IN Brief:
- STL8300 integrates an 8051 MCU, three-phase BLDC controller, gate driver, charge pump, LDOs, and protection functions.
- The controller operates from 10V to 28V and supports sine-wave PWM, open- and closed-loop control, and ±0.5% speed accuracy.
- Weltrend is targeting compact paper-feed, scanning, and other office-automation motor systems.
Weltrend Semiconductor has launched the STL8300, a highly integrated three-phase BLDC motor controller designed for compact office-automation mechanisms including paper-feed and scanning systems.
Developed by Weltrend subsidiary Sentelic, the device combines an 8-bit 8051 processor core with motor-control, analogue, gate-drive and protection functions that would otherwise require several external components. Its 10V to 28V operating range is intended for 24V-class motor systems, with external power devices driven from the integrated three-phase gate-driver architecture.
The device supports sinusoidal PWM commutation using three Hall sensors, together with both open- and closed-loop control. Weltrend specifies speed accuracy of ±0.5% and a maximum settling time of 0.4 seconds, parameters that matter in mechanisms where motor behaviour has to remain synchronised with paper position, scanning or other electromechanical operations.
The processor is a single-cycle 1T implementation of the 8051 architecture running at up to 24MHz from an internal RC oscillator. That is modest general-purpose compute performance by current MCU standards, but BLDC control does not depend on CPU throughput alone. Dedicated PWM, timing, sensing and protection hardware can remove repetitive motor functions from the processor and make response more deterministic.
Six PWM channels provide up to 11-bit resolution at a 48MHz PWM clock for three-phase full-wave motor control. The controller also includes a 10-bit ADC with conversion rates up to 500ksps, Hall-sensor amplification and an FG pattern amplifier and comparator.
Those analogue blocks reduce the amount of external signal conditioning required between the motor sensors and the digital control logic. Motor-controller PCB layouts often have to accommodate relatively sensitive position and current measurements close to switching nodes carrying much larger voltage and current transitions, making integration useful for both board area and routing complexity.
The STL8300 also integrates a charge pump and low-dropout regulators, together with current-limit, over-voltage, under-voltage and lock protection. Speed commands can be supplied through clock, PWM or analogue inputs, giving equipment designers several options for connecting the motor stage to the wider machine controller.
Office automation is a demanding application despite relatively modest motor power. Feed rollers, scanner mechanisms and similar assemblies operate close to users, so audible noise, vibration and smooth low-speed movement can be more visible than in larger industrial machinery.
Sinusoidal drive helps address some of those mechanical effects by reducing torque ripple compared with simpler commutation schemes. The quality of the finished mechanism will still depend on the motor, bearings, gearing and mechanical structure, but smoother electrical commutation gives designers another variable to control before resorting to mechanical changes.
Standby consumption is also significant in printers, scanners and other office equipment that can spend much of their operating life idle. Weltrend specifies standby current below 100µA, typically around 80µA, allowing the motor-control electronics to remain available without dominating the machine’s low-power state.
Integration becomes especially useful as the motor electronics move closer to the mechanism. A design using a separate MCU, gate driver, analogue front end, regulators and protection ICs creates additional board area and routing between blocks that have to operate in a relatively noisy switching environment.
Combining those functions does not remove the need to design external power devices, current paths and thermal behaviour around the motor load, but it reduces the number of interfaces between the control blocks.
The STL8300 is supplied in a 40-lead QFN measuring 6 × 6mm. Its package size and integrated peripheral set position it for assemblies where the motor controller has to fit close to the drive mechanism rather than on a large central electronics board.
The device therefore follows a familiar direction in motor electronics: less emphasis on adding general-purpose processor performance and more on consolidating the functions directly involved in sensing, commutation, protection and power-stage control. For compact 24V BLDC systems, that integration can matter more than the headline clock speed of the embedded processor.
