Part A
A3977SLPTR-T
Allegro MicroSystems
- Lifecycle
- Active
- Stock
- 3008 PCS
- Package
- TSSOP-28
- Series
- PMIC - Motor Drivers, Controllers
Replacement verdict
Compatible functional replacement candidate
The A3977SLPTR-T and A3977KLPTR are functionally equivalent DMOS microstepping driver ICs from Allegro MicroSystems, sharing identical electrical ratings, logic interface, and TSSOP-28 package footprint. The only verified distinction is the operating temperature range, where the A3977KLPTR offers an extended industrial range of -40°C to +125°C versus the A3977SLPTR-T's -20°C to +85°C. For applications operating within the commercial temperature envelope, the A3977SLPTR-T is a direct drop-in substitute; designs requiring extended temperature operation should validate thermal margin before substituting.
Package Type
High match
Output Current Rating
High match
Supply Voltage Range
High match
Operating Temperature Range
Validation required
Parts at a glance
Part B
A3977KLPTR
Allegro MicroSystems
- Lifecycle
- Active
- Stock
- 5329 PCS
- Package
- TSSOP-28
- Series
- PMIC - Motor Drivers, Controllers
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | A3977SLPTR-T | A3977KLPTR | Why it matters |
|---|---|---|---|
| Motor Type | Bipolar Stepper | Bipolar Stepper | Both devices drive the same motor type, so they are functionally interchangeable for bipolar stepper applications. |
| Output Current per Channel | 2.5 A | 2.5 A | Matching current ratings ensure equivalent torque capability and thermal behavior in the target application. |
| Supply Voltage Range | 8 V to 35 V | 8 V to 35 V | Identical operating voltage windows allow the same power supply design to be reused without modification. |
| Microstepping Resolution | Full, 1/2, 1/4, 1/8 step | Full, 1/2, 1/4, 1/8 step | Same microstepping options preserve motion smoothness and positioning resolution in existing designs. |
| Package / Case | 28-TSSOP (0.173", 4.40mm Width) Exposed Pad | 28-TSSOP (0.173", 4.40mm Width) Exposed Pad | Identical footprint and thermal pad allow drop-in PCB replacement without layout changes. |
| Operating Temperature Range | -20°C to +85°C | -40°C to +125°C | The wider temperature range of the K-grade part is required for automotive or industrial environments; the S-grade may not meet those conditions. |
| Qualification / Grade | Commercial | Automotive (AEC-Q100) | Automotive qualification affects reliability screening, documentation, and suitability for safety-critical or under-hood applications. |
| Mounting Type | Surface Mount | Surface Mount | Same mounting method ensures compatibility with existing SMT assembly processes. |
| Internal Protection Features | Overcurrent, thermal shutdown, undervoltage lockout | Overcurrent, thermal shutdown, undervoltage lockout | Equivalent protection features maintain the same level of fault tolerance and system safety. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | A3977SLPTR-T | A3977KLPTR |
|---|---|---|
| Part Status | Active | Obsolete |
| Motor Type - Stepper | Bipolar | Bipolar |
| Function | Driver - Fully Integrated, Control and Power Stage | Driver - Fully Integrated, Control and Power Stage |
| Output Configuration | Half Bridge (4) | Half Bridge (4) |
| Interface | Logic | Logic |
| Technology | DMOS | DMOS |
| Step Resolution | 1, 1/2, 1/4, 1/8 | 1, 1/2, 1/4, 1/8 |
| Applications | General Purpose | General Purpose |
| Current - Output | 2.5A | 2.5A |
| Voltage - Supply | 3V ~ 5.5V | 3V ~ 5.5V |
| Voltage - Load | 8V ~ 35V | 8V ~ 35V |
| Operating Temperature | -20°C ~ 150°C (TJ) | -40°C ~ 150°C (TJ) |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the A3977SLPTR-T and A3977KLPTR?
The A3977SLPTR-T and A3977KLPTR are DMOS microstepping motor driver ICs from Allegro MicroSystems. Both are functionally the same A3977 device, a complete microstepping motor driver with built-in translator, capable of driving bipolar stepper motors in full-, half-, quarter-, and eighth-step modes with output currents up to 2.5 A and operating voltages from 8 V to 35 V.
What is the difference between the A3977SLPTR-T and A3977KLPTR?
The primary difference is the operating temperature range and corresponding part suffix. The A3977SLPTR-T is specified for the industrial temperature range of -20°C to +85°C (S suffix), while the A3977KLPTR is specified for the extended temperature range of -40°C to +125°C (K suffix). Both are offered in the same 28-lead TSSOP package with exposed thermal pad (LP suffix) and are supplied in tape and reel.
Are the A3977SLPTR-T and A3977KLPTR pin-compatible?
Yes. Both devices use the same 28-lead TSSOP package with exposed thermal pad (LP package designation) and share an identical pinout. This allows them to be used interchangeably on the same PCB footprint, provided the application's temperature requirements are satisfied by the selected grade.
Can the A3977SLPTR-T and A3977KLPTR be used interchangeably in a design?
They can be used interchangeably only if the application's operating temperature range falls within the A3977SLPTR-T's -20°C to +85°C limit. For applications requiring operation below -20°C or above +85°C, the A3977KLPTR must be used because it is rated for -40°C to +125°C. Electrical parameters and functional behavior are otherwise equivalent between the two grades.
What are the key electrical specifications common to both devices?
Both the A3977SLPTR-T and A3977KLPTR share the same core specifications: 8 V to 35 V supply voltage range, up to 2.5 A output current per winding, internal DMOS output drivers with synchronous rectification, built-in translator for full-, half-, quarter-, and eighth-step operation, and logic supply voltage of 3.0 V to 5.5 V. They also include internal PWM current control, fixed off-time, and thermal shutdown protection.
What package do the A3977SLPTR-T and A3977KLPTR use?
Both devices are supplied in a 28-lead TSSOP package with an exposed thermal pad, designated by the "LP" suffix in the part number. The package is RoHS-compliant and is provided in tape and reel format, as indicated by the "TR" suffix in the A3977SLPTR-T part number.
Which grade should be selected for automotive or industrial applications?
For applications requiring operation below -20°C or above +85°C, the A3977KLPTR with its -40°C to +125°C temperature range should be selected. The A3977SLPTR-T is suitable for applications operating within -20°C to +85°C. Designers should verify the specific temperature requirements of their application against the manufacturer's datasheet before making a selection.
Do both devices support microstepping operation?
Yes. Both the A3977SLPTR-T and A3977KLPTR support full-step, half-step, quarter-step, and eighth-step microstepping modes. The microstep resolution is selected via the MS1 and MS2 logic inputs, and the built-in translator handles the step sequencing internally, requiring only a step pulse and direction signal from the controller.