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.
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')
24-lead plastic SOIC with a copper batwing tab (package suffix 'LB')
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 following protection features are provided:
The following components are required for correct operation of the A3959:
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.
50 V. This must not be exceeded under any circumstances.
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.
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.
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.
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".
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".
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.
We typically don't recommend a specific diode, due to the range of voltages and currents that can be used.
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".
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.
Unfortunately, not at this time. However, the datasheet and these FAQs address the majority of the questions regarding the A3959.
No. The A3959 is generally a more cost-effective solution than most typical motor driver ICs due to its 3 A capability.
There are no news items available for this product.
|Part Number||Package Type||Temperature||RoHS
|Part Composition /
|A3959SB-T||24-lead DIP||-20°C to 85°C||Yes||View Data||Discontinued||Contact your
local sales rep
|A3959SLBTR-T||24-lead SOIC||-20°C to 85°C||Yes||View Data||Contact your
local sales rep
|A3959SLPTR-T||28-lead TSSOP||-20°C to 85°C||Yes||View Data||Contact your
local sales rep