This part is discontinued. Samples are no longer available. Date of status change: June 1, 2016.
Recommended substitution: A3992SLPTR-T.
Designed for pulse-width modulated (PWM) current control of bipolar microstepping stepper motors, the A3972SB is capable of continuous output currents to ±1.5 A and operating voltages to 50 V. Internal fixed off-time PWM current-control timing circuitry can be programmed via a serial interface to operate in slow, fast, and mixed current-decay modes.
The desired load-current level is set via the serial port with two 6-bit linear DACs in conjunction with a reference voltage. The six bits of control allow maximum flexibility in torque control for a variety of step methods, from microstepping to full step drive. Load current is set in 1.56% increments of the maximum value.
Synchronous rectification circuitry allows the load current to flow through the low rDS(on) of the DMOS output driver during the current decay. This feature will eliminate the need for external clamp diodes in most applications, saving cost and external component count, while minimizing power dissipation.
Internal circuit protection includes thermal shutdown with hysteresis, transient-suppression diodes, and crossover-current protection. Special power-up sequencing is not required.
Full, half, quarter, one-eighth, one-sixteenth, and one-thirty-second step modes are possible. In addition, the onboard linear DAC allows current to be programmed in 1.56% increments of the maximum value 100%/64.
It is used by Allegro for testing during production. It should NOT be used in actual applications.
This device is currently available only in a 24-lead plastic "batwing" DIP package. However, the A3992, the next generation version of the A3972, will be released in January 2006. That will be available in a 24-pin TSSOP package with exposed thermal pad.
Sleep mode disables all circuits, including UVLO, and resets the serial port to all zeros. Idle mode disables all circuits except UVLO.
The APEK3972 demo board is no longer available.
50 V. This must not be exceeded.
Yes. The following components are required:
Yes. Power ground for the sense resistor, Rs, should be connected as close to the device as possible. The ground side of the sense resistor should return on a separate trace to the ground pin(s) of thes device. Also, Rs should be non-inductive, and the circuit board ground run should be as large as physically possible. Finally, a 47 µF electrolytic decoupling capacitor should be placed between the load supply pins and ground. For further layout considerations, please refer to application note 29501.5A, "Improving Batwing Power Dissipation".
Constant-current. Motor winding current is controlled by internal fixed-offtime, PWM current-control circuitry.
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 A3972. Heat sinks are also a possibility, but not as efficient. Note: When using external diodes, synchronous rectification should be disabled to achieve maximum results. For additional information, please refer to the application note AN29504.8, "Power Drive Circuits".
There is no application note about using external diodes for the A3972. In most applications, each of the outputs should have one Schottky diode connected to VBB (cathode to VBB), and also one Schottky diode connected to ground (anode to ground, not to the sense pins).
We typically don't recommend a specific diode due to the range of voltages and currents that can be used. The V/I rating of the diode should be greater than or equal to the application requirements.
A ground plane area at least two times larger than the package outline is a good place to start. For further layout considerations, please refer to application note 29501.5A, "Improving Batwing Power Dissipation".
Not at this time, but one is planned for the future.
Like typical shift registers, the most recent bits are the ones that are retained. As an example, if 24 bits are clocked in , the last 19 are the ones that will be used.
No. Since Word 0 and Word 1 are separate, they cannot write to each other or over each other. The appropriate word has to be selected to be overwritten.
Pull it up to VDD through a 51 kW resistor or ground it. It should be noted that accuracy will be improved if the 51 kW resistor to VDD is used.
Let it float.
Yes. The A3972 has Sleep mode, which minimizes power consumption when the device is not in use. During Sleep mode, the device only draws a maximum of 100 µA. The logic supply voltage range of 3.3 to 5.5 V makes it compatible with some battery operated equipment.
Each application is different. For this reason, there isn’t a recommended setup. However, when evaluating the A3972, care should be taken to ensure that the motor will start up and run. This can be achieved by choosing (addressing) the Word 0 and Word 1 bit assigments for a mid-range setting. Specifically, set the following bits initially:
|Word 0||Word 1|
|D1 through D6
D7 through D12
|D1 and D2|
D3 through D7
D8 through D12
This configuration allows the motor to start and run. After it is running, adjust the bit assignments slightly for optimum performance.
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|Part Number||Package Type||Temperature||RoHS
|Part Composition /
|A3972SB-T||24-lead DIP||-20°C to 85°C||Yes||View Data||Discontinued||Contact your
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