A3959: DMOS Full-Bridge PWM Motor Driver

Designed for pulse-width modulated (PWM) current control of dc motors, the A3959SB, A3959SLB, and A3959SLP are capable of output currents to ±3 A and operating voltages to 50 V. Internal fixed off-time PWM current-control timing circuitry can be adjusted via control inputs to operate in slow, fast, and mixed current-decay modes.

PHASE and ENABLE input terminals are provided for use in controlling the speed and direction of a dc motor with externally applied PWM-control signals. Internal synchronous rectification control circuitry is provided to reduce power dissipation during PWM operation.

Internal circuit protection includes thermal shutdown with hysteresis, undervoltage monitoring of supply and charge pump, and crossover-current protection. Special power-up sequencing is not required.

The A3959SB/SLB/SLP is a choice of three power packages, a 24-pin plastic DIP with a copper batwing tab (package suffix 'B'), a 24-lead plastic SOIC with a copper batwing tab (package suffix 'LB'), and a thin (<1.2 mm) 28-lead plastic TSSOP with an exposed thermal pad (suffix 'LP'). In all cases, the power tab is at ground potential and needs no electrical isolation. Each package is available in a leadfree version (100% matte tin leadframe).

The A3959SB-T package variant is discontinued. Samples are no longer available. Date of status change: June 1, 2016.

Recommended Substitutions: For existing customer transition, and for new customers or new applications, refer to the A3959SLPTR-T and A3959SLBTR-T.

DATASHEETS
SAMPLE & BUY

Astrorep Inc. (Allegro and Sanken Semiconductors, Sanken Power Supplies)
141 John Street, Suite 300
Babylon, NY 11702
Phone: (631)422-2500
Fax: (631)422-2504
Web: www.astrorepinc.com
Email: donna.tweedy@astrorepinc.com

If this is not your local representative, find your local sales rep here.

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  • Features and BenefitsFeatures and Benefits
  • PackagingPackaging
  • Technical DocsTechnical Docs
  • NewsNews
  • ±3 A, 50 V Output Rating
  • Low rDS(on) Outputs (270 milliohms, Typical)
  • Mixed, Fast, and Slow Current-Decay Modes
  • Synchronous Rectification for Low Power Dissipation
  • Internal UVLO and Thermal-Shutdown Circuitry
  • Crossover-Current Protection
  • Internal Oscillator for Digital PWM Timing

The A3959SB/SLB/SLP is a choice of three power packages:

24-pin plastic DIP with a copper batwing tab (package suffix 'B'); Thin (<1.2 mm) 28-lead plastic TSSOP with an exposed thermal pad (suffix 'LP')

B and LP package combined

24-lead plastic SOIC with a copper batwing tab (package suffix 'LB')  

LB-Batwing SOIC 24 pin

In all cases, the power tab is at ground potential and needs no electrical isolation. Each package is available in a leadfree version (100% matte tin leadframe).

Design Support Tools

Frequently Asked Questions


Q1: Is there a reference design for the A3959?

Q2: What types of protection features does the A3959 offer?

Q3: What types of external components are required?

Q4: Do I need pull-up/pull-down resistors on the input pins?

Q5: What is the maximum allowable motor supply voltage?

Q6: The datasheet states an output current of ±3.0 A. Is this a peak current for the device, or a continuous current?

Q7: Is the A3959 a constant-current or a constant-voltage controlled device?

Q8: Are there any layout concerns I should be aware of?

Q9: What is the recommended minimum copper ground plane area for reducing power dissipation at high currents?

Q10: Are there special techniques to reduce the package power dissipation when running at high currents?

Q11: Is there an application note on the use of external diodes?

Q12: Do you have a recommended Schottky diode?

Q13: Can I run the maximum rated output current for each package option?

Q14: Is the A3959 capable of being used in portable applications?

Q15: Is there an application note for the A3959?

Q16: Is there a drop-in, or pin-for-pin, replacement for the A3959?



Q1: Is there a reference design for the A3959?

Yes, you can download a demonstration board schematic and bill of materials for the A3959, free of charge. Also, for a small fee, you can purchase the demonstration board.


Q2: What types of protection features does the A3959 offer?

The following protection features are provided:

  • Thermal shut down (TSD)
  • Undervoltage lockout (UVLO)
  • Crossover current protection
  • VREG and charge pump monitors

Q3: What types of external components are required?

The following components are required for correct operation of the A3959:

  1. RS, the external sense resistor, is required for the PWM current control circuit. This should be a noninductive type of resistor. Recommended maximum RS value can be calculated using RS = 0.5 / ITRIP(max). Using a reasonably smaller value for RS will dissipate less power in RS and provide headroom. There also needs to be a 0.1 µF mono/ceramic capacitor in parallel with the sense resistor.
  2. A 0.22 µF mono/ceramic capacitor must be placed between the CP1 and CP2 pins.
  3. The VREG pin should be decoupled with a 0.22 µF capacitor to ground.
  4. A LOGIC SUPPLY (VDD) decoupling capacitor is recommended: ceramic, rated at 0.1 µF.
  5. A LOAD SUPPLY (VBB) decoupling capacitor is recommended: electrolytic, rated at >47 µF. In addition, a 0.1 µF ceramic capacitor should be placed in parallel, if high frequency issues are a concern.
  6. If the SLEEP pin is not used, a 1 kΩ pull-up resistor to VDD is required.

Q4: Do I need pull-up/pull-down resistors on the input pins?

Not necessarily. The inputs can be tied directly to VDD or ground, depending on the logic level you desire. If pull-up/pull-down resistors are required for your particular design, 1 k to 4.7 kΩ resistors are recommended.


Q5: What is the maximum allowable motor supply voltage?

50 V. This must not be exceeded under any circumstances.


Q6: The datasheet states an output current of ±3.0 A. Is this a peak current for the device, or a continuous current?

The output current rating is for continuous current. The A3959 can handle a peak current of 6 A for <3 µs. Note: When running at high currents, power dissipation should be carefully considered. Caution should be taken to never exceed a junction temperature of 150°C when running the device.


Q7: Is the A3959 a constant-current or a constant-voltage controlled device?

The A3959 provides constant-current control. Motor winding current is controlled by an internal PWM current-control circuit, which incorporates an internal OSC circuit to set the fixed off-time, which is typically 24 µs.


Q8: Are there any layout concerns I should be aware of?

Yes. The sense resistor, RS, should be connected as close as possible to the device. The ground side of RS should return on a separate trace to the ground pin(s) of the device. RS should be noninductive, and the circuit board traces should be as large as physically possible. A 47 µF or larger electrolytic decoupling capacitor should be placed between the load supply pins and ground, and be placed as close as physically possible to the device.


Q9: What is the recommended minimum copper ground plane area for reducing power dissipation at high currents?

A ground plane area that is at least two times larger than the package outline is a good place to start. For further layout considerations, please refer to the following on the Allegro Web site: "Package Thermal Characteristics".


Q10: Are there special techniques to reduce the package power dissipation when running at high currents?

Use of external Schottky diodes with low VFORWARD, to clamp the outputs to VBB and ground, will help to reduce the power dissipation in the A3959. Heat sinks are also a possibility, but not as efficient. For additional information, please refer to the following, on the Allegro Web site: "Power Drive Circuits".


Q11: Is there an application note on the use of external diodes?

There is no application note about using external diodes on the A3959. Each of the outputs should have one Schottky diode connected to VBB (cathode to VBB) and one Schottky diode connected to ground (anode to ground, not to the sense pins). If the PFD1 and PDF2 input pins are set to "slow decay only," then use only two Schottky diodes between the outputs and ground. The two Schottky diodes from the outputs to VBB will not help improve thermal performance in slow decay mode.


Q12: Do you have a recommended Schottky diode?

We typically don't recommend a specific diode, due to the range of voltages and currents that can be used.


Q13: 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".


Q14: Is the A3959 capable of being used in portable applications?

Absolutely. The A3959 has Sleep mode, which minimizes power consumption when not in use. During Sleep mode, the device draws a maximum of 20 µA.


Q15: Is there an application note for the A3959?

Unfortunately, not at this time. However, the datasheet and these FAQs address the majority of the questions regarding the A3959.


Q16: Is there a drop-in, or pin-for-pin, replacement for the A3959?

No. The A3959 is generally a more cost-effective solution than most typical motor driver ICs due to its 3 A capability.

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Functional Block Diagram Pinout Diagram

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Compliant
Part Composition /
RoHS Data
Comments Samples Check
Distributor Stock
A3959SB-T 24-lead DIP -20°C to 85°C Yes View Data Discontinued Contact your
local sales rep
Check Stock
A3959SLBTR-T 24-lead SOIC -20°C to 85°C Yes View Data Contact your
local sales rep
Check Stock
A3959SLPTR-T 28-lead TSSOP -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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