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High-Performance Power ICs and Hall-Effect Sensors
Related Links:
Datasheets:
A3966: Dual Full-Bridge PWM Motor Driver (PDF)
Selection Guides:
Power Integrated Circuits,
Power Motor Drivers,
Power Motor Drivers - Full-Bridge
Technical Publications:
A New, Low-Cost, Dual H-Bridge Motor Driver IC (PDF),
A3966 Timing Diagram (full step),
A3966 Timing Diagram (half step),
A3966 Timing Diagram (modified half step)
FAQs:
3966: Dual Full-Bridge PWM Motor Driver FAQ
Press Releases:
Low Cost, Dual Full-Bridge PWM Motor Driver ICs
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FAQs - A3966 Dual Full-Bridge PWM Motor Driver 
Q1: Can I microstep with the A3966?
Q2: Is the A3966 a drop-in pin-for-pin replacement for the UDN2993?
Q3: Is the A3966 available in surface-mount and through-hole packages?
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 A3966?
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 A3966?
Q1: Can I microstep with the A3966?
No. However, you can run in full, half, and modified half-step modes.
Q2: Is the A3966 a drop-in pin-for-pin replacement for the UDN2993?
No, it is not a drop-in replacement, although the A3966 is an excellent functional replacement.
Q3: Is the A3966 available in surface-mount and through-hole packages?
Yes. Package options include a 16-lead batwing SOIC and a 16-pin DIP.
Q4: Is the A3966 really the lowest cost, smallest, best overall solution in the industry today for controlling bipolar stepper motors up to 650 mA?
Absolutely!
Q5: Are there applications tools available for this device?
Yes. We now have two different applications boards that will help simplify a new design using the A3966. Contact the Applications Group in Worcester for more information.
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 external Schottky diodes in parallel with the internal diodes, use of heat sinks, etc. Please refer to application note numbers 29501.4, "Improving Batwing Power Dissipation," and AN29501.5, "Computing IC Temperature Rise." These papers can be found in the "Technical Publications" section of Allgro's web site.
Q7: What is the maximum allowable motor supply voltage?
30V. This must not be exceeded.
Q8: Do I need any external components?
Yes. The following components are required:
- RS - the external sense resistor. This should be non-inductive.
- RT - the external resistive component needed to set the internal oscillator's frequency.
- CT - the external capacitive component needed to set the internal oscillator's frequency.
- Decoupling capacitor - logic supply. A 0.01 µF ceramic capacitor is recommended.
- Decoupling capacitor - load supply. A 47 µF electrolytic capacitor is recommended.
Q9: What protection features come with the A3966?
- Thermal shutdown (TSD)
- Crossover current protection
- Under-voltage lockout (UVLO)
- Ground-clamp diodes
- Flyback diodes
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. Also, 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 29501.5A, "Improving Batwing Power Dissipation." This paper can be found in the "Technical Publications" section of Allegro's web site. Click here to go directly to this publication.
Q11: Is this a constant-current or constant-voltage controlled device?
Constant-current. Motor winding current is controlled by internal fixed-frequency, PWM current-control circuitry. This device can also be run in "voltage mode" for DC motor applications.
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 diodes. Heat sinks are also a possibility. However, Schottky diodes are typically the preferred solution.
Q13: Has a technical paper been written for the A3966?
Yes. STP98.9 can be found on Allegro's "Technical Publications" page or can be viewed immediately by clicking here.