Allegro MicroSystems, Inc. Site Map • Contact Us
中文 • English

High-Performance Power ICs and Hall-Effect Sensors

Related Links:

Datasheets:
A3958: Full-Bridge PWM Motor Driver (PDF)

Selection Guides:
Power Integrated Circuits,

Power Motor Drivers,

Power Motor Drivers - Full-Bridge

when this product is updated

Technical Publications:
A New Serial-Controlled Motor Driver IC (PDF)

FAQs:
3958: Full-Bridge PWM Motor Driver FAQ

Product Evaluation Kits:
A3958SB Product Evaluation Kit

FAQs - A3958 Full-Bridge PWM Motor Driver ....

Q1: Can I microstep with the A3958?

Q2: Is the A3958 a replacement for any other device?

Q3: Is the A3958 available in surface-mount and through-hole packages?

Q4: Is the A3958 really the lowest cost, smallest, best overall solution in the industry today for controlling bipolar DC motors up to +/-2 A?

Q5: Are there applications tools available for this device?

Q6: Can I run the maximum rated output current for each package option?

Q7: What is the maximum allowable motor supply voltage?

Q8: Do I need any external components?

Q9: What protection features come with the A3958?

Q10: Are there layout concerns that I should be aware of?

Q11: Is this a constant-current or constant-voltage controlled device?

Q12: How can I increase the current in the winding and not exceed the power rating of the package?

Q13: Has a technical paper been written for the A3958?

Q1: Can I microstep with the A3958?

Yes, it is possible, but if microstepping is preferred, the 3972 is recommended.

Q2: Is the A3958 a drop-in pin-for-pin replacement for any other device?

No.

Q3: Is the A3958 available in surface-mount and through-hole packages?

Yes. Package options include a 24-lead batwing SOIC and a 24-pin DIP.

Q4: Is the A3958 really the lowest cost, smallest, best overall solution in the industry today for controlling bipolar DC motors up to +/-2 A?

Absolutely! Without question.

Q5: Is there an application tool available for this device?

Yes. We now have a product evaluation kit that will help simplify a new design using the A3958, available through our On-Line Store.

Q6: Can I run the maximum rated output current for each package option?

It is possible. However, there are several considerations, such as optimization of circuit board layout, use of heat sinks, etc. Please refer to application note numbers: AN29501.4, "Computing IC Temperature Rise", and 29501.5, "Improving Batwing Power Dissipation".

Q7: What is the maximum allowable motor supply voltage?

50 V. This must not be exceeded.

Q8: Do I need any external components?

Yes. The following components are required:

  1. RS - the external sense resistor. This should be non-inductive.
  2. Charge pump capacitor across pins CP1 and CP2. A 0.22 µF capacitor is recommended.
  3. Motor voltage pin 1. A 0.22 µF ceramic capacitor is recommended.
  4. Decoupling capacitor - logic supply. A 0.22 µF ceramic capacitor is recommended.
  5. Decoupling capacitor - load supply. A 47 µF electrolytic capacitor is recommended.
  6. A 0.1 µF capacitor across RS
  7. Decoupling capacitor - Reference Voltage pin. A 0.22 µF ceramic capacitor is recommended.

Q9: What protection features come with the A3958?

  1. Thermal shutdown (TSD)
  2. Crossover current protection
  3. Under-voltage lockout (UVLO)
  4. Charge pump monitor

Q10: Are there layout concerns that I should be aware of?

Yes. Power ground for the sense resistor, RS, should be connected as close to the device as possible, and should be returned separately to the ground pins of the device. RS should be non-inductive, and the circuit board ground run should be as large as physically possible. For further layout consideration, please refer to application note 29501.5, "Improving Batwing Power Dissipation".

Q11: Is this a current-controlled or voltage-controlled device?

Both current and voltage controlled. The A3958 incorporates a fixed-off time PWM circuit to regulate the current in the winding of the DC motor.

Q12: How can I increase the current in the winding and not exceed the power rating of the package?

Use external Schottky diodes in parallel with the internal DMOS body diodes. Heat sinks are also a possibility. However, Schottky diodes are typically the preferred solution.

Q13: Has a technical paper been written for the A3958?

Yes. STP99-12, "A New Serial-Controlled Motor Driver IC".

Copyright © 2008 Allegro MicroSystems, Inc. • 115 Northeast Cutoff, Worcester, MA 01606 USA • Phone: 1.508.853.5000 • Fax: 1.508.853.7895