ISOdriver Isolated Gate Drivers Rotor Sensor Inputs Q1 Q2 Q3 Q4 Q5 Q6 PWM Q SET 5V VDD MODE R2 Si850x AC Current Sensor GND PWM OSC 2 Quadrant Commentator (Firmware) IIN R1 IOUT OUT S Vcp Q CLR Speed Command R DIR Direction Control Q VDD D CLK Overcurrent Detector VREF Q Direction VREF Figure 9. BLDC Feedback Speed Control Using Si850x AC Current Sensor and Si8xxx ISOdrivers Silicon Laboratories, Inc. Rev 1.0 11 Figure 10. 120 Degree Motor Commutation Timing Diagram The voltage switching scheme is simple as well; only two of the six switches are on at any time, alternately switching the voltage to motor phases. The voltage waveforms for all six gates of the Figure 9 controller are shown in Figure 10 (the gate voltage timing sequence is: G1 and G2, G2 and G3, G3 and G4, G4 and G5, G5 and G6, G6 and G1). As shown in Figure 9, the Si850x ac current sensor can be used to sense current in each BLDC motor phase. The required modulation frequency for the controller in Figure 9 is less than 70 kHz, and the maximum PWM duty cycle can be clamped to a maximum of 80%, allowing a more than ample amount of time to perform the cycle-by-cycle Si850x reset. Figure 12 shows a simplified feedback torque controller that is only a slight variation of the speed controller shown in Figure 9. PWM Gate Drive Si850x Output Waveform Si850x Reset Period Figure 11. Reset Timing for Si851x AC Current Sensor Silicon Laboratories, Inc. Rev 1.0 12 G1 G1 G2 G3 G5 M VDC G3 G4 G4 BLDC G2 G6 G5 G6 Q2 Q4 Q6 74HC4002 Controller Position Sensing Q1 Q2 Q3 Q4 Q5 Q6 ISOdriver Isolated Gate Drivers Rotor Sensor Inputs Q2 Q4 Q5 VDD MODE Si850x AC Current Sensor Q1 Q3 IIN R1 2 Quadrant Commentator (Firmware) Q6 Q SET IOUT OUT S Gain Amplifier CLK Q CLR Speed Sensor GND PWM OSC PWM 5V R DIR Direction Control Q VDD D Torque Command CLK Q Direction VREF Minimum Speed Figure 12. Torque Control Using the Si850x AC Current Sensor and Si823x ISOdrivers Extending Si850x/1x Full Scale Range AC current measurements beyond 20 A can be realized using the circuit board layout modification shown in Figure 10. The image on the left is an “X-ray view” of the Si850x/1x mounted on a circuit board, where all of the current flows through the slug. The image on the right adds a small current bypass trace in parallel with the slug, forming a current divider where the width and thickness of the bypass trace determine the current divider ratio. For example, a 1 mm wide trace shunts enough current around the slug to increase Si85xx full-scale 1.8 times to 36 A. (For more information on extending Si850x/1x range, please see application note AN329: “Extending the Full-Scale Range of the Si85xx” .) Note also that the Si850x/1x can be over ranged up to 50% with no damage and without the bypass trace shown in Figure 10. A 50% over range causes the output voltage to rise to 3 V instead of 2 V. See the Si850x/1x data sheet for more details. Silicon Laboratories, Inc. Rev 1.0 13 CONDUCTOR Si85xx CURRENT BYPASS Si85xx SLUG SLUG Figure 10. Extending Full Scale Range Using Current Bypass Trace Summary There are many areas of the home that require the use of small three-phase motors, including washers, dryers, heating and air conditioning systems and more. These end applications frequently require galvanic isolation for safety, ground noise mitigation and/or voltage level shifting. Legacy technologies, such as optocouplers and Hall effect current sensors, have traditionally been used for such applications. Silicon Labs CMOS isolation technology has given rise to isolated gate drivers, multi-channel digital isolators and ac current sensors that offer higher capability and significant gains in performance and reliability compared to legacy devices. Silicon Laboratories, Inc. Rev 1.0 14 Related Documents 1. Silicon Labs application note AN441: “Using the Si8232/5/6 Dual ISOdrivers in Power Delivery Systems” 2. Silicon Labs application note AN486: “High-Side Bootstrap Design Using Si823x ISOdrivers in Power Delivery Systems” 3. Silicon Labs application note AN490: “Using ISOdrivers in Isolated SMPS, UPS, AC Inverter and Other Power Systems.” 4. Silicon Labs application note AN497: “Adding Overcurrent Protection to ISOdrivers” 5. Silicon Labs application note AN583: “Safety Considerations and Layout Recommendations for Digital Isolators” 6. Silicon Labs white paper: CMOS Digital Isolators_WP.pdf; Title: “CMOS Digital Isolators Supersede Optocouplers in Industrial Applications” Silicon Laboratories, Inc. Rev 1.0 15