onsemi STK672-040-E Hybrid IC Stepper Motor Driver: Datasheet, Pinout, and Application Circuit Guide
The onsemi STK672-040-E is a unipolar, constant-current chopper type hybrid stepping motor driver integrated circuit. It is designed to simplify the design and implementation of high-performance stepper motor drive systems by integrating the control logic, power MOSFETs, and protection circuits into a single, compact package. This all-in-one solution is ideal for applications requiring precise motion control, such as in office automation equipment, factory automation systems, and medical instrumentation.
This guide provides an overview of its key specifications, pin configuration, and a fundamental application circuit.
Datasheet Overview and Key Specifications
The STK672-040-E datasheet provides all necessary information for designing a robust motor drive system. Key electrical and mechanical specifications include:
Motor Supply Voltage (VCC2): Up to +42V. This allows for driving a wide range of stepper motors and enables higher torque at higher speeds.
Output Current: 1.5 A (maximum). The output current per phase is user-adjustable via an external sense resistor.
Control Supply Voltage (VCC1): +5V. This logic-level voltage powers the internal control circuitry.
Excitation Modes: The IC supports all standard stepping modes: Full-step, Half-step, and Microstepping (up to 1/16 step), providing flexibility for smooth motion and precise positioning.
Built-in Protection Circuits: The device is protected against overcurrent (OCP) and thermal overload (TSD). The thermal shutdown feature automatically disables the output if the internal temperature becomes excessive, safeguarding the IC from damage.
Package: The module is built in a compact SIP (Single In-line Package) with an integrated heatsink, facilitating efficient thermal management and saving PCB space.
Pinout Configuration
Understanding the pinout is critical for proper connection. The STK672-040-E features a 15-pin SIP structure.
Key Pins and Their Functions:
Pin 1 (VCC1): +5V logic supply voltage input.
Pin 2 (CW/CCW): Clockwise/Counterclockwise rotation control input.
Pin 3 (CLK): Step pulse input. Each rising edge of the pulse advances the motor by one microstep.
Pin 4 (MO): Controls the excitation mode (Full/Half/Microstep) in combination with Pins 5 and 6.
Pin 5 (M1): Mode selection bit 1.
Pin 6 (RESET): Active-low reset input. When set low, the internal translator is reset.
Pin 7 (VREG): Connect a capacitor to GND for internal regulator stability.
Pin 8 (GND): Ground reference for the control logic.
Pin 9 (NC): No connection.
Pins 10, 11 (VCC2): High-voltage power supply input for the motor.
Pins 12, 13 (GND): Power ground for the motor drive stage.
Pin 14 (φA): Output for Motor Phase A.
Pin 15 (φĀ): Output for Motor Phase Ā (inverse of Phase A).
(Note: Pins for Phase B (φB, φB̄) are located on the opposite side of the package).
Pin (RNF): The external current-sense resistor is connected between this pin and ground to set the motor's peak current.
Typical Application Circuit Guide
A basic application circuit for the STK672-040-E involves connecting a microcontroller (MCU) to the driver's control inputs and the motor to its power outputs.
1. Power Supplies: Provide a clean, decoupled +5V to VCC1 (Pin 1) for the logic and a high-voltage supply (up to 42V) to VCC2 (Pins 10, 11) for the motor. Ensure large electrolytic capacitors are placed near these pins to handle current surges.
2. Microcontroller Interface: Connect the MCU's digital output pins to the control inputs: CLK (Pin 3), CW/CCW (Pin 2), and MO/M1 (Pins 4, 5). Use pull-up or pull-down resistors as necessary to define default states.
3. Current Setting: The most critical external component is the current-sense resistor (RNF). Its value is calculated using the formula derived from the datasheet: `RNF = Vref / Ipk`, where `Vref` is a fixed internal reference voltage (typically ~0.5V) and `Ipk` is the desired peak motor current. A low-inductance, high-power-rated resistor must be used.
4. Motor Connection: Connect the four leads of your unipolar 6-wire stepper motor to the four output pins: φA, φĀ, φB, and φB̄. The two common wires of the motor are connected together to the positive motor supply (VCC2).
5. Decoupling and Stability: Place a 0.1µF ceramic capacitor close to the VCC1 pin to ground for noise suppression. A larger capacitor (e.g., 1µF) is also recommended on the VREG pin (Pin 7) to ground for stability of the internal regulator.
6. Heatsinking: Although the package has an integrated heatsink, for higher current applications, additional heatsinking might be required to ensure the module operates within its safe temperature range.
ICGOODFIND: The onsemi STK672-040-E is a highly integrated and robust solution for driving unipolar stepper motors. Its built-in translator for microstepping and comprehensive protection features significantly reduce design complexity and part count, making it an excellent choice for engineers seeking to develop reliable and high-performance motion control systems without designing a driver from scratch.
Keywords: Stepper Motor Driver, Microstepping, Unipolar, Constant-Current Chopper, Thermal Shutdown.
