1 System Description

Many home appliances like HVAC zone dampers, electronic expansion devices, and water valves use multiple stepper motors, brushed DC motors, and many solenoid valves and actuators for operation. This reference design demonstrates a dual-motor drive design using a BLDC motor control IC and a stepper motor control IC. Both devices support a wide operating voltage range, and have features such as smart tune ripple and dynamic decay control and protection features including supply undervoltage lockout, overvoltage protection, charge pump undervoltage, overcurrent protection, over temperature warning and over-temperature shutdown

This design also considers industry recognized communication methods/protocols used to communicate with the motor control devices for dampers and electronic valves. A TCAN334 can transceiver is included in the design, paired with the dedicated CAN features of the MSPM0G3507 and the M0 SDK for quicker implementation. Both 0-10V control and 4-20mA control interfaces are also integrated for real-time control of the damper or expansion valve position from a host controller. The reliability and robustness of the system is further increased by surge protection provided by the TVS1401 at the control interface. In the case where only fully open or fully closed control is needed, this reference design incorporates an ISO1212 for field side fully open/fully closed control of the damper/valve.

Many household appliances have to be designed to meet specific UL (Underwriters Laboratories) or IEC (International Electrotechnical Commission) safety standards. For example, IEC 60335-1 and IEC 60730 are typically followed for household appliances. The standards define low-power circuit (LPC) in home appliances subsystems. A low-power point can be identified as the node where the maximum power delivered is less than 15W. The part of the circuit farther from the supply source than a low-power point is considered as a low-power circuit. A proven LPC can help to skip the glow wire test, needle flame test, and certain abnormal fault conditions as per the definition and requirements from the respective standards, leading to reduced qualification and design time, and money.

The use of an eFuse at the input of those sub-systems helps to achieve a precise power limit even during abnormal fault conditions. The design with the TPS16410 e-Fuse at the 24V-42V input can help the designer to qualify the circuit as a low-power circuit. The reference design shows <3% error in input power limit during testing which helps with qualification as a low-power circuit, defined by IEC 60335-1.