Improving Isolated SMPS, UPS and other Power Systems with CMOS Isolation Products Fully-integrated isolated gate drivers and PMBus communication interfaces can significantly increase efficiency, performance and reliability compared to legacy solutions Introduction: As today’s emerging “green” energy standards challenge designers to deliver systems with increased power efficiency and system reliability while decreasing cost and size, the need for more highly-integrated power components becomes increasingly important. Isolated gate drivers and digital isolators are critical building blocks within today’s ac-dc and isolated dc-dc power supplies. This paper describes how SMPS, UPS and other similar power system designers can improve their products by adopting fully-integrated isolation solutions from Silicon Labs. Rectifier PFC PRIMARY 400VDC VIN SECONDARY FULL BRIDGE TOPOLOGY Local VDD Q1 I1 HIGH SIDE DRIVER Q3 Q4 XFMR PRIMARY LOW SIDE DRIVER AC LINE IN Q2 LOW SIDE DRIVER Q6 OUTPUT VS XFMR SECONDARY VS HIGH SIDE DRIVER SYNCHRONOUS RECTIFIERS I2 ISOLATION BARRIER SMPS Controller Q5 AC CURRENT SENSOR AC CURRENT SENSOR ISOLATED DRIVER ISOLATED DRIVER FEEDBACK ISOLATION PMBus ISOLATION 4 PMBus or I2C Interface Figure 1: AC/DC Converter Using Full Bridge Topology Silicon Laboratories, Inc. 1 Example System: Isolated power converters require power stage and signal isolation to meet safety standards. The example of Figure 1 shows an ac-dc converter typical of 500 W to 5 kW power systems, such as those used in central office telecom rectifier supplies. The first stage of this two-stage system is a power factor correction circuit (PFC) that increases system efficiency by forcing the ac line current to be in-phase with the line voltage (i.e. purely resistive load). The resulting 400 VDC PFC output voltage is supplied to the second stage isolated PWM full-bridge dc/dc converter that converts the input to a lower value useable by the end application (e.g. 72 V). The full bridge operates by alternately turning corner switch pairs Q1, Q2 and Q3, Q4 on and off, causing alternating current to flow through the transformer primary (I1 and I2 current in Figure 1). This results in an ac waveform at the transformer secondary, which is then converted to dc by synchronous rectifier switches Q5 and Q6. The primary-side high-side switch driver inputs in Figure 1 are referenced to the primary-side ground while the driver outputs are referenced to the high-side MOSFET source pins. The high-side drivers must, therefore, be able to withstand the 400 VDC common-mode voltage present at the source pin during highside drive. The corresponding low-side drivers operate from a low-voltage local supply (e.g. 18 V) and referenced to the primary-side ground. Note also the two ac current sensors in the low-side legs of the bridge that monitor the current in each leg to facilitate flux balancing if voltage mode control is used. The isolation barrier of Figure 1 ensures no current flow between the primary and secondary-side grounds; consequently, the drivers for synchronous MOSFETs Q5 and Q6 must be isolated. The secondary-side 2 feedback path (and PMBus or I C communication interface, if used) must also be isolated for the same reason. While optocouplers are commonly used for feedback isolation, they are not fast enough for use in the synchronous MOSFET gate drive isolation circuit. While faster optocouplers are available, they tend to be expensive and exhibit performance and reliability liabilities typical of optocouplers, such as loss of performance over temperature and device age. For example, published opto-coupler and opto-driver failure rates (FITs) are typically 10 times higher than couplers based on CMOS technology. As a result, gate drive transformers have become popular in isolated synchronous rectifier applications. Advancements in CMOS-based (Complementary Metallic Oxide Semiconductor) isolation technology make possible isolators having near-ideal performance, power, integration and reliability characteristics. These devices are well positioned to supersede both optocouplers and gate drive transformers in switch mode power applications. For a more detailed comparison between ISOpro and optocouplers, see Silicon Labs white paper: “ISOpro RF Isolators Supersede Optocouplers in Industrial Applications”. Silicon Laboratories, Inc. 2 ISOpro Technology Overview ISOpro is an RF carrier-based isolation technology fabricated in main-stream CMOS, supplied in standard IC packaging and offered in 1 kV, 2.5 kV and 5 kV isolation ratings. This technology offers uniform, stable performance over operating voltage and temperature with none of the fundamental weaknesses of optocouplers. A block diagram of an ISOpro isolator channel is shown in Figure 2a. ISOdriver Channel Die #1 VDD Die #2 ISOLATION IN INPUT CONDITIONING + + - - XMITTER RECVR DIFFERENTIAL ISOLATION BARRIER DRIVER Input Die Output Die OUT GND Input Pin RF ENERGY Transmitter Output RF ENERGY Receiver Input Output Pin a) Block Diagram b) Decapsulated Die Photo Figure 2: ISOpro Isolator The operation of the ISOpro is analogous to that of an optocoupler, except an RF carrier is used instead of light. ISOpro isolators consist of two identical semiconductor dies in a standard IC package where each die contains both transmit and receive circuits. When wire-bonded together (Figure 2b), the two die form an RF transmitter and receiver separated by a differential capacitive isolation barrier. Data is transferred from input to output by simple on/off keying (OOK) modulation, i.e. when an input pin (VIN) is high, the transmitter generates an RF carrier that propagates across the isolation barrier to the receiver. The receiver asserts logic 1 on the output pin (VOUT) when sufficient in-band carrier energy is detected. When VIN is low, the transmitter is off, and the receiver drives VOUT low because no in-band RF energy is detected. This deceptively simple architecture offers significant benefits compared to other isolation schemes, including: • Greater operating stability over supply voltage, temperature and device age • Wider operating range: -40 to +125 °C • Significantly lower power consumption • Tighter timing characteristics for more consistent end-system performance • Significantly higher speed data transmission • Higher reliability (mainstream CMOS process technology) • Higher common-mode transient immunity (CMTI) • High RF and magnetic field immunity • Significantly higher device integration (up to 6 channels per package) • Low EMI - meets FCC Class B Part 15 • Highly competitive price per channel Silicon Laboratories, Inc. 3 ISOpro vs. Gate Drive Transformers: Gate drive transformers (Figure 3) are miniature torroidal transformers that are preferred over optocouplers in gate drive applications because of their shorter delay times. While they are faster than optocouplers, gate drive transformers cannot propagate a dc level; they can pass only a finite voltagetime product across the isolation boundary. These transformers must be reset after each ON cycle to avoid core saturation (requiring external circuitry) and restrict both tON and duty cycle range, which compromise transient load performance. +5V -5V 10V 0 Basic Circuit + - - + DC Restore a) Typical Gate Drive Transformer b) Gate Drive Transformer Circuits Figure 3: Gate Drive Transformers A basic transformer-isolated gate drive circuit (Figure 3b) places a dc blocking capacitor in series with the gate drive transformer. During operation, a dc bias develops across the blocking capacitor in an amount equal to the gate drive voltage amplitude multiplied by the duty cycle (VBC = VDRIVE x D). As a result, this scheme is not practical for designs requiring duty cycles greater than 50% because the peak output amplitude decreases as duty cycle increases. Also, the duty cycle-dependant bias changes across the coupling capacitor can ring with the transformer magnetizing inductance in an amount sufficient to turnon the MOSFET periodically. Compensating for this issue by increasing the blocking capacitor value and/or gate resistance or slowing down duty cycle rate of change can help, but too large a capacitor value can cause the transformer to saturate during transients. The bottom graphic of Figure 3b shows a dc restored isolated gate drive circuit in which the secondary side diode and capacitor restores the dc value of the gate drive, allowing operation at duty cycles beyond 50%. While higher duty cycles are supported, this circuit suffers from the same ringing and possible transformer saturation problems previously described. In addition, during extended off times, the charged primary side capacitor is connected directly across the transformer primary where it can saturate the transformer. In this case, the transformer secondary becomes a short circuit, enabling the secondary side capacitor to inadvertently turn-on the MOSFET. In summary, the transformer-isolated gate drive design is best suited for systems having duty cycles of 50% or less. However, applications like the one shown in Figure 1 typically require a maximum duty cycle well over 50%. For such applications, transformer isolation will require the dc restore circuit (bottom graphic, Figure 3b), and its potential pitfalls. The transformer-based design will also have lower efficiency and higher EMI (and lower/worse transient load performance) and will occupy more board space than the ISOpro-based solution. Silicon Laboratories, Inc. 4 ISOpro-Based Solutions As of the publication date of this paper, ISOpro-based technology addresses isolated gate drive and PMBus isolation for the example power system of Figure 1. ISOdrivers combine ISOpro isolation technology with gate driver circuits to create integrated, low-latency isolated driver solutions for MOSFET and IGBT applications. ISOdrivers are available in three basic configurations (Figure 4): high-side/low-side isolated drivers with separate control inputs for each output (Figure 4a) or a single PWM input (Figure 4b), and dual isolated drivers (Figure 4c). All devices are available in 0.5 A and 4.0 A peak output current and all are available in 1 kV, 2.5 kV and 5 kV isolation ratings. The high-side/low-side versions have built-in overlap protection and an adjustable dead time generator, while the dual ISOdriver version has no overlap protection or dead time generator. As such, the dual ISOdriver variants can be used as dual lowside, dual high-side, or high-side/low-side isolated drivers. The single-channel Si822x series ISOdrivers feature an input circuit that mimics that of an optocoupler. These devices directly replace legacy optodrivers, and provide substantial gains in performance, power and reliability. VDDI VDDI ISOLATION UVLO VDD1 VDDI VDDB UVLO DISABLE ISOLATION VDDI GNDA VDDI VDDI VDD1 UVLO VDDB VDDI UVLO VOB UVLO GNDB VOA UVLO GNDA STEERING LOGIC & DT CONTROL DT DISABLE ISOLATION VDDI VIA VOA UVLO GNDA DT CONTROL & OVERLAP PROTECTION DT VDDA VOB VDD1 VDDB ISOLATION ISOLATION LPWM VOA VDDI VDDA PWM ISOLATION VDDA VIA DISABLE UVLO VOB UVLO GNDB GNDB VIB LPWM GND VIB GND GND HS/LS Two Wire Input ISOdriver HS/LS PWM Input ISOdriver a) Two-Wire Input High-Side/Low-Side b) One Wire (PWM) Input High-Side/Low-Side Dual ISOdriver c) Dual ISOdriver Figure 4: ISOdriver Family These devices are based on a 3-die architecture that enables drive channels to be isolated from each other as well as from the input side. This allows the polarity of the high-side and low-side channel to reverse without latch-up or other damage, a critical system safety and reliability consideration for power systems and motor control/drives. Output Die Input Die Output Die Figure 5: Decapsulated ISOdriver Silicon Laboratories, Inc. 5 Low Side Driver Selection: Among other considerations, system voltage, output power and efficiency requirements drive the selection of the system switching MOSFETs, which, in turn, drive the selection of the gate driver. Power MOSFET selection is made by extracting the key operating parameters from the system specification, then finding the most cost-effective MOSFET that can meet the requirements as demonstrated by Design Example 1. Design Example 1: Select an ISOdriver to drive the secondary-side full-wave synchronous MOSFETs of Figure 1, assuming a system output voltage of 12 VDC, and switch rise and fall times of 35 ns, and a MOSFET input capacitance (Ciss) of 5,180 pF. Assume VGS = 12 V for full enhancement. Solution: Referring to Figure 1, the output-side MOSFETs have grounded source terminals; so, 12 V gate drive will be applied from the MOSFET gate to ground. As a result, the MOSFET gates can be driven with an isolated dual low-side driver (i.e. Si8235/6), and the peak current is calculated by first determining the required gate charge (QG) to fully enhance the MOSFET, then dividing QG by the required rise time as shown in Equations 1 and 2: QG = ∆ VGS * Ciss (Equation1 ) Where ∆ VGS is the gate-to-source voltage -12 = 12 * 5,180 x 10 = 62nC IPK = QG tR (Equation 2) = 62 x 10-9 -9 35 x 10 = 1.8A While the calculated peak drive current is 1.8 A, the specified 12 V gate drive voltage must be taken into account in driver selection. For example, a driver specified at 2 A at 18 V will produce a lower peak output current at a supply voltage of 12 V. The ISOdriver has a 2 A peak sourcing current output at VDD = 12 V, which is perfect for this application. The ISOdriver application diagram for Design Example 1 is shown in Figure 6. Note that the bypass capacitors on the Si823x should be located as close to the chip as possible; the recommended VDD bypass circuit is a 0.1 µF capacitor in parallel with either a 1 μF or 10 μF bypass capacitor (depending on peak current requirements). Note that resistors R1 and R2 are usually added to minimize ringing, while diodes D1 and D2 provide fast turn-off to prevent transformer reverse current flow. Silicon Laboratories, Inc. 6 12V 5V C3 0.1uF C2 1uF GND SYNCHRONOUS RECTIFIERS GNDA Si8235/6 VIA From Controller C4 10uF Q6 XFMR SECONDARY C1 0.1uF VDDA 12V OUTPUT VDDI VDDB C3 0.1uF VIB C4 10uF DISABLE Q5 D1 GNDB VOA R2 VOB R1 D2 Figure 6: Secondary-Side Isolated Driver Figure 6 is checked for operation within safe thermal limits across the entire load range using Equation 3. Note that FPWM = 200 kHz, and the input MOSFET input capacitance (CL) is 5,180 pF: PD = VDDI IDDI + 2(VDDO IQOUT + CINTVDDO2F) + 2n(CLVDDO2F) (Equation 3) where: PD is the total ISOdriver device power dissipation (W) IDDI is the input-side maximum bias current (3 mA) IQOUT is the driver die maximum bias current (2.5 mA) Cint is the internal parasitic capacitance (75 pF for the 0.5 A driver and 370 pF for the 4.0 A driver) CL is the load capacitance VDDI is the input-side VDD supply voltage (4.5 to 5.5 V) VDDO is the driver-side supply voltage (10 to 24 V) F is the switching frequency (Hz) n is the overlap constant (max value = 2) -3 -3 -12 2 3 -12 2 3 PD = 5(3 x 10 ) + 2(12 x 2.5 x 10 + 370 x 10 x 12 x 200 x 10 ) + 2(5,180e x 12 x 200 x 10 ) = 96 mW -3 ISOdriver operating temperature: 16SOW θja = (100 °C/W) x 96 x 10 + 25 °C ambient = 34 °C. 34 °C is well within the extended temperature range of -40 to 125 °C of the Si8235/6. Silicon Laboratories, Inc. 7 High-Side Driver Considerations: Because ISOdriver output channels are isolated from the input and from each other (see Figure 5), they exhibit less channel-to-channel capacitive coupling, and higher output-side dV/dt immunity compared to the non-isolated, high-voltage drivers of Figure 1. Like the high-voltage driver, the ISOdriver requires a high-side bootstrap circuit to provide bias and gate voltage drive current during the high-side switch cycle. Capacitor CB (Figure 7) charges during the low-side drive period (i.e. when Q2 is on and Q1 off). During this time, charge current flows from VDD into both the ISOdriver VDDA input and into bootstrap CB. At the end of the low-side drive period, Q2 is turned off, and Q1 is turned on causing its source terminal to quickly rise toward VIN. This action reverse biases bootstrap diode D1 and disconnects the ground-based VDD supply from CB. Since the low side of CB is referenced to the MOSFET source (GNDA), Q1 VGS will be approximately VDD – 0.7V, thereby holding Q1 in its active state. From this point until the end of the highside drive period, CB supplies all of the current required to maintain high-side driver operation. RB D1 D1 VDD Cm1 VDDA VDRAIN Cm1 VDDA Q1 OUTA GNDA RB VDRAIN VDD CB CB Vgs GNDA CB Charge Path Vgs CB Charge Path Cm2 Cm2 VDDB VDDB OUTB Q1 OUTA Q2 OUTB Q2 GNDB GNDB a) Bootstrap Circuit – CB Charging b) Bootstrap Circuit – CB Sourcing Figure 7: Bootstrap Operation Proper bootstrap design will take into account the total charge required to fully enhance the high-side MOSFET plus the bias current to support the high-side driver VDD. Other design considerations include minimizing the ripple on bootstrap capacitor CB and providing additional current to offset leakage. These considerations coalesce into a total charge CB requirement, which, in turn, drives the value of CB and charge current. Bootstrap design is covered in detail in Silicon Labs application note “AN486: High-Side Bootstrap Design Using Si823x ISODrivers in Power Delivery Systems.” Silicon Laboratories, Inc. 8 Maximizing System Efficiency: High-side/low-side drive must have a “break-before-make” execution to avoid efficiency-robbing shootthrough currents caused by both MOSFETs being on at the same time. While high-side/low-side ISOdrivers have overlap protection that disables the outputs when both inputs are high, downstream delays in power train can still cause shoot through. The time period between switch transitions where both switches are off is referred to as “dead time” (Figure 8b). Must avoid shootthrough current (Q1, Q2 on simultaneously) Q1 A IOUT = 10A OUTA VOUT Q2 power loss when ON = IOUT2 x RDSON = 0.5W Q2 OUTB Q2 Power loss when OFF = VT x IOUT = 7W B Dead Time BODY DIODE (VT) a) Shoot-Through Current b) Dead Time Figure 8. Dead Time A small amount of dead time can increase system efficiency, but larger amounts reduce efficiency as shown in Figure 8a. The power dissipated by Q2 while on is 0.5 W (10 A through Q2 RDSON of 5 mΩ), but this increases to 7 W (0.7 V x 10 A) when current flows through the Q2 body diode. Given this, the amount of dead time added to the system timing must be only large enough to prevent shoot-through current. OVERLAP OVERLAP VOB VIA VIA 50% VIB VIB DT DT DT DT 90% VOA VOA 10% DT DT 90% VOB VOB 10% a) Normal Dead Time Behavior b) Dead Time Behavior During Overlap Figure 9. ISOdriver Dead Time Behavior High-side/low-side ISOdrivers have an integrated dead time generator that can be set from 4 ns to 950 µs using an external resistor to ground. Figure 9a shows the timing behavior of the dead time generator in normal operation. Note that the VIA, VIB timing waveforms are aligned, and dead time is automatically added on both the rising and falling edges. Note also that overlap protection overrides dead time in the event that both ISOdriver inputs are high at the same time (Figure 9b). A well-designed configurable power delivery system using ISOdrivers’ dead-time control feature can, theoretically, increase overall system efficiency (η) by 4%. Silicon Laboratories, Inc. 9 Dual ISOdrivers: While dead time optimization can increase efficiency up to 4%, additional efficiency gains may be possible by paralleling MOSFETs or increasing gate drive to a single, larger MOSFET. In either case, the dual ISOdriver is useful in providing additional drive capability. Unlike the dedicated high-side/low-side ISOdrivers, the Si8232/5/6 Dual ISOdrivers do not have overlap protection or a dead time generator; so, its output unconditionally follows that of the input as long as the device is powered. Like all ISOdrivers, the two driver output circuits are isolated from each other, allowing the common-mode voltage between the two channels to reverse polarity without damaging or upsetting the device (Figure 10). 5V VDDA Si8232/5/6 VOA GNDI OUT A GNDA GNDA VIA VDDB From Controller VDDB VIB VOB Output Signal VOA Output Signal VDDA Common Mode Voltage (V) VDDI VOB OUT B VOB GNDB DISABLE Common Mode Voltage V1 VOB Output Signal VOA Output Signal Common Mode Voltage V2 Time Figure 10: Common Mode Voltage Inversion Many power applications, such as UPS systems and inverters, require added drive for parallel switch pairs. The combined capacitive loading of these switches requires either a higher peak current driver or a less desirable method of distributing the switches over multiple gate driver ICs. The circuit of Figure 11 shows each Si8232/5/6 output driving several common ground switches in parallel. When connected in this way, the dual ISOdriver can provide an equivalent peak drive current of 8 A while 50 ns propagation delay time ensures that all switches are driven off and on simultaneously. Isolated 24VDC LOAD VDDI 5V Si8232/5/6 VDDI VDDA VOA GNDA GNDI From Controller VIA VDDB GNDB VIB VOB DISABLE Figure 11 Paralleled Outputs for Increased Peak Output Current Power circuits in high-voltage systems, such as imaging systems and plasma flat panels, have split ground systems to isolate higher voltages from lower voltages. In many cases, local supply regulators are built using a dedicated controller for each regulator or, in other cases, a transformer-coupled multi-output design (using flyback or other transformer-coupled topology). Figure 12 shows a dual output isolated buck converter using the Si8232/5/6 dual ISOdriver. As shown, a single two-loop controller is used with the ISOdriver to generate two stepped-down output voltages. Silicon Laboratories, Inc. 10 The ISOdriver in Figure 12 operates as an isolated dual high-side driver where each output is isolated from both the adjacent output and from the primary side. While this circuit uses a low-cost Schottkey freewheeling diode, a second dual ISOdriver can be added to control output synchronous rectifiers for higher efficiency. Isolated V1 VDDA 5V HV Si8232/5/6 VDDI VDDA VOA VOUT 1 GNDA Isolated V2 GNDI TWO-LOOP CONTROLLER OUT1 LV VIA VDDB OUT2 VIB VOB GNDB I/O VFB1 VOUT 2 DISABLE ANALOG SIGNAL ISOLATION VFB2 Figure 12: Dual Isolated Buck Converter in Plasma or Imaging System Isolating PMBus PMBus is a popular communications interface for networked power system architectures and uses 2 SMBus/I C as its physical interface. Most power systems place the PMBus transceiver function on the secondary-side of the system, often implemented with a small microcontroller and support circuitry. 2 However, as the Industry trends toward digital control, the I C interface is often located on the primary2 side controller and requires isolation for secondary-side connection. Adding galvanic isolation to the I C interface is difficult because the two communication signals (SDA, SCL) are bidirectional. At first glance, it appears that SDA and SCL can be isolated by simply placing two optocouplers in parallel and in opposite directions. However, this technique creates feedback that latches the bus line low when a logic low is asserted by either master or slave. As a result, additional anti-latch circuits must be added to the design making the discrete optocoupler approach bulky and slow. Silicon Laboratories, Inc. 11 Figure 13: I2C Isolator: Si8400/05 versus Discrete Optocoupler Circuit 2 The Si8400/05 I C isolators integrate isolator and anti-latch functions into a single package and provide isolation to a maximum of 2.5 kVACRMS. Since the SCL pin is bidirectional, these products support clock 2 stretching and operate to a maximum bus speed of 1.7 Mbps. A complete I C isolation solution can contain up to two bidirectional lines (SDA, SCL) and two isolated unidirectional signal lines for reset and 2 interrupt functions. Figure 13 compares the size and complexity of a discrete optocoupler I C isolator 2 implementation (top graphic) with that of the Si8400/05 (note the 300 mm area required by the 2 optocoupler solution does not account for the area occupied by the anti-latch circuits). The 150 mm 2 footprint uses a competitor’s I C isolator but requires a second isolator to supply the extra unidirectional signal isolators. 2 I C Isolator Design Considerations: Without anti-latch protection, both sides of the bidirectional isolators will latch when an isolator output logic low propagates back through an adjacent isolator channel, and anti-latch protection must be added 2 to one side of the isolator to avoid this condition (the "A" side for the Si8400/05). The I C isolator "A side" output low (VOL) and input low (VIL) levels are designed so that the isolator, VOL, is greater than the isolator, VIL (Figure 14). Side A Side B Figure 14: Si8400/05 I2C Anti-Latch Using Level Discrimination Silicon Laboratories, Inc. 12 Ideally, the A side should connect to the bus side that: (1) meets the isolator’s pull-up current specs (0.5 to 3 mA) and (2) has the highest VIL (e.g. some bus devices specify VIL = 0.9 V while others specify VIL = 0.3 x Vdd). Assuming a 3.3 V minimum power supply, the side with VIL = 0.3 x Vdd is the better side because this side has an input low level of 1.0 V) (3) has bus devices that can pull down below the isolator input low level and (4) has the lowest noise. 2 The use of monolithic I C isolators with additional unidirectional channels allows system designers to simplify timing challenges in a design. Instead of being forced to isolate additional status and control channels in multiple isolator or opto-coupler packages (which results in significant part-to-part timing 2 variations), monolithic I C isolators with extra unidirectional channels exhibit timing characteristics that track very closely across process, voltage and temperature variations. The Si8405 has two additional 2 unidirectional channels that are useful for isolating reset and interrupt signals. I C design does not have to be a mystery. By considering each of these design tips and choosing an isolator appropriate to the 2 demands, designers can easily implement I C isolation in their products. Conclusions ISOpro technology offers substantial performance, reliability, integration and per-channel cost advantages over legacy isolation technologies, such as optocouplers and gate drive transformers. The ISOpro-based Si823x and Si822x ISOdrivers are single-chip, isolated gate drivers featuring ultra-fast 50 ns propagation delays for increased timing margins, a dead time generator for higher system efficiency, stable operation over temperature and time and lower BoM costs and PCB footprints. Supporting output power supplies to 24 V and 0.5 or 4.0 A peak output current, ISOdrivers efficiently drive MOSFET and IGBT power stages in high-performance, isolated switch mode power supplies. The high-side/low-side versions have built-in protection against overlap timing errors, ensuring safe and efficient operation. Built-in dead time configurability allows the SMPS designers to tune their system for peak system efficiency. ISOpro-based 2 Si8400/05 I C isolators eliminate secondary-side PMBus communication interface circuitry in networked power system, saving design time, cost and board area. These devices are complete solutions to the 2 problem of isolating the I C interface. The Si840x series operates at data rates useful in networked power 2 systems where the I C interfaces on the primary-side controller operate up to 1.7 Mbps. The Si850x/1x isolated high-frequency ac current sensors offer smaller size, lower power loss, and higher accuracy with reduced external BoM compared to legacy current sensing technologies. All of the ISOpro products have the common thread of high-performance, integration and value and are ideal for meeting the challenges of today’s energy-efficient power delivery systems. Silicon Laboratories, Inc. 13