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Allegro MicroSystems A8498SLJTR-T
- Part No.:
- A8498SLJTR-T
- Manufacturer:
- Allegro MicroSystems
- Package:
- 8-SOIC (0.154", 3.90mm Width) Exposed Pad
- Datasheet:
-
A8498SLJTR-T.pdf
- Description:
- IC REG BUCK ADJ 3A 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,992
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Product details
Overview
A8498SLJTR-T from Allegro MicroSystems is a wide-input, current-mode buck regulator with integrated 450 mΩ DMOS switch, supporting 8–50 V input and delivering up to 3 A at adjustable 0.8–24 V output; features fixed off-time control, internal soft start (10 ms), thermal shutdown (165°C), and operates in continuous/discontinuous conduction modes for industrial power conversion.
For engineers reviewing the A8498SLJTR-T datasheet, A8498SLJTR-T pinout, A8498SLJTR-T application, or A8498SLJTR-T equivalent, this page delivers verified electrical specs, validated SOIC-LJ package layout, real-world efficiency curves (up to 89% at 3 A), thermal resistance (35°C/W), and design-critical parameters including FB reference (0.8 V ±2%), TSET-based off-time tuning, and VBIAS biasing strategy for 3.3–5 V outputs.
Technical Context
The A8498SLJTR-T implements fixed off-time, current-mode control with internal ramp generation and cycle-skipping at light load; blanking time is 200 ns to suppress diode reverse-recovery transients. It uses external TSET resistor (e.g., 63.4 kΩ) to set off-time (7 µs at VBIAS = 5 V), enabling predictable frequency scaling across input/output ratios.
Feedback is referenced to a precision 0.8 V ±2% internal bandgap; output voltage is set via resistive divider (e.g., R1 = 6.34 kΩ, R2 = 2 kΩ for 3.3 V). VBIAS connects to VOUT during normal operation when VOUT is 3.3–5 V, reducing quiescent current and improving system efficiency versus VIN-biasing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 8–50 V - supports 12 V automotive, 24/36 V industrial buses, and 42 V battery systems without external pre-regulation |
| Output Current | 3 A continuous - limited by thermal design; peak current limit is 3.5 A minimum, enabling robust transient response |
| Feedback Reference | 0.8 V ±2% - enables accurate output regulation from 0.8 V to 24 V using standard resistor tolerances |
| Switch RDS(on) | 450 mΩ @ 25°C - defines conduction loss and thermal rise; increases to 650 mΩ at 125°C junction temperature |
| Thermal Resistance | 35°C/W (RθJA) - measured on 4-layer PCB; requires exposed pad soldering and thermal vias for full 3 A capability |
| Soft Start Time | 10 ms nominal - limits inrush current during startup; triggered by ENB falling edge, VIN > 6 V, or TSD recovery |
| UVLO Threshold | 6.9 V (±0.3 V) with 0.9 V hysteresis - prevents erratic operation during brown-out; ensures clean enable/disable behavior |
Pinout & Package
Package: 8-lead SOIC with exposed thermal pad (suffix LJ); 6.00 × 4.90 mm body, 1.75 mm height, JEDEC MS-012BA compliant; thermal pad must be soldered for rated 3 A operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - BOOT | Gate drive boost node | Charges high-side gate driver bootstrap capacitor; requires 0.01 µF ceramic capacitor between BOOT and LX |
| 2 - ENB | Enable logic input | Active-low enable; pulled low to start soft start; open-circuit disables output and discharges VOUT |
| 3 - TSET | Fixed off-time programming | Resistor to GND sets tOFF (e.g., 63.4 kΩ → ~7 µs at VBIAS = 5 V); critical for stable operation at high VIN/VOUT ratios |
| 4 - GND | Power and signal ground | Common return for feedback, bias, and switching paths; must connect directly to thermal pad for thermal performance |
| 5 - FB | Feedback input | Monitors output via resistor divider; internal 0.8 V reference enables precise VOUT setting (e.g., 3.3 V = 0.8 × (1 + 6.34k/2k)) |
| 6 - VBIAS | Bias supply input | Connected to VOUT when 3.3–5 V output is used; reduces quiescent current vs. VIN biasing and improves efficiency |
| 7 - LX | Switching node | Connects to inductor and catch diode anode; high dv/dt node requiring tight layout and minimized trace area |
| 8 - VIN | Main power input | Accepts 8–50 V; requires local 0.22 µF ceramic + 220 µF electrolytic input capacitance for stability and ripple suppression |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 450 mΩ DMOS switch | Eliminates need for external high-side MOSFET; reduces BOM count and layout complexity in space-constrained designs |
| Adjustable 0.8–24 V output | Supports single IC across multiple rail requirements (e.g., 3.3 V, 5 V, 12 V) using only two external resistors |
| VBIAS-powered biasing | Improves efficiency by 5–10% over VIN-biased operation when VOUT is ≥3.3 V; no power sequencing required |
| Thermal shutdown with hysteresis | Shuts down at 165°C and recovers at 150°C; prevents latch-up and enables automatic restart after cooling |
| Current-mode control with blanking | 200 ns blanking window rejects diode reverse-recovery noise, ensuring stable current sensing in discontinuous mode |
Applications
| Industrial 24 V Bus Converter | Automotive Telematics Power |
|---|---|
|
Use Scenario: Converting 24 V rail to 3.3 V for microcontrollers and sensors in factory automation PLCs. IC Role / Device Role / Timing Role: Primary step-down regulator providing regulated 3.3 V/3 A with high input voltage tolerance and thermal robustness. Use Value: Eliminates need for cascaded converters; 35°C/W thermal resistance enables operation at 85°C ambient with minimal heatsinking. |
Use Scenario: Powering GPS/GSM modules in vehicle telematics units with 9–16 V battery input and 42 V load-dump protection. IC Role / Device Role / Timing Role: Input-tolerant buck controller handling transient overvoltage events while maintaining stable 3.3 V output. Use Value: UVLO (6.9 V) and 50 V absolute max VIN ensure reliable operation during cold-crank and load-dump conditions. |
| POS Terminal Power Supply | Lead-Acid Battery Charger Auxiliary Rail |
|
Use Scenario: Generating 5 V and 3.3 V rails from 12 V input in retail point-of-sale terminals with space constraints. IC Role / Device Role / Timing Role: Compact, SOIC-LJ packaged regulator delivering dual-rail capability via resistor reconfiguration. Use Value: Adjustable output and small footprint reduce board area vs. fixed-output alternatives; supports firmware-upgradable voltage levels. |
Use Scenario: Providing isolated 3.3 V logic power from main 42 V charger output in uninterruptible power supplies. IC Role / Device Role / Timing Role: Secondary regulator decoupling control circuitry from high-current charging path. Use Value: High-efficiency operation (>88% at 3 A) minimizes heat in sealed enclosures; cycle-skipping maintains regulation at standby loads. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5164QDDARQ1 | 42 V max VIN, 0.5 A output, integrated FET, 1.5 MHz fixed-frequency; no VBIAS pin or adjustable off-time | Lower current rating; suited for low-power automotive modules where high switching frequency reduces filter size | Select LM5164QDDARQ1 when <1 A output and compact EMI filtering are prioritized over raw current capability |
| MP2451DT-LF-Z | 36 V max VIN, 0.6 A output, 2 MHz fixed frequency, no thermal pad; 0.8 V FB reference same as A8498SLJTR-T | Limited to lower input voltages and currents; lacks exposed pad and high-current capability for industrial use | Choose MP2451DT-LF-Z only for cost-sensitive, low-power consumer applications with ≤24 V input |
Compared with LM5164QDDARQ1 and MP2451DT-LF-Z, the A8498SLJTR-T uniquely delivers 3 A output with 50 V input tolerance, SOIC-LJ thermal pad support, and VBIAS optimization-making it the sole option among the three for 3 A industrial or automotive 12/24/42 V bus conversion.
Availability
A8498SLJTR-T is available at Aetrix Electronics and suitable for industrial automation, automotive telematics, and POS terminal designs requiring stable component supply, long-term lifecycle assurance, and consistent parametric performance across production batches.
Supply support for A8498SLJTR-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 power ICs and magnetic sensors, headquartered in Manchester, NH, serving automotive, industrial, and consumer markets since 1989.
The A8498 product line targets high-input-voltage DC/DC conversion in harsh environments-designed specifically for reliability under wide VIN ranges (8–50 V), thermal stress, and automotive transients.
FAQ
What is the maximum input voltage rating for the A8498SLJTR-T?
The A8498SLJTR-T has an absolute maximum input voltage rating of 50 V on the VIN pin, with recommended operating range of 8–50 V. This allows direct use with 42 V battery systems and industrial 36 V buses without pre-regulation. Exceeding 50 V risks permanent damage, and the UVLO threshold (6.9 V) ensures safe startup only above functional input levels. The A8498SLJTR-T datasheet specifies these limits under Absolute Maximum Ratings.
How does the A8498SLJTR-T achieve thermal management at 3 A output?
The A8498SLJTR-T relies on its exposed thermal pad in the SOIC-LJ package and specified 35°C/W junction-to-ambient thermal resistance on a 4-layer PCB. To sustain 3 A continuously, the thermal pad must be soldered to a copper plane with ≥4 thermal vias (0.3 mm diameter, spaced ≤1 mm apart). Without proper pad connection, junction temperature exceeds 150°C under full load, triggering thermal shutdown. The A8498SLJTR-T thermal characteristics are validated per JEDEC JESD51-5.
Can the A8498SLJTR-T operate with VOUT below 3.3 V, and what is the impact on biasing?
Yes, the A8498SLJTR-T supports output voltages as low as 0.8 V using the FB divider. However, VBIAS must not be connected to VOUT if VOUT < 3.3 V, because internal bias circuitry cannot regulate properly below that threshold. In such cases, the A8498SLJTR-T draws bias current from VIN, increasing quiescent current (up to 6.35 mA) and reducing efficiency. The A8498SLJTR-T datasheet explicitly recommends VIN biasing for sub-3.3 V outputs.
What is the purpose of the TSET pin on the A8498SLJTR-T, and how is it configured for 3.3 V output?
The TSET pin sets the fixed off-time using a resistor to GND; for a 42 V → 3.3 V conversion, the recommended value is 63.4 kΩ, yielding ~7 µs off-time at VBIAS = 5 V. This ensures minimum on-time is not violated and prevents cycle-skipping instability. The A8498SLJTR-T datasheet provides the formula tOFF = (10.2 × 10⁹)/(1 – 0.03 × VBIAS)/RTSET, and confirms 63.4 kΩ is validated for this specific application in the Recommended Components table.
Does the A8498SLJTR-T include built-in protection features, and how do they behave during fault conditions?
Yes, the A8498SLJTR-T integrates VIN undervoltage lockout (6.9 V), thermal shutdown (165°C), and short-circuit protection. During a short, FB voltage drops below 0.4 V, triggering a reduced 1.5 A current limit and extended off-time (up to 8× nominal) to prevent switch failure. After thermal shutdown, the A8498SLJTR-T automatically restarts with soft start once junction temperature falls 15°C below trip point. All protections are fully documented in the A8498SLJTR-T Electrical Characteristics and Functional Description sections.
A8498SLJTR-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:
- 3A
- Frequency - Switching:
- -
- Synchronous Rectifier:
- No
- Operating Temperature:
- -20°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC-EP
A8498SLJTR-T FAQ
1.How can I place an order for A8498SLJTR-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A8498SLJTR-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 A8498SLJTR-T reliable?
The price and inventory of A8498SLJTR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A8498SLJTR-T is usually 5 days.
3.What payment methods are accepted for A8498SLJTR-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A8498SLJTR-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A8498SLJTR-T?
A8498SLJTR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A8498SLJTR-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 A8498SLJTR-T?
For technical support, including A8498SLJTR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A8498SLJTR-T requirements.
6.How does Aetrix verify that A8498SLJTR-T is sourced from the original manufacturer or authorized distributors?
All A8498SLJTR-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 A8498SLJTR-T meets industry standards.
7.What is the process for return or replacement of A8498SLJTR-T?
All A8498SLJTR-T units undergo pre-shipment inspection (PSI). If there is an issue with A8498SLJTR-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 A8498SLJTR-T part is unused and in its original packaging.
Return procedure for A8498SLJTR-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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