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Allegro MicroSystems A4447SLJTR-T
- Part No.:
- A4447SLJTR-T
- Manufacturer:
- Allegro MicroSystems
- Package:
- 8-SOIC (0.154", 3.90mm Width) Exposed Pad
- Datasheet:
-
A4447SLJTR-T.pdf
- Description:
- IC REG BUCK ADJ 2A 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:19,153
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Product details
Overview
A4447SLJTR-T from Allegro MicroSystems is a high-voltage, 2 A synchronous stepdown regulator in an 8-pin SOIC package with exposed thermal pad. It operates across 8–50 V input, delivers adjustable 0.8–24 V output, features fixed off-time current-mode control, integrated 450 mΩ DMOS switch, and supports light-load cycle-skipping for regulation down to zero load. It is used in industrial power supplies, POS terminals, and 24/36 V bus systems.
For engineers reviewing the A4447SLJTR-T datasheet, A4447SLJTR-T pinout, A4447SLJTR-T application, or A4447SLJTR-T equivalent, this page provides verified technical context, validated pin functions, confirmed thermal resistance (RθJA = 35 °C/W on 4-layer PCB), real-world efficiency curves up to 2 A, and accurate alternative selection guidance based on functional equivalence and package compatibility.
Technical Context
The A4447SLJTR-T implements fixed off-time, current-mode control with internal blanking (200 ns) to suppress diode reverse-recovery transients at the LX node. Its TSET pin sets off-time via external resistor (e.g., 54 kΩ yields ~110 µs at VBIAS = 3.3 V), enabling stable operation across wide VIN/VOUT ratios.
It integrates a 450 mΩ (typ.) buck switch, 0.8 V ±2% reference, and dual-stage overcurrent protection: 2.2 A limit for normal operation and 0.85 A limit when FB falls below 0.4 V. Bias supply routing (VBIAS tied to VOUT for 3.3–5 V outputs) improves system efficiency by reducing VIN-derived quiescent current from 4.4 mA to 0.9 mA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 8–50 V - Supports 24 V and 36 V industrial bus rails without pre-regulation. |
| Output Current | 2 A continuous - Sustained delivery under full load with proper thermal layout (RθJA = 35 °C/W). |
| Output Voltage Range | 0.8–24 V - Set by resistor divider; 0.8 V reference enables low-VOUT designs (e.g., 1.5 V, 1.8 V, 3.3 V). |
| Switch RDS(on) | 450 mΩ (typ. at 25°C) - Limits conduction loss; rises to 650 mΩ at 125°C, requiring thermal derating. |
| Feedback Reference | 0.8 V ±2% - Enables ±3% output regulation accuracy across 0–2 A load range. |
| Fixed Off-Time Control | Adjustable via RTSET (7.65–105 kΩ) - Sets switching frequency inversely; e.g., 54 kΩ → ~110 µs off-time → ~123 kHz at VIN=42 V, VOUT=5 V. |
| Thermal Shutdown | 165°C (±15°C hysteresis) - Protects against sustained overload or inadequate heatsinking. |
Pinout & Package
Package: 8-pin SOIC (LJ) with exposed thermal pad; leadframe plating 100% matte tin; footprint per IPC-7351 SOIC127P600X175-9AM.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - BOOT | Gate drive boost node | Charges bootstrap capacitor to enable high-side gate drive; requires 0.01 µF ceramic capacitor to LX. |
| 2 - ENB | On/off control input | Active-low logic enable; open-circuit disables output; falling edge triggers soft-start sequence. |
| 3 - TSET | Off-time setting | Resistor-to-ground sets fixed off-time; minimum 7.65 kΩ required to avoid violating minimum on-time. |
| 4 - GND | Power and signal ground | Star-ground connection point; must tie exposed thermal pad directly to large copper area via thermal vias. |
| 5 - FB | Feedback input | Senses output voltage via resistor divider; 0.8 V reference enables precise VOUT programming (e.g., 3.3 V with R1=2.87 kΩ, R2=0.91 kΩ). |
| 6 - VBIAS | Bias supply input | Connected to VOUT for 3.3–5 V outputs to reduce quiescent current; left open for VOUT < 3.3 V. |
| 7 - LX | Buck switching node | Connects to inductor and Schottky catch diode cathode; high dV/dt node requiring short, low-inductance routing. |
| 8 - VIN | Main supply input | Accepts 8–50 V; requires local 0.22 µF + bulk electrolytic (e.g., 100 µF/50 V) placed adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| Wide input range (8–50 V) | Eliminates need for pre-regulators in 24 V/36 V industrial and POS systems. |
| Integrated 450 mΩ DMOS switch | Reduces BOM count and board space vs. controller + external MOSFET solutions. |
| Adjustable fixed off-time | Enables predictable frequency behavior across input/output combinations without loop compensation redesign. |
| Internal 200 ns blanking circuit | Suppresses false triggering from Schottky diode reverse recovery, improving reliability in high-dV/dt layouts. |
| Exposed thermal pad (LJ package) | Enables RθJP = 2 °C/W to PCB copper, critical for sustaining 2 A continuous current at 85°C ambient. |
Applications
| Industrial 24 V Bus Power | POS Thermal Printer Supply |
|---|---|
|
Use Scenario: Power conversion from 24 V rail to 3.3 V logic supply in factory automation controllers. IC Role / Device Role / Timing Role: Primary stepdown regulator delivering regulated 3.3 V at up to 2 A to microcontroller, sensors, and interface ICs. Use Value: High efficiency (>85% at 2 A) minimizes heat buildup in sealed enclosures; wide VIN accommodates brownout conditions. |
Use Scenario: Compact DC-DC stage powering thermal print head drivers and logic in retail point-of-sale terminals. IC Role / Device Role / Timing Role: Adjustable-output buck converter set to 5 V or 3.3 V, supporting variable load profiles during print cycles. Use Value: Cycle-skipping mode maintains tight regulation at standby current (<10 mA); small SOIC-LJ footprint fits tight mechanical envelopes. |
| Uninterruptible Power Supply (UPS) | Tape Drive Motor & Logic Supply |
|
Use Scenario: Secondary regulation stage converting 42 V battery-backed bus to 1.8 V/3.3 V for UPS control electronics. IC Role / Device Role / Timing Role: High-input-voltage buck regulator with UVLO (6.9 V) ensuring clean shutdown before battery depletion. Use Value: 50 V absolute max VIN rating allows direct connection to 42 V nominal battery stack; thermal shutdown prevents damage during overload events. |
Use Scenario: Dual-rail generation (5 V for motor driver, 3.3 V for FPGA) in enterprise tape backup drives. IC Role / Device Role / Timing Role: Single-chip solution replacing discrete regulators; uses same layout for multiple VOUT configurations via FB divider change. Use Value: RTSET-based off-time tuning allows optimization for different inductor values; CBYP capacitor option improves transient response to motor startup surges. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2451DJ-LF-Z | 36 V max VIN, 0.5 A output, no exposed thermal pad, fixed 520 kHz frequency | Limited to lower-power applications; unsuitable for 2 A loads or >36 V inputs | Select only for cost-sensitive, low-current designs where 36 V VIN ceiling is acceptable. |
| LM5164QDDARQ1 | Automotive-grade (AEC-Q100), 100 V max VIN, 1 A output, integrated high-side FET, spread-spectrum EMI reduction | Designed for automotive environments; higher VIN capability but lower current rating than A4447SLJTR-T | Prefer for automotive infotainment or ADAS power rails; not drop-in due to different pinout and thermal requirements. |
Compared with MP2451DJ-LF-Z and LM5164QDDARQ1, the A4447SLJTR-T uniquely balances 50 V input capability, 2 A output, SOIC-LJ thermal performance, and adjustable off-time-making it optimal for industrial and POS systems requiring robust, medium-power DC-DC conversion without automotive qualification overhead.
Availability
A4447SLJTR-T is available at Aetrix Electronics and suitable for industrial automation, point-of-sale equipment, and uninterruptible power supplies requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for A4447SLJTR-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 semiconductor company specializing in high-performance power ICs, magnetic sensors, and precision motion-control solutions.
The A4447 product line delivers high-voltage, high-efficiency buck regulators optimized for industrial, commercial, and POS applications where wide input range, thermal robustness, and design simplicity are critical.
FAQ
What is the maximum input voltage rating for the A4447SLJTR-T?
The A4447SLJTR-T has an absolute maximum input voltage rating of 50 V, with guaranteed operation across 8–50 V. This enables direct use with 24 V, 36 V, and 42 V industrial bus systems. Exceeding 50 V risks permanent damage; the internal UVLO threshold is 6.9 V (typ.), ensuring safe startup above 6.6 V and shutdown before reaching destructive levels.
How does the A4447SLJTR-T achieve thermal stability at 2 A continuous output?
The A4447SLJTR-T achieves thermal stability at 2 A through its exposed thermal pad (LJ package) and low RθJP of 2 °C/W. When mounted on a 4-layer PCB with adequate copper area and thermal vias, its RθJA is 35 °C/W - allowing junction temperature to remain below 150 °C at 85 °C ambient. Derating is required above 85 °C ambient or with insufficient copper.
Can the A4447SLJTR-T be used to generate 1.5 V output?
Yes, the A4447SLJTR-T can generate 1.5 V output using the FB resistor divider. With a 0.8 V reference, R1 = 1.30 kΩ and R2 = 1.47 kΩ yield 1.5 V (VOUT = 0.8 × (1 + 1.30/1.47)). The device maintains ±3% regulation across 0–2 A load, and light-load cycle-skipping ensures stability even at microamp-level currents.
What is the purpose of the VBIAS pin on the A4447SLJTR-T?
The VBIAS pin on the A4447SLJTR-T supplies bias current to internal circuitry. When VOUT is between 3.3 V and 5 V, connecting VBIAS to VOUT reduces VIN-sourced quiescent current from 4.4 mA to 0.9 mA - improving system efficiency. For VOUT < 3.3 V, VBIAS is left open and bias is drawn from VIN, accepting a modest efficiency penalty.
Does the A4447SLJTR-T require an external Schottky diode?
Yes, the A4447SLJTR-T requires an external Schottky catch diode (e.g., NSQ03A06) connected from LX to GND. It is not a synchronous rectifier IC - the internal DMOS switch operates as a high-side buck transistor only. The diode handles freewheeling current during the off-time; its voltage rating must exceed the maximum expected VIN (e.g., ≥60 V for 42 V input).
A4447SLJTR-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 8V
- Voltage - Input (Max):
- 50V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 24V
- Current - Output:
- 2A
- Frequency - Switching:
- -
- Synchronous Rectifier:
- No
- Operating Temperature:
- -20°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC-EP
A4447SLJTR-T FAQ
1.How can I place an order for A4447SLJTR-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A4447SLJTR-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 A4447SLJTR-T reliable?
The price and inventory of A4447SLJTR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A4447SLJTR-T is usually 5 days.
3.What payment methods are accepted for A4447SLJTR-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A4447SLJTR-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A4447SLJTR-T?
A4447SLJTR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A4447SLJTR-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 A4447SLJTR-T?
For technical support, including A4447SLJTR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A4447SLJTR-T requirements.
6.How does Aetrix verify that A4447SLJTR-T is sourced from the original manufacturer or authorized distributors?
All A4447SLJTR-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 A4447SLJTR-T meets industry standards.
7.What is the process for return or replacement of A4447SLJTR-T?
All A4447SLJTR-T units undergo pre-shipment inspection (PSI). If there is an issue with A4447SLJTR-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 A4447SLJTR-T part is unused and in its original packaging.
Return procedure for A4447SLJTR-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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