Circuit Note CN-0415 Devices Connected/Referenced High Voltage, Bidirectional Current AD8210 Shunt Monitor 100 V Overvoltage, Undervoltage LTC4367 and Reverse Supply Protection Controller Circuits from the Lab reference circuits are engineered LTC4441 N-Channel MOSFET Gate Driver and tested for quick and easy system integration to help solve 14-Bit, 500 ksps Serial Sampling ADC todays analog, mixed-signal, and RF design challenges. LTC2312-14 in TSOT For more information and/or support, visit www.analog.com/CN0415. 60 ns, Low Power, Single-Supply, LT1671 Ground-Sensing Comparator High Voltage Step-Up/Step-Down LT3433 DC/DC Converter Low Voltage 1.15 V to 5.5 V, ADG3304 4-Channel, Bidirectional, Logic Level Translator Robust, Closed-Loop Control and Monitoring System for Solenoid Actuators For proportional valve applications, this circuit provides a com- EVALUATION AND DESIGN SUPPORT plete driver solution pulse-width modulation (PWM) duty Circuit Evaluation Boards cycle and frequency can be directly controlled by an external CN-0415 Circuit Evaluation Board (EVAL-CN0415-ARDZ) PID controller, and a dither current with programmable frequency Arduino form factor-compatible development board and amplitude can be enabled to reduce mechanical stiction. (EVAL-ADICUP3029) Design and Integration Files A high voltage, current shunt monitor measures the Schematics, Layout Files, Bill of Materials, Software instantaneous solenoid current, which is then digitized for software control. Full-scale current is 2.0 A, which can be CIRCUIT FUNCTION AND BENEFITS modified by changing a single shunt resistor. A redundant over- The simplified circuit diagram shown in Figure 1 is a robust current limit circuit continuously monitors solenoid current, solution for accurately and efficiently driving proportional and latching off and notifying the controller when tripped, two-state solenoid actuators. Applications include motion con- protecting the solenoid in the event of hardware or software trol, latches, clamps, brakes, clutches, proportional gas valves, faults. Power entry circuitry includes protection for overvoltage and proportional liquid valves. events up to 60 V and reverse voltage to 40 V, with power In two-state solenoid applications, this circuit provides accurate, being enabled within a valid window from 6 V to 24 V only, closed-loop current control, allowing low voltage solenoid use ensuring predictable operation over supply transient conditions, over a wide range of supply voltages. Initial pull-in current, pull-in for instance, undervoltage during cold cranking or overvoltage time delay, and hold current are independently adjustable, greatly resulting from a load dump. reducing power consumption in applications in which the solenoid is continuously energized. 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 2019 Analog Devices, Inc. All rights reserved. CN-0415 Circuit Note SWITCHING INPUT PROTECTION IC REGULATOR ADICUP3029 V = +5V LTC4367 LTC3433 CC (MCU) TVS+ + 6V TO 24V TVS MCU VIO SOLENOID 2A MAX ACTUATOR V CC MCU VIO V CURRENT CC SENSE AMPLIFIER R VDD VIO SENSE AD8210 0. 1 SPI LTC2312-14 V (OUT) REF V CC LT1671 2k PWM OVER-CURRENT 10k MONITORING V CC COMPARATOR V CC MCU VIO EN LTC4367 LTC4441 Figure 1. ELECTRICAL CIRCUIT DESCRIPTION CONNECTION + Fundamentals of Solenoid Actuator CASE OR FRAME The electrical characteristics of typical solenoid actuators are COIL WINDING primarily inductive and resistive. A voltage applied across a solenoid actuator causes a current to ramp with an initial slope PLUNGER of voltage/inductance (V/L), eventually reaching a steady state x current of voltage/resistance (V/R). This V/L/R characteristic is COIL WINDING STROKE the primary reason why current does not immediately reach a maximum level when a solenoid is energized. The solenoid RETURN SPRING MAGNETIC FLUX LINES stores energy in the form of a concentrated magnetic field. A Figure 2. Pull-type Linear Solenoid Construction magnetic field is generated around the conductor wire when- ever there is a current flow present in the wire. The magnetic The force on the armature of the solenoid is approximately field becomes concentrated with the wire wound into a coil, proportional to the current and inversely proportional to the such as in a solenoid. This electromagnet can control a mechanical square of the gap between the armature and core. Thus two- valve through an electrical signal. PWM can be used to reduce state solenoids typically have a return spring with a linear the effective voltage applied to a solenoid (and hence control response (or no return spring), whereas proportional solenoids the current of the solenoid), with the effective voltage being use a nonlinear spring such that armature displacement is expressed as follows: proportional to solenoid current. Armature movement does affect solenoid current (as shown in Figure 3), but this V Duty Cycle movement typically does not have a significant impact on In general, solenoid basically consist of an electrical coil wound circuit operation. around a cylindrical tube with a ferromagnetic actuator or plunger that is free to move or slide in and out of the body of the coil, as shown in Figure 2. Rev. 0 Page 2 of 8 MOUNTING BACKPLATE 17341-001 17341-002