A3955SB Equivalent & Substitute Parts

Part Overview

The A3955SB is a bipolar motor driver IC manufactured by Allegro MicroSystems, designed for stepper motor control applications. This device integrates control and power stage functionality in a 16-DIP package, supporting step resolutions from full step to 1/8 microstepping. The A3955SB is classified as obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and production continuity.

Substiute Parts

A3955SB

Allegro MicroSystemsIn Stock: 1521A3955SB Datasheet

Current PartRFQ

TB6560AHQ,8

Toshiba Semiconductor and StorageIn Stock: 1000362TB6560AHQ,8 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the A3955SB is determined by the following critical parameters:

• Motor Type & Function: Bipolar stepper motor driver with fully integrated control and power stage
• Voltage Supply Range: 4.5V ~ 5.5V nominal supply voltage
• Interface Type: Parallel control interface
• Step Resolution Capability: Support for 1, 1/2, 1/4, and 1/8 step modes
• Output Configuration: Half-bridge topology for bipolar motor phase control
• Current Rating: Output current capability of 1.5A or greater
• Package Compatibility: Through-hole mounting suitable for legacy PCB designs

The TB6560AHQ,8 meets these substitution criteria while offering enhanced specifications in several areas, including higher output current, additional step resolution modes, and improved compliance status.

Parameter Comparison

Engineering Selection Recommendations

The TB6560AHQ,8 is the qualified substitute for the obsolete A3955SB based on the following engineering criteria:

Functional Compatibility: Both devices provide fully integrated bipolar stepper motor driver functionality with parallel control interfaces and support for 1, 1/2, 1/4, and 1/8 step resolutions. The TB6560AHQ,8 extends this capability to 1/16 microstepping.

Supply Voltage Alignment: Both operate within the 4.5V ~ 5.5V supply range, ensuring compatibility with existing power distribution architectures.

Product Status & Compliance: The A3955SB is obsolete and RoHS non-compliant. The TB6560AHQ,8 is actively manufactured and ROHS3 compliant, meeting current regulatory and supply chain requirements.

Performance Enhancement: The TB6560AHQ,8 provides superior output current capability (3A vs. 1.5A), enabling support for higher-torque stepper motors or dual-motor configurations.

Design Considerations: Substitution requires PCB redesign due to package footprint differences (16-DIP vs. 25-SSIP). Load voltage rating differs (A3955SB: 50V maximum; TB6560AHQ,8: 34V maximum); verify that motor supply voltage does not exceed 34V in the target application.

Frequently Asked Questions (FAQ)

Q: Can the TB6560AHQ,8 directly replace the A3955SB without PCB modification?

A: No. The A3955SB uses a 16-PowerDIP package while the TB6560AHQ,8 uses a 25-SSIP package with different pin assignments and physical dimensions. PCB redesign is required.

Q: What are the key electrical differences between these devices?

A: The TB6560AHQ,8 provides double the output current (3A vs. 1.5A), supports an additional 1/16 step resolution mode, and uses Power MOSFET output stages instead of bipolar transistors. The A3955SB supports higher load voltage (50V vs. 34V).

Q: Is the TB6560AHQ,8 suitable for applications requiring the full 50V load voltage of the A3955SB?

A: No. The TB6560AHQ,8 is rated for maximum 34V load voltage. If the application requires load voltages above 34V, alternative substitutes must be evaluated.

Q: Does the TB6560AHQ,8 maintain backward compatibility with existing firmware or control logic?

A: Both devices use parallel control interfaces and support the same step resolution modes (1, 1/2, 1/4, 1/8). However, the TB6560AHQ,8 has different pin assignments and additional features. Control firmware must be validated for the new device.

Q: What is the impact of the different output stage technologies (Bipolar vs. Power MOSFET)?

A: Power MOSFET output stages typically provide lower on-resistance and reduced power dissipation compared to bipolar transistor stages. This results in improved thermal performance and efficiency in the TB6560AHQ,8.

Q: Are there compliance or supply chain advantages to using the TB6560AHQ,8?

A: Yes. The TB6560AHQ,8 is actively manufactured, ROHS3 compliant, and has significantly higher inventory availability (1,000,300 pcs vs. 1,425 pcs for the A3955SB). The A3955SB is obsolete and non-compliant with current environmental regulations.