ASW Datasheet PDF Download -, ASW data sheet. Data Sheet. † inductive loads, the ASB and ASW are capable of continuous The ASW, for higher package power dissipation. ASW Dmos Full-bridge PWM Motor Driver NC REF/BRAKE RC GROUND LOGIC SUPPLY PHASE Details, datasheet, quote on part number: ASW.

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These conditions can be tolerated but should be avoided.

Internal fixed off-time PWM current-control circuitry can be used to regulate the maximum load current to a desired value. The fixed off-time pulse duration is set by a userselected external RC timing network. Internal circuit protection includes thermal shutdown with hysteresis, transient suppression diodes, and crossover-current protection. Special power-up sequencing is not required. A user-selectable blanking window prevents false triggering of the PWM current control circuitry.

The brake function can be safely used to dynamically brake brush dc motors. The ASB is supplied in a pin dual in-line plastic package with copper heat-sink contact tabs.

The lead configuration enables easy attachment of a heat sink while fitting a standard printed wiring board layout. The ASW, for higher package power dissipation requirements, is supplied in a pin single in-line power-tab package.

Includes internal default Vsense level for over-current protection. Typical Data is for design information only. Each driver is tested separately. Negative current is defined as coming out of sourcing the specified device terminal. In forward or reverse mode the current-control circuitry limits the load current. When the load current reaches ITRIP, the comparator resets a latch to turn off the selected sink driver. The load inductance causes the current to recirculate through the source driver and flyback diode two-quadrant operation or slow decay.

At the end of the RTCT interval, the drivers are re-enabled allowing the load current to increase again. The PWM cycle repeats, maintaining the load current at the desired value see figure 2. However, if the back-EMF voltage is large and there is no PWM current limiting, then the load current can increase to a value that approaches a locked rotor condition. If so, the PWM cycle will repeat, limiting the load current to the desired value.

This is useful in applications with differing run and brake currents and no practical method of varying VREF. Because the kinetic energy stored in the motor and load inertia is being converted into current, which charges the VBB supply bulk capacitance power supply output and decoupling capacitancecare must be taken to ensure the capacitance is sufficient to absorb the energy without exceeding the voltage rating of any devices connected to the motor supply.


The one shot time, toff fixed off timeis determined by the selection of an external resistor RT and capacitor CT connected in parallel from the RC terminal to ground. Similarly, when a transition of the PHASE input occurs, CT is discharged to near ground during the crossover delay time the crossover delay time is present to prevent simultaneous conduction of the source and sink drivers.

After the crossover delay, CT is charged by an internal current source of approximately 1 mA. The comparator output remains blanked until the voltage on CT reaches approximately 3. When the device is re-enabled, CT is charged by the internal current source. This value ensures that the blanking time is sufficient to avoid false trips of the comparator under normal operating conditions. For optimal regulation of the load current, the above value for CT is recommended and the value of RT can be sized to determine toff.

For more information regarding load current regulation, see below. When the PWM latch is reset by the current comparator, the voltage on the RC terminal will begin to decay from approximately 3 volts. When the voltage on the RC terminal reaches approximately 1.

(PDF) A3951SW Datasheet download

In addition to determining the fixed off time of the PWM control circuit, the CT component sets the comparator blanking time. This directly relates to the limitations imposed by the VREF input 2. If the normal PWM current control is used, then the comparator blanking function is active during phase and 3a951sw transitions. When the device is enabled, the internal current-control circuitry will be active and can be used to limit the load current in the normal internal PWM slow-decay or two-quadrant mode of operation.

An internally generated dead time prevents crossover currents that can occur when switching phase or braking.

This is intended xatasheet to protect the device from failures due to excessive junction temperatures and should not imply that output short circuits are permitted. An internal under-voltage datashset circuit prevents simultaneous conduction of the outputs when the device is powered up or powered down.

This can have added benefits in bidirectional brush dc servo motor applications as the transfer function www. This should be taken into account when determining the impedance of the external circuit that sets the reference voltage value.

The use of sockets should be avoided as contact resistance can cause variations in the effective value of RS.


Larger values of RS reduce the aforementioned effects but can result in excessive heating and power loss in the sense resistor. In internal PWM applications, only the two datashedt flyback diodes need be added. Fixed Off-Time Selection With increasing values of toff, switching losses decrease, low-level load-current regulation improves, EMI is reduced, the PWM frequency will decrease, and ripple current will increase.

The value of toff can be chosen for optimization of these parameters. In this case, a dc voltage on the REF input is used typically to limit the maximum load current. This simplifies the servo-control loop because the transfer function between the duty cycle on the PHASE input and the average voltage applied to the motor is more linear than in the case of ENABLE PWM control which produces a discontinuous current at lowcurrent levels.


Similar to when braking the motor dynamically, abrupt changes in the direction of a rotating motor produce a current generated by the back EMF.

The current generated will depend on the mode of operation. When the direction of the motor is changed abruptly, the kinetic energy stored in the motor and load inertia will be converted into current that charges the VBB supply bulk capacitance power supply output and decoupling capacitance. Care must be taken to ensure the capacitance is sufficient to absorb the energy without exceeding the voltage rating of any devices connected to the motor supply.

EP The ASB and ASW may be used for bidrectional control of bipolar stepper motors with continuous output currents to 2 A and peak start-up currents as high as 3. MAA in Dimensions in Millimeters for reference only 16 0. Lead thickness is measured at seating plane or below. Lead spacing tolerance is non-cumulative. Leads indicated are internally one piece. MP in Dimensions in Millimeters for reference only Lead gauge plane is 0.

ASWInternet thinking Electronics Co., Electronic data resources trading network

Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc.

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