Part Number: A3977SLPTR-T

Manufacturer: Allegro MicroSystems

Description: IC MTR DRV BIPOLR 3-5.5V 28TSSOP

Shipped from: Shenzhen/HK Warehouse

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Technical Specifications of A3977SLPTR-T

Datasheet  A3977SLPTR-T datasheet
Category Integrated Circuits (ICs)
Family PMIC – Motor Drivers, Controllers
Manufacturer Allegro MicroSystems, LLC
Packaging Tape & Reel (TR)
Part Status Active
Motor Type – Stepper Bipolar
Motor Type – AC, DC
Function Driver – Fully Integrated, Control and Power Stage
Output Configuration Half Bridge (4)
Interface Step/Direction
Technology DMOS
Step Resolution 1, 1/2, 1/4, 1/8
Applications General Purpose
Current – Output 2.5A
Voltage – Supply 3 V ~ 5.5 V
Voltage – Load 8 V ~ 35 V
Operating Temperature -20°C ~ 150°C (TJ)
Mounting Type Surface Mount
Package / Case 28-TSSOP (0.173″, 4.40mm Width) Exposed Pad
Supplier Device Package 28-TSSOP-EP

A3977SLPTR-T Description

The A3977 is a complete micro-stepping motor driver and integrated translator. It is intended to fully run bipolar stepper motors, half, quarter, and eighth-step modes and has an output drive capability of 35 V and 2.5 A. The A3977 includes a fixed off-time current regulator operating in rapid, slow, or mixed decay modes. This decay control strategy improves step accuracy, lowers motor noise, and uses less power. The straightforward implementation of the A3977 depends on the translator.

The motor can be moved one step by simply applying one pulse to the STEP input (two logic inputs control whether it is a full, half, quarter, or eighth step). There aren’t any complicated interfaces, high-frequency control lines, or phase-sequence tables that need programming. Applications where a complicated microprocessor is not accessible or is too busy should use the A3977 interface. Power dissipation during PWM operation is enhanced by internal synchronous-rectification control circuitry. Undervoltage lockout (UVLO), crossover-current protection, and thermal shutdown with hysteresis are all types of internal circuit protection. It’s not necessary to sequence special power-ups.

A tiny 28-pin TSSOP package with an exposed thermal pad houses the motor driver integrated circuit A3977. This package variation is perfect for applications with a shortage of space because its height is less than 1.2 mm. Additionally, lead (Pb) free, the A3977 has a 100% matte tin lead frame coating. By doing this, the device complies with the RoHS directive and is guaranteed to be ecologically benign. The exposed thermal pad aids in the IC’s heat dissipation, enhancing the IC’s overall thermal performance.

The A3977 is useful for various applications, including printers, scanners, and other office machinery. It is made to drive bipolar stepper motors in full-, half-, and microstepping modes. The A3977 is a dependable and adaptable option for designers searching for a trustworthy motor driver solution because of its tiny form size, lead-free composition, and sophisticated motor control functions.

Features and Benefits

  • 5 A, 35 V maximum output.
  • Low RDS(on) outputs, typically 0.28 source, 0.22 sink.
  • Automatic detection and selection of the current decay mode.
  • Range of logic supply voltages: 3.0 to 5.5 V.
  • modes of mixed, quick, and gradual current decay.
  • production at home.
  • Low power dissipation with synchronous rectification.
  • Circuitry for the internal thermal and UVLO shutdown.
  • crossing-current defense.

Device Operation

The A3977 is an integrated translator and comprehensive microstepping motor driver that allows simple operation with few control lines. Bipolar stepper motors can be used with it in full-, half-, quarter-, and eighth-step modes. The two output full-bridges, both N-channel DMOS devices, have control circuitry that uses pulse-width modulation (PWM) with a fixed off-time. An external current sense resistor (RS), a reference voltage (VREF), and the DAC’s output voltage, regulated by the translator’s output, all impact the full-bridge current at each step.

The translator initializes the DACs and phase current polarity to the original home state (see figures for the home state conditions) and switches the current regulators for both phases to mixed-decay mode upon power-up or reset. The translator automatically advances the DACs to the next level when a step command signal is received on the STEP input (the current level sequence and current polarity are shown in Table 2). Inputs MS1 and MS2 determine the micro-step resolution.

The full-bridge’s decay style (rapid, slow, or mixed decay) will be determined by the PFD input if the new DAC output level is lower than the previous level. The full-bridge’s decay mode will be slow if the new DAC level is greater than or equal to the previous level. By minimizing current waveform distortion brought on by the motor BEMF, this automatic current-decay selection will enhance microstepping performance.

● Reset Input (RESET)

The RESET input (active low) restarts the translator and disables all DMOS outputs, returning it to a predetermined home state (see figures for home state conditions). Until the RESET input turns high, the HOME output is low, and no STEP inputs are considered.

● Home Output (HOME)

The HOME output is a logic output that represents the translator’s starting condition. When turned on, the translator is reset to its default settings.

● Step Input (STEP)

A low-to-high transition on the STEP input puts the translator in sequence and moves the motor forward by one step. The translator regulates the input to the DACs and the current flow through each winding. The status of inputs MS1 and MS2 determines the increment’s magnitude.

● Shutdown

The device’s outputs are shut off during a fault (high junction temperature, low voltage on VCP, etc.) until the fault state is corrected. The undervoltage lockout (UVLO) circuit turns off the drivers and switches the translator back to the HOME state during power-up and in the case of low VDD.

● Sleep Mode (SLEEP)

When not in use, this active-low control input helps reduce power usage. The output DMOS, regulator, and charge pump are among the internal circuitry components that are disabled as a result. A high logic enables the device to start up normally and operate in the home position. Wait 1 ms after exiting sleep mode before sending a STEP command to give the charge pump (gate drive) time to stabilize.

● Percent Fast Decay Input (PFD)

Depending on the voltage level at the PFD input, a STEP input signal that commands a lower output current from the preceding step might command a gradual, fast, or mixed decay of the output current. Choosing the slow-decay mode depends on whether the voltage at the PFD input is larger than 0.6 VDD. Fast-decay mode is chosen if the PFD input voltage is less than 0.21 VDD. These two layers are separated by mixed deterioration. With a 0.1 F capacitor, this terminal needs to be decoupled.

● Synchronous Rectification

When a PWM off-cycle is initiated by an internal fixed off-time cycle, load current recycles in accordance with the decay mode selected by the control logic. In order to effectively short out the body diodes with the low RDS(on) driver, the synchronous rectification function of the A3977 will turn on the relevant MOSFETs during the current decline. Due to the large reduction in power dissipation, most applications won’t require external Schottky diodes. You can choose between active mode and disabled mode for synchronous rectification.

● Active Mode

Synchronous rectification occurs when the SR input is logic low, activating active mode. Disabling synchronous rectification when a zero current level is detected this option prevents the load current from being reversed. As a result, the motor winding cannot conduct in the other direction.


In conclusion, the A3977 is an innovative motor control integrated circuit that is both flexible and environmentally friendly. It is the perfect option for applications that require a small footprint due to its thin 28-pin TSSOP packaging with an exposed thermal pad. The 100% matte tin lead frame plating makes the device RoHS-compliant and environmentally safe. The A3977 is useful for various applications, including printers, scanners, and other office equipment, because it is made to drive bipolar stepper motors in full-, half-, and micro-stepping modes.

The IC’s total thermal performance is enhanced by the exposed thermal pad’s ability to dissipate heat produced by the IC. Overall, the A3977 is a trustworthy and effective motor driver solution for designers wishing to enhance their motor control designs. You can trust ICRFQ to help you find the A3977 or any other electronic part you need cheaply. They provide a variety of affordable options for purchasing electronic components. To learn more about their services, get in touch with them.

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