SLOSE98A December 2022 – September 2023 DRV8461
PRODUCTION DATA
The DRV8461 is an integrated motor-driver solution for bipolar stepper motors. The device integrates two N-channel power MOSFET H-bridges, current sense resistors, current regulation circuitry, and a microstepping indexer. The DRV8461 is capable of supporting wide supply voltage of 4.5 V to 65 V. The device is available in two packages - a 44-pin HTSSOP (DDW) package; and another 28-pin HTSSOP (PWP) package. The DRV8461 provides an output current up to 4.8-A peak, 3-A full-scale, or 2.1-A root mean square (rms). The actual full-scale and rms current depends on the ambient temperature, supply voltage, and PCB thermal design. To provide scalable voltage and current solutions for the system design, the DRV8461 DDW package is pin-to-pin compatible with the DRV8462 and DRV8452, and the PWP package is pin-to-pin compatible with DRV8424, DRV8426, DRV8452 and DRV8434.
The DRV8461 integrates the auto-torque feature to reduce power loss and improve system efficiency by adjusting output current according to the load torque. The SPI interface provides various options to optimize the performance of the auto-torque algorithm for specific motor and system use case. The stall detection feature detects and reports a motor stall condition to the system controller when the motor is obstructed or has reached an end-of-travel stop. Additionally, the standstill power saving mode reduces power loss when the motor is at holding position.
The DRV8461 uses an integrated current-sense architecture which eliminates the need for two external power sense resistors, hence saving significant board space, BOM cost, design efforts and reduces significant power consumption. This architecture eliminates the power dissipated in the sense resistors by using a current mirror approach and using the internal power MOSFETs for current sensing. Optional external power sense resistors can also be connected between the PGND pins and board ground to monitor motor health and for implementing closed-loop algorithms such as Field Oriented Control. The current regulation set point is adjusted by the voltage at the VREF pin. For the SPI interface, an 8-bit register allows the controller to scale the output current without needing to scale the VREF voltage reference; and another 8-bit register allows configuration of the holding current level for the purpose of reducing power loss at motor standstill.
A STEP/DIR pin interface allows an external controller to manage the direction and step rate of the stepper motor. The internal microstepping indexer can execute high-accuracy micro-stepping without requiring the external controller to manage the winding current level. The indexer is capable of full step, half step, and 1/4,1/8, 1/16, 1/32, 1/64, 1/128, and 1/256 microstepping. High microstepping contributes to significant audible noise reduction and smooth motion. The automatic microstepping mode interpolates the input step frequency to high resolution, thereby improving current regulation and reducing audible noise while running with a low frequency step input from the controller. The custom microstepping table allows adjusting the current waveform to the needs of a particular motor.
Stepper motor drivers need to re-circulate the winding current by implementing several types of decay modes, such as slow decay, mixed decay and fast decay. The DRV8461 supports smart tune decay modes. The smart tune is an innovative decay mechanism that automatically adjusts for optimal current regulation performance agnostic of supply voltage and motor speed variations and aging effects. Smart tune Ripple Control uses a variable off-time ripple current control scheme to minimize distortion of the motor winding current. Smart tune Dynamic Decay uses a fixed off-time dynamic fast decay percentage scheme. Along with the smart tune decay modes, the DRV8461 also features a silent step decay mode for noiseless operation at standstill and low speeds of rotation.
The device integrates a spread spectrum clocking feature for both the internal digital oscillator and internal charge pump. This feature minimizes the electromagnetic emissions from the device. A low-power sleep mode is included which allows the system to save power when not actively driving the motor.