ALLEGRO A3977 PDF

ASLPTR-T. MOTOR DRIVER, STEPPER, 2 O/P, TSSOP ALLEGRO MICROSYSTEMS. Minimum Order: 1. £ Cut Tape. This board is based on Allegro Microsystems A Stepper Motor Driver IC. The A is a complete microstepping motor driver, with built-in translator. A Microstepping DMOS Driver with Translator FEATURES AND BENEFITS Allegro MicroSystems, LLC Northeast Cutoff Worcester, Massachusetts.

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Documents Flashcards Grammar checker. The A includes a fixed off-time current regulator that has the ability to operate in slow- fast- or mixed-decay modes. This current-decay control scheme results in reduced audible motor noise, alletro step accuracy, and reduced power dissipation.

The translator is the key to the easy implementation of the A Simply inputting one pulse on the STEP input drives the motor one step two logic inputs determine if it is a full- half- allegrro, or eighth-step.

There are no phase-sequence tables, high-frequency control lines, or complex interfaces to program. The A interface is an ideal allegeo for applications where a complex microprocessor is unavailable or over-burdened.

Internal synchronous-rectification control circuitry is provided to improve power dissipation during PWM operation.

Internal circuit protection includes thermal shutdown with hysteresis, undervoltage lockout UVLO and crossover-current protection. Special power-up sequencing is not required. Typical Data is for design information only.

Negative current is defined as coming out of sourcing the specified device terminal. It is designed to operate bipolar stepper motors in full- half- quarter- a39777 eighth-step modes.

The full-bridge current at each step is set by the value of an external current sense resistor RSa reference voltage VREFand the DACs output voltage controlled by the output of the translator. A low-to-high transition on the STEP input sequences the xllegro and advances the motor one increment.

The translator controls the input to the DACs and the direction of current flow in each winding. The size of the increment is determined by the state of inputs MS1 and MS2 see table 1.

A – Allegro Microsystems

At power up, or reset, the translator sets the DACs and phase current polarity to initial home state see figures for home-state conditionsand sets the current regulator for both phases to mixed-decay mode.

When a step command signal occurs on the STEP input the translator automatically sequences the DACs to the next level see table 2 for the current level sequence and current polarity. If the new DAC output level is lower than the previous level the decay mode for that full-bridge will be set by the PFD input fast, slow, or mixed decay. If the new DAC level is higher or equal to the previous level then the decay mode for that full-bridge will be slow decay.

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This automatic current-decay selection will improve microstepping performance by reducing the distortion of the current waveform due to the motor BEMF. At power up the translator is reset to the home state see figures for home state conditions. Changes to these inputs do not take effect until the STEP command see figure. Initially, a diagonal pair of source and sink DMOS outputs are enabled and current flows through the motor winding and RS.

When the voltage across the current-sense resistor equals the DAC output voltage, the current-sense comparator resets the PWM latch, which turns off the source driver slow-decay mode or the sink and source drivers fast- or mixed-decay modes. The maximum value of current limiting is set by the selection of RS and the voltage at the VREF input with a transconductance function approximated by: The one shot off-time, toff, is determined by the selection of an external resistor RT and capacitor CT connected from the RC timing terminal to ground.

In the aklegro of a fault excessive junction temperature, or low voltage on VCP the outputs of the device are disabled until the fault condition is removed. This function blanks the output of the current-sense comparator when the outputs are switched by the internal current-control circuitry.

A3977 Single Stepper Motor Driver Board

The VREG terminal should be decoupled with a 0. VREG is internally monitored and in the case of a fault condition, the outputs of the device are disabled. This disables much of the internal circuitry including the output DMOS, regulator, and charge pump. A logic high allows normal operation and startup of the device in the home position. When coming out of sleep mode, wait 1 ms before issuing a STEP command to allow the charge pump gate drive to allegeo.

If a,legro voltage at the PFD input is greater than 0.

A3977 – Allegro Microsystems

If the allefro on the PFD input is less than 0. Mixed decay is between these two levels. This terminal should be decoupled with a 0.

As the trip point is reached, the device will go into fast-decay mode until the voltage on the RC terminal decays to the voltage applied to the PFD terminal. The time that the device operates in fast decay is approximated by: This active-low input enables all of the DMOS outputs. When logic high the outputs are disabled.

This will reduce power dissipation significantly and eliminate the need for external Allegdo diodes for most applications.

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A Datasheet(PDF) – Allegro MicroSystems

When the SR input is logic low, active mode is allehro and synchronous rectification will occur. This mode prevents reversal of the load current by turning off synchronous rectification when a zero current level is detected. This prevents the motor winding from conducting in the reverse direction. The synchronous rectification can be set in either active mode or disabled mode.

Disabled Mode When the SR input is logic al,egro, synchronous rectification is disabled. This mode is typically used when external diodes are required to transfer power dissipation from the A package to the external diodes.

Maximum Wake-Up Time ns ns 1. Current Sensing The printed wiring board should use a heavy ground plane. To minimize inaccuracies caused by ground-trace IR drops in sensing the output current level, the current-sense resistor RS should have an independent ground return to the star ground of the device. This path should be as short as possible. The use of sockets should be avoided as they can introduce variation in RS w3977 to their contact resistance. For optimum electrical and thermal performance, the driver should be soldered directly onto the board.

Always drive the logic inputs with a low source impedance to increase noise immunity. Grounding A star ground system located close to the driver is recommended. The lead PLCC has the analog ground and the power ground internally bonded to the power tabs of the package leads 44, sllegro, 2, 11 — 13, 22 — 24, and 33 — It is intended only to protect the device from failures due to excessive junction temperatures and should not imply that output short circuits are permitted.

On the lead TSSOP package, the analog ground lead 7 and the power ground lead 21 must be connected together externally. The copper ground plane located under the exposed thermal pad is typically used as the star ground. Before placing an order, the user is cautioned to verify that the information being relied upon is current.

The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its alldgro. For the latest version of this document, visit our website: Sensitivity to foreign language speakers. Definition of Terms – Allegro Microsystems.