A3966: Dual Full-Bridge PWM Motor Driver

The A3966 is designed to drive both windings of a two-phase bipolar stepper motor. The device includes two full-bridges capable of continuous output currents of ±650 mA and operating voltages to 30 V. Motor winding current can be controlled by the internal fixed-frequency, pulse-width modulated (PWM), current-control circuitry. The peak load current limit is set by user selection of a reference voltage and current-sensing resistors.

The fixed-frequency pulse duration is set by a user-selected external RC timing network. The capacitor in the RC timing network also determines a user-selectable blanking window that prevents false triggering of the PWM current-control circuitry during switching transitions.

To reduce on-chip power dissipation, the full-bridge power outputs have been optimized for low saturation voltages. The sink drivers feature the Allegro patented Satlington® output structure. The Satlington outputs combine the low voltage drop of a saturated transistor and the high peak current capability of a Darlington.

For each bridge, a PHASE input controls load-current polarity by selecting the appropriate source and sink driver pair. For each bridge, an ENABLE input, when held high, disables the output drivers. Special power-up sequencing is not required. Internal circuit protection includes thermal shutdown with hysteresis, ground-clamp and flyback diodes, and crossover-current protection.

The A3966 is supplied in a 16-lead plastic wide SOIC with two pins internally fused to the die pad for enhanced thermal dissipation. These pins are at ground potential and need no electrical isolation. The device is lead (Pb) free, with 100% matte tin leadframe plating.

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  • ±650 mA continuous output current
  • 30 V output voltage rating
  • Internal fixed-frequency PWM current control
  • Satlington® sink drivers
  • User-selectable blanking window
  • Internal ground-clamp and flyback diodes
  • Internal thermal-shutdown circuitry
  • Crossover-current protection and UVLO protection

The A3966 is supplied in a 16-lead plastic wide SOIC with two pins internally fused to the die pad for enhanced thermal dissipation. These pins are at ground potential and need no electrical isolation. The device is lead (Pb) free, with 100% matte tin leadframe plating.

 LB-SOIC 24 pin

Frequently Asked Questions


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?

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?

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?

Package options include a 16-lead batwing SOIC. The 16-pin DIP is no longer available.


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".


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:


  1. RS - the external sense resistor. This should be non-inductive.
  2. RT - the external resistive component needed to set the internal oscillator's frequency.
  3. CT - the external capacitive component needed to set the internal oscillator's frequency.
  4. Decoupling capacitor - logic supply. A 0.01 µF ceramic capacitor is recommended.
  5. Decoupling capacitor - load supply. A 47 µF electrolytic capacitor is recommended.

Q9: What protection features come with the A3966?

  1. Thermal shutdown (TSD)
  2. Crossover current protection
  3. Under-voltage lockout (UVLO)
  4. Ground-clamp diodes
  5. 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."


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, see technical paper STP98-9, "Low-Cost-Dual-H-Bridge-Motor-Driver-IC".

There are no news items available for this product.

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Functional Block Diagram Typical Application Full-Step Chart Half-Step Chart Modified Half-Step Chart Modified Step Diagram Pinout Diagram Step Diagram

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Compliant
Part Composition /
RoHS Data
Comments Samples Check
Distributor Stock
A3966SLBTR-T 16-lead SOIC -20°C to 85°C Yes View Data Contact your
local sales rep
Check Stock

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.

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