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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Motor Drivers, Controllers

Allegro MicroSystems A8904SLBTR-T

Name: A8904SLBTR-T
Brand: Allegro MicroSystems
SKU: A8904SLBTR-T
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: A8904SLBTR-T

Manufacturer:: Allegro MicroSystems

Category:: Motor Drivers, Controllers

Package:: 24-SOIC (0.295", 7.50mm Width)

Datasheet:: A8904SLBTR-T.pdf

Description:: IC MOTOR DRIVER 4.5V-5.5V 24SOIC

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Product details

Overview

A8904SLBTR-T from Allegro MicroSystems is a 3-phase brushless DC motor controller/driver with integrated back-EMF sensing, sensorless commutation, and programmable digital frequency-locked loop (FLL) speed control. It delivers up to 1.2 A per phase via low-R_DS(on) N-channel DMOS half-bridges, supports serial configuration of start-up current limit, direction, sleep mode, and diagnostics, and operates from 4.0–14 V_BB and 4.5–5.5 V_DD. It is used in high-speed spindle control for optical drives and precision cooling fans.

For engineers reviewing the A8904SLBTR-T datasheet, A8904SLBTR-T pinout, A8904SLBTR-T application, or A8904SLBTR-T equivalent, key selection criteria include its 24-pin SOICW (LB) package with fused thermal leads, programmable transconductance gain (250/500 mA/V), 3.3 MHz serial port interface, adaptive commutation delay, and real-time diagnostic data output via DATA OUT multiplexer.

Technical Context

The A8904SLBTR-T implements sensorless commutation using adaptive back-EMF zero-crossing detection at the high-impedance output terminal, synchronized by FCOM toggling and controlled by CD1/CD2 timing capacitors. Its linear current-mode control loop uses FILTER terminal voltage to drive low-side MOSFETs with transconductance gain selectable via D28.

It integrates a programmable watchdog timer (CWD), start-up oscillator (CST), charge pump for high-side gate drive, and dynamic braking via BRAKE pin or serial port command. The device features undervoltage lockout (3.6–3.9 V), thermal shutdown (165 °C), and overcurrent protection configurable through D3/D4 bits.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Current	±1.2 A continuous per phase - enables direct driving of mid-power BLDC motors without external gate drivers
r_DS(on)	1.0 Ω typical (source + sink + RS) - minimizes conduction loss and thermal rise in 24-pin SOICW package
V_BB Range	4.0–14 V - supports 5 V and 12 V motor supplies common in optical disc drives and fan modules
V_DD Range	4.5–5.5 V - ensures compatibility with standard 5 V logic rails and robust operation across supply tolerance
Serial Clock Max	3.3 MHz - allows fast parameter reconfiguration during runtime without MCU timing constraints
Transconductance Gain	250 mA/V or 500 mA/V (D28-selectable) - adjusts current sensitivity to match motor winding resistance and torque requirements
FLL Oscillator	Up to 20 MHz - provides high-resolution speed reference for precise RPM regulation in high-speed applications
Thermal Shutdown	165 °C with 20 °C hysteresis - protects against sustained overload while allowing brief peak-current operation

Pinout & Package

The A8904SLBTR-T is supplied in a 24-pin wide-body SOIC package (LB) with 4 internally fused leads for enhanced thermal dissipation and overall height <1.2 mm. Lead finish is 100% matte tin; RoHS compliant.

Pin	Circuit Role	Design Meaning
1	LOAD SUPPLY (V_BB)	Motor power input (4–14 V); connects to bulk capacitor and high-current traces
2	CD2	Commutation timing capacitor - sets adaptive delay between FCOM transitions for optimal switching timing
3	CWD	Watchdog/blanking capacitor - controls blanking duration during state transitions and prevents false zero-crossing detection
4	CST	Start-up oscillator capacitor - determines initial commutation period before back-EMF lock is achieved
5	OUTA	Phase A half-bridge output - drives one motor winding; sinks or sources current depending on commutation state
6–7	GROUND	Power and logic ground - must be connected to large copper pour for thermal and noise performance
8	OUTB	Phase B half-bridge output - complements OUTA/OUTC in 6-step commutation sequence
9	OUTC	Phase C half-bridge output - completes 3-phase drive; high-impedance during back-EMF sampling
10	CENTERTAP	Motor star-point connection - reference for internal back-EMF comparators; requires low-impedance path
11	BRAKE	Active-low dynamic brake control - short-circuits all windings to ground when asserted; supports external RC timing
12	CRES	Charge reservoir capacitor - stores energy for high-side gate drive and brake circuit operation
13	FILTER	Speed error integrator node - voltage here linearly controls output current; external RC sets loop bandwidth
14	SECTOR DATA	External tachometer input - accepts index/sector pulses for high-precision speed feedback instead of internal FCOM
15	LOGIC SUPPLY (V_DD)	5 V logic rail input - powers internal logic, serial interface, and analog blocks; includes UVLO protection
16	OSCILLATOR	External clock input - drives speed reference counter; supports crystal or MCU-generated clock up to 20 MHz
17	DATA OUT	Multiplexed diagnostic output - selects TACH, FCOM, SYNC, or thermal shutdown status via D22/D23
18–19	GROUND	Additional power/thermal ground pins - mandatory connection to PCB ground plane for thermal management
20	RESET	Active-low sleep enable - clears serial register and forces chip into ultra-low-power mode (250–500 μA)
21	CHIP SELECT	Serial port strobe - active-low enables data latching on CLOCK rising edge; min. high time = 500 ns
22	CLOCK	Serial port clock input - max. 3.3 MHz; synchronizes 29-bit write cycle with MSB-first ordering
23	DATA IN	Serial data input - feeds D28–D0 bits; requires 150 ns setup/hold relative to CLOCK
24	CD1	Second commutation timing capacitor - alternates with CD2 to maintain synchronous delay across all six states

Key Features

Feature	Design Value
Sensorless commutation with adaptive delay	Eliminates Hall sensors or encoders; CD1/CD2 capacitors dynamically adjust commutation timing based on measured back-EMF zero crossings
Programmable transconductance gain	250 mA/V or 500 mA/V selection (D28) enables precise current scaling for diverse motor impedances without hardware change
Real-time diagnostic multiplexing	DATA OUT pin outputs TACH, FCOM, SYNC, or thermal status via serial-configurable 2-bit mux - simplifies system-level fault logging
Dynamic braking control	Brake function activated either externally via BRAKE pin or internally via serial port bit - supports rapid motor stop without mechanical wear
YANK speed-loop initialization	Automatically pulls FILTER to threshold voltage at startup, forcing maximum current until first ERROR FAST signal - ensures reliable spin-up under load
Configurable overcurrent protection	Four current limit levels (125–1400 mA) set by D3/D4 bits - protects windings during stall, start-up, or transient overload

Applications

Optical Disc Drive Spindle Control	High-Speed Cooling Fan Regulation
Use Scenario: Precise constant-RPM rotation of Blu-ray or DVD spindle motors during read/write operations. IC Role / Device Role / Timing Role: Primary motor controller performing sensorless commutation, FLL-based speed regulation, and real-time thermal monitoring. Use Value: Maintains ±0.1% speed stability across temperature and voltage variation, enabling error-free data access and reduced acoustic noise.	Use Scenario: Variable-speed control of server or telecom chassis cooling fans requiring quiet operation and rapid response to thermal load changes. IC Role / Device Role / Timing Role: Closed-loop BLDC driver using external tachometer input (SECTOR DATA) for high-accuracy RPM feedback and dynamic braking for emergency stop. Use Value: Achieves <50 ms speed step response and <30 dB(A) acoustic output via linear current control and optimized commutation timing.
Industrial Pump Motor Control	Medical Imaging Equipment Fans
Use Scenario: Continuous-duty 3-phase BLDC motor driving centrifugal pumps in analytical instrumentation. IC Role / Device Role / Timing Role: Integrated controller handling start-up sequencing, current limiting, and watchdog-protected commutation under varying fluid loads. Use Value: Prevents stalling and overheating via programmable start-up current ramp and adaptive blanking (CWD) during torque transients.	Use Scenario: Ultra-reliable forced-air cooling for MRI or CT scanner detector modules where EMI and failure risk are critical. IC Role / Device Role / Timing Role: Low-noise motor driver using internal back-EMF sensing and serial-port-configurable diagnostics for predictive maintenance. Use Value: Enables >100,000-hour MTBF with real-time thermal shutdown reporting and FCOM-based rotor position validation.

Optical Disc Drive Spindle Control

High-Speed Cooling Fan Regulation

Use Scenario: Precise constant-RPM rotation of Blu-ray or DVD spindle motors during read/write operations.

IC Role / Device Role / Timing Role: Primary motor controller performing sensorless commutation, FLL-based speed regulation, and real-time thermal monitoring.

Use Value: Maintains ±0.1% speed stability across temperature and voltage variation, enabling error-free data access and reduced acoustic noise.

Use Scenario: Variable-speed control of server or telecom chassis cooling fans requiring quiet operation and rapid response to thermal load changes.

IC Role / Device Role / Timing Role: Closed-loop BLDC driver using external tachometer input (SECTOR DATA) for high-accuracy RPM feedback and dynamic braking for emergency stop.

Use Value: Achieves <50 ms speed step response and <30 dB(A) acoustic output via linear current control and optimized commutation timing.

Industrial Pump Motor Control

Medical Imaging Equipment Fans

Use Scenario: Continuous-duty 3-phase BLDC motor driving centrifugal pumps in analytical instrumentation.

IC Role / Device Role / Timing Role: Integrated controller handling start-up sequencing, current limiting, and watchdog-protected commutation under varying fluid loads.

Use Value: Prevents stalling and overheating via programmable start-up current ramp and adaptive blanking (CWD) during torque transients.

Use Scenario: Ultra-reliable forced-air cooling for MRI or CT scanner detector modules where EMI and failure risk are critical.

IC Role / Device Role / Timing Role: Low-noise motor driver using internal back-EMF sensing and serial-port-configurable diagnostics for predictive maintenance.

Use Value: Enables >100,000-hour MTBF with real-time thermal shutdown reporting and FCOM-based rotor position validation.

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-phase BLDC controller applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
A8902CLBA	Pin-for-pin compatible; lacks serial port, fixed transconductance (500 mA/V), no YANK feature, no DATA OUT multiplexer	Targeted at cost-sensitive, fixed-function BLDC applications without need for runtime reconfiguration or diagnostics	Select A8902CLBA only if serial programming, diagnostic visibility, or adaptive startup are not required
DRV10983ZRTVT	TI device with integrated MOSFETs (1.5 A), I²C interface, built-in LDO, but no external tachometer input or sector mode support	Designed for compact, self-contained fan modules; lacks SECTOR DATA and external speed control flexibility	Choose DRV10983ZRTVT when board space is constrained and integrated power stage is preferred over discrete DMOS drivers

Compared with A8902CLBA, the A8904SLBTR-T adds full serial configurability, real-time diagnostics, and adaptive startup - making it suitable for field-upgradable systems. Against DRV10983ZRTVT, it offers superior external feedback integration and higher design flexibility at the cost of requiring external MOSFETs and layout attention to thermal grounding.

Availability

A8904SLBTR-T is available at Aetrix Electronics and suitable for optical disc drives, industrial cooling systems, and medical imaging equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for A8904SLBTR-T includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Allegro MicroSystems is a U.S.-based designer of high-performance magnetic sensing and power IC solutions, founded in 1989 and headquartered in Worcester, Massachusetts.

The A8904 product line delivers integrated 3-phase BLDC motor controllers with sensorless commutation for high-reliability, high-speed applications including data storage, industrial automation, and precision thermal management.

FAQ

What is the maximum continuous output current rating of the A8904SLBTR-T?

The A8904SLBTR-T supports up to ±1.2 A continuous output current per phase under typical operating conditions (T_A = 25°C, 4-layer PCB). This rating assumes proper thermal management using the fused ground leads and adequate copper area. Peak braking current reaches ±3.0 A for ≤800 ms, limited by junction temperature not to exceed 150°C. Actual current capability depends on ambient temperature, PCB layout, and duty cycle - refer to R_θJA = 35°C/W (4-layer) in thermal characteristics.

How does the A8904SLBTR-T achieve sensorless commutation without Hall effect sensors?

The A8904SLBTR-T performs sensorless commutation by monitoring back-EMF voltage at the high-impedance motor winding terminal and comparing it to the centertap (CENTERTAP) voltage. When a zero-crossing is detected, the FCOM signal toggles, triggering an adaptive delay (set by CD1/CD2 capacitors) before the next commutation. This eliminates external position sensors while maintaining synchronization across speed ranges - validated in optical spindle and fan applications per Allegro's functional description.

Can the A8904SLBTR-T be used with an external tachometer signal instead of internal back-EMF sensing?

Yes, the A8904SLBTR-T supports external speed feedback via the SECTOR DATA pin. When D19 = 1 is programmed via the serial port, the device accepts index or sector pulses from an external encoder or disk, generating TACH from those inputs instead of internal FCOM. This mode enables higher speed accuracy in applications like precision metrology tools where mechanical jitter affects back-EMF zero-crossing detection.

What is the purpose of the CWD capacitor on the A8904SLBTR-T, and how is its value selected?

The CWD capacitor sets blanking duration during commutation transients and defines watchdog timeout. During each state transition, CWD charges to V_TL (250 mV) to suppress false back-EMF detection; if no valid zero-crossing occurs before reaching V_TH (2.5 V), watchdog commutation triggers. Value selection requires measuring diode conduction time (t_d) in step mode: CWD = I_CWD × t_d / V_TL. Start-up I_CWD is programmable via D26/D27 bits to accommodate varying motor inductance.

Does the A8904SLBTR-T support dynamic braking, and how is it activated?

Yes, the A8904SLBTR-T supports dynamic braking via two independent methods: (1) asserting the BRAKE pin low (active-low), which turns on all three sink drivers to short motor windings to ground; (2) setting the brake bit (D29) in the serial port. Both methods engage the same internal circuitry. External RC on the BRAKE pin allows adjustable brake delay, while serial control enables software-triggered braking synchronized with system events - confirmed in Functional Description section and Terminal Functions table.

A8904SLBTR-T Specifications

Product attributes: Attribute value

Manufacturer:: Allegro MicroSystems

Series:: -

Package/Case:: 24-SOIC (0.295", 7.50mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Motor Type - Stepper:: -

Motor Type - AC, DC:: Brushless DC (BLDC)

Function:: Controller - Commutation, Direction Management

Output Configuration:: Pre-Driver - Half Bridge (3)

Interface:: SPI

Technology:: CMOS, DMOS

Step Resolution:: -

Applications:: General Purpose

Current - Output:: -

Voltage - Supply:: 4.5V ~ 5.5V

Voltage - Load:: 4V ~ 14V

Operating Temperature:: -20°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 24-SOIC

A8904SLBTR-T FAQ

1.How can I place an order for A8904SLBTR-T through Aetrix?

Please submit a Request for Quotation (RFQ) for A8904SLBTR-T on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for A8904SLBTR-T reliable?

The price and inventory of A8904SLBTR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A8904SLBTR-T is usually 5 days.

3.What payment methods are accepted for A8904SLBTR-T?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A8904SLBTR-T transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for A8904SLBTR-T?

A8904SLBTR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your A8904SLBTR-T order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for A8904SLBTR-T?

For technical support, including A8904SLBTR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A8904SLBTR-T requirements.

6.How does Aetrix verify that A8904SLBTR-T is sourced from the original manufacturer or authorized distributors?

All A8904SLBTR-T products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that A8904SLBTR-T meets industry standards.

7.What is the process for return or replacement of A8904SLBTR-T?

All A8904SLBTR-T units undergo pre-shipment inspection (PSI). If there is an issue with A8904SLBTR-T, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The A8904SLBTR-T part is unused and in its original packaging.

Return procedure for A8904SLBTR-T:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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