Circuit Note CN-0196 Devices Connected/Referenced ADuM7234 Isolated Precision Half-Bridge 4 A Driver ADG787 2.5 CMOS Low Power Dual 2:1 Switch Circuits from the Lab reference circuits are engineered and ARM7 Based Microcontroller with Dual tested for quick and easy system integration to help solve todays ADuC7061 analog, mixed-signal, and RF design challenges. For more 24-Bit - ADCs information and/or support, visit www.analog.com/CN0196. ADuM3100 Digital Isolator ADP1720 50 mA Linear Regulator ADCMP350 Comparator with 0.6 V Reference H-Bridge Driver Circuit Using Isolated Half-Bridge Drivers The ADuM7234 is an isolated, half-bridge gate driver that EVALUATION AND DESIGN SUPPORT employs Analog Devices iCoupler technology to provide Circuit Evaluation Boards independent and isolated high-side and low-side outputs CN-0196 Circuit Evaluation Board (EVAL-CN0196-EB1Z) making it possible to use N-channel MOSFETs exclusively in ADuC7061 MiniKit (EVAL-ADuC7061MKZ) the H-bridge. There are several benefits in using N-channel Design and Integration Files MOSFETs: N-channel MOSFETs typically have one third of the Schematics, Layout Files, Bill of Materials on resistance of P-channel MOSFETs and higher maximum CIRCUIT FUNCTION AND BENEFITS current they switch faster, thereby reducing power dissipation The circuit, shown in Figure 1, is an H-bridge composed of high and the rise time and fall time is symmetrical. power switching MOSFETs that are controlled by low voltage The 4 A peak drive current of the ADuM7234 ensures that the logic signals. The circuit provides a convenient interface power MOSFETs can switch on and off very fast, thereby between logic signals and the high power bridge. The bridge minimizing the power dissipation in the H-bridge stage. The uses low cost N-channel power MOSFETs for both the high and maximum drive current of the H-bridge in this circuit can be low sides of the H-bridge. The circuit also provides galvanic up to 85 A, which is limited by the maximum allowable isolation between the control side and power side. This circuit MOSFET current. can be used in motor control, power conversion with embedded The ADuC7061 is a low power, ARM7 based precision analog control interface, lighting, audio amplifiers, and uninterruptable microcontroller with integrated pulse width modulated (PWM) power supplies (UPS). controllers that have outputs that can be configured to drive an Modern microprocessors and microconverters are generally low H-bridge after suitable level translation and conditioning. power and operate on low supply voltages. Source and sink CIRCUIT DESCRIPTION current for 2.5 V CMOS logic outputs ranges from A to mA . Driving an H-bridge switching 12 V with a 4 A peak current Level Translation of 2.5 V PWM Control Signal to 5 V requires the use of carefully selected interface and level The EVAL-ADuC7061MKZ delivers 2.5 V logic level PWM translation components, especially if low jitter is needed. signals, while the minimum logic high input threshold for the The ADG787 is a low voltage CMOS device that contains two ADuM7234 is 3.5V with a 5 V power supply. Because of this independently selectable single-pole double-throw (SPDT) incompatibility, the ADG787 switch is used as an intermediate switches. With a 5 V dc power supply, a voltage as low as 2 V level translator. The minimum input logic high control voltage is a valid high input logic voltage. Therefore, the ADG787 to the ADG787 is 2 V, which is compatible with the 2.5 V logic provides appropriate level translation from the 2.5 V controlling from the ADuC7061. The output of the ADG787 switches signal to the 5 V logic level needed to drive the ADuM7234 between 0 V and 5 V, which is more than sufficient to drive the half-bridge driver. Rev.0 Circuits from the Lab circuits from Analog Devices have been designed and built by Analog Devices engineers. Standard engineering practices have been employed in the design and construction of each circuit, and their function and performance have been tested and verified in a lab environment at room temperature. However, you are solely responsible for testing the circuit and determining its One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. suitability and applicability for your use and application. Accordingly, in no event shall Analog Devices Tel: 781.329.4700 www.analog.com be liable for direct, indirect, special, incidental, consequential or punitive damages due to any cause whatsoever connected to the use of any Circuits from the Lab circuits. (Continued on last page) Fax: 781.461.3113 2011 Analog Devices, Inc. All rights reserved. CN-0196 Circuit Note 12V 5V 5V D1 D2 R1 R2 V NC DDA 1 ADuM7234 16 10 10 C1 C1 + Z2 + V Z1 R5 V OA 330F IA 330F R6 2 ENCODE DECODE 15 13V 100k 13V 25V 25V 100k ADG787 V GND IB A 3 14 S1A 5V V DD1 NC D1 4 13 S1B GND 1 NC 5 12 12V IN1 V DISABLE DDB IN2 6 11 V V DD1 OB S2A 7 ENCODE DECODE 10 D2 Q1 Q2 S2B R7 R9 NC GND B 8 9 15 15 GND D5 D6 V NC DDA 1 ADuM7234 16 V V OA IA ENCODE DECODE 2 15 M V GND IB A 3 14 5V V NC DD1 Q3 Q4 4 13 R8 R10 GND NC 1 15 15 D7 D8 5 12 12V V DISABLE DDB 6 11 V R4 V DD1 OB 7 ENCODE DECODE 10 470 R3 GND NC B 470 8 9 Q1, Q2, Q3, Q4: FDP5800 D1, D2: SSC54 D5, D6, D7, D8: 15ETH06FPPBF Z1, Z2: SMAZ5928B Figure 1. H-Bridge Using ADuM7234 Isolated Half-bridge Driver (Simplified Schematic: All Connections and Decoupling Not Shown) input of the of the ADuM7234, which has a 3.5 V threshold. ground. On the other hand, the source voltages of the high side Two jumpers are provided, which makes it easy to configure MOSFETs (Q1, Q2) switch as the pairs of MOSFETs are turned the polarity of the controlling PWM signal. on and off. Therefore the optimum gate drive signals should be referenced orbootstrappe to this floating voltage. H-Bridge Introduction The gate drive signals from the ADuM7234 offer the benefit of There are four switching elements in the H-bridge shown in true galvanic isolation between each input and each output. Figure 1 (Q1, Q2, Q3, Q4). The switches are turned on in pairs, Each output may be operated up to 350 V peak relative to the either high left side (Q1) and low right side (Q4) or low left side input, thereby supporting low-side switching to negative (Q3) and high right side (Q2). Keep in mind that the switches voltages. As a result, the ADuM7234 provides reliable control of on the same side of the bridge are never on at the same time. the switching characteristics of various MOSFET configurations The switches can be implemented using MOSFETs or IGBTs over a wide range of positive or negative switching voltages. For (insulated gate bipolar transistors) and use pulse width safety and ease of testing, a 12 V dc supply was chosen as the modulation (PWM) or other control signals from the controller power supply for this design. to turn the switches on and off, thereby changing the polarity of the load voltage. Bootstrapped Gate Drive Circuit The sources of the low side MOSFETs (Q3, Q4) are connected The power supplies to the gate drivers for the high-side to ground, therefore, their gate drive signal is also referenced to and low-side are different. The low-side gate drive voltage is Rev. 0 Page 2 of 6 5V ADuC7061MKZ GND PWM 2.5V PWM1 PWM0 09644-001