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Allegro MicroSystems A8697ELJTR-T
- Part No.:
- A8697ELJTR-T
- Manufacturer:
- Allegro MicroSystems
- Package:
- 8-SOIC (0.154", 3.90mm Width) Exposed Pad
- Datasheet:
-
A8697ELJTR-T.pdf
- Description:
- IC REG BUCK ADJ 4A 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,300
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Product details
Overview
A8697ELJTR-T from Allegro MicroSystems is a wide-input, constant off-time current-mode synchronous buck regulator with integrated 180 mΩ DMOS switch, supporting 8–25 V input and delivering up to 4.0 A at adjustable output voltages down to 0.8 V; used in 12 V automotive accessory power supplies and point-of-sale systems requiring compact, thermally robust DC/DC conversion.
For engineers reviewing the A8697ELJTR-T datasheet, A8697ELJTR-T pinout, A8697ELJTR-T application, or A8697ELJTR-T equivalent, this page delivers verified electrical parameters, thermal package data, functional block context, real-world load transient behavior, and validated alternative options for legacy design continuity.
Technical Context
The A8697ELJTR-T implements fixed off-time current-mode control with internal ramp generation and blanking (200 ns) to suppress diode reverse-recovery noise. It operates in both continuous and discontinuous conduction modes and enters cycle-skipping mode under light load to maintain regulation.
Off-time is resistor-programmable via TSET (5–16 μs range), enabling flexible inductor selection; soft-start time is 10 ms nominal with 3.5 A minimum current limit during ramp-up. Bias is supplied from VOUT (3.3–5 V recommended) or VIN, eliminating external bias supply requirements.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 8–25 V - supports unregulated 12 V automotive and industrial bus rails without pre-regulation. |
| Output Current | 4.0 A continuous - rated for full-load operation with proper PCB thermal vias and 4-layer board layout. |
| Feedback Reference | 0.8 V ±2% - enables precise output setting from 0.8 V to 20 V using external resistor divider (VOUT = 0.8 × (1 + R1/R2)). |
| Switch RDS(on) | 180 mΩ typical at 25°C - reduces conduction loss and thermal stress in high-current 12 V→1.06 V conversion. |
| Quiescent Current | 100 μA max when enabled - ensures low standby power in always-on POS or networking applications. |
| Thermal Shutdown | 165°C with 15°C hysteresis - protects against sustained overload or poor heatsinking while allowing safe recovery. |
| UVLO Threshold | 6.9 V ±0.3 V with 0.9 V hysteresis - prevents erratic startup during brownout conditions on 12 V input rails. |
Pinout & Package
Package: 8-lead SOIC with exposed thermal pad (JEDEC MS-012AA, suffix LJ); 6.20 × 5.80 mm body, 1.75 mm height, 0.65 mm lead pitch; thermal pad must be soldered to PCB ground plane with ≥4 thermal vias for 35°C/W θJA performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - BOOT | Gate drive bootstrap node | Charges high-side gate driver capacitor; requires 0.01 μF ceramic capacitor between BOOT and LX. |
| 2 - ENB | Enable logic input | Active-high (≥2.0 V) enables soft-start; open-circuit disables output and reduces IQ to 100 μA. |
| 3 - TSET | Off-time programming | Resistor to GND sets tOFF (5–16 μs); determines switching frequency and inductor ripple current. |
| 4 - GND | Power and signal ground | Common return for FB, ENB, TSET, and thermal pad; must connect directly to exposed pad. |
| 5 - FB | Feedback input | Compares divided output voltage to 0.8 V reference; bias current <100 nA minimizes resistor-divider error. |
| 6 - VBIAS | Bias supply input | Accepts VOUT (3.3–5 V) to improve efficiency; otherwise draws bias from VIN with efficiency penalty. |
| 7 - LX | Switch node | Connects to inductor and Schottky catch diode anode; high dV/dt node requiring tight layout and ground shielding. |
| 8 - VIN | Main input supply | 8–25 V input with UVLO; requires ≥47 μF bulk capacitance near pin to suppress ripple and EMI. |
| Pad - Exposed Thermal Pad | Thermal dissipation path | Must be soldered to solid copper pour tied to system ground; primary path for heat removal (RθJA = 35°C/W). |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 180 mΩ DMOS switch | Eliminates need for external high-side MOSFET and driver, reducing BOM count and layout area by >30%. |
| Adjustable fixed off-time control | Enables stable operation across wide VIN/VOUT ratios (up to 12.5:1) without loop compensation components. |
| Internal soft-start (10 ms) | Prevents inrush current surges into output capacitors, avoiding input rail collapse during cold start. |
| VBIAS self-bias capability | Allows VOUT to power internal circuitry once regulated, improving full-load efficiency by ~3% vs. VIN biasing. |
| Cycle-skipping light-load mode | Maintains ±3% output regulation at loads as low as 10 mA without external enable sequencing. |
Applications
| Automotive Accessory Power | Point-of-Sale Terminals |
|---|---|
|
Use Scenario: 12 V vehicle battery powers portable DVD player or dashcam with 1.06 V/4 A core rail. IC Role / Device Role / Timing Role: Primary step-down regulator converting noisy, variable 12 V automotive supply to clean, low-noise 1.06 V for SoC core voltage. Use Value: Integrated switch and thermal pad enable compact, fanless design meeting ISO 7637-2 pulse immunity requirements without external FET heatsink. |
Use Scenario: Embedded POS terminal uses 12 V wall adapter to generate 3.3 V/2 A for ARM processor and display interface. IC Role / Device Role / Timing Role: Adjustable buck converter providing stable 3.3 V rail with fast load transient response (<100 μs settling) during barcode scan bursts. Use Value: Cycle-skipping mode maintains regulation at standby currents <50 mA, extending battery backup runtime during AC outage. |
| Networking Equipment | Industrial Control I/O Modules |
|
Use Scenario: 24 V PoE-powered switch supplies 5.0 V/3 A to Ethernet PHY and management MCU. IC Role / Device Role / Timing Role: High-efficiency intermediate regulator stepping 24 V down to 5 V before LDO post-regulation. Use Value: 8–25 V input range accommodates PoE voltage drop across long cables while maintaining >85% efficiency at full load. |
Use Scenario: Programmable logic controller (PLC) module derives 1.8 V/4 A for FPGA configuration and I/O drivers from 24 V field bus. IC Role / Device Role / Timing Role: Robust buck regulator operating in industrial ambient (−40°C to +85°C) with thermal shutdown recovery. Use Value: 165°C thermal shutdown with 15°C hysteresis prevents latch-up during overtemperature events in sealed enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2451DT-LF-Z | Fixed 3.3 V/5 V output only; no adjustable VFB; 2 A max output; smaller TSOT23-6 package. | Limited to fixed-output designs; insufficient for 4 A or sub-3.3 V rails like 1.06 V FPGA cores. | Select only for new low-current, fixed-VOUT designs where footprint and cost outweigh flexibility needs. |
| LM2678SX-5.0/NOPB | 5 V fixed output; 5 A rating; requires external MOSFET; larger TO-263-5 package; no integrated switch. | Higher current capability but adds complexity, layout area, and external component count. | Choose only when 5 V fixed output suffices and thermal design allows TO-263 mounting with external FET. |
Compared with A8697ELJTR-T, MP2451DT-LF-Z lacks adjustable output and 4 A capability, limiting reuse in legacy 1.06 V/4 A designs; LM2678SX-5.0/NOPB offers higher current but requires external FET and cannot replace A8697ELJTR-T without PCB redesign and bill-of-material changes.
Availability
A8697ELJTR-T is available at Aetrix Electronics and suitable for automotive accessory power, point-of-sale terminals, and industrial control I/O modules requiring stable component supply despite end-of-life status.
Supply support for A8697ELJTR-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, founded in 1989 and headquartered in Worcester, MA.
The A8697ELJTR-T belongs to Allegro's wide-input buck regulator product line, engineered for rugged 8–25 V industrial and automotive power conversion where integration, thermal reliability, and input voltage resilience are critical.
FAQ
What is the maximum continuous output current supported by the A8697ELJTR-T?
The A8697ELJTR-T is rated for 4.0 A continuous output current under standard thermal conditions: 4-layer PCB with exposed thermal pad soldered and ≥4 thermal vias, ambient temperature ≤85°C, and input voltage ≤12 V. At higher input voltages or elevated ambient, derating applies per the Maximum Load Current graph in the datasheet; peak current limit is 6.2 A typical.
Can the A8697ELJTR-T operate with an output voltage lower than 0.8 V?
No - the A8697ELJTR-T has a fixed internal feedback reference of 0.8 V ±2%, and its output voltage is calculated as VOUT = 0.8 V × (1 + R1/R2). The lowest achievable output is therefore constrained by resistor tolerance and noise; 0.8 V is the absolute minimum. For sub-0.8 V rails, a different regulator with lower reference voltage is required.
Is the A8697ELJTR-T still in active production or available for new designs?
The A8697ELJTR-T is classified as Last Time Buy (LTB) with final order deadline May 30, 2014. It remains available from Aetrix Electronics for existing customer applications and legacy design continuity, but Allegro does not recommend it for new designs due to obsolescence. Samples are no longer provided.
How does the TSET pin affect switching frequency in the A8697ELJTR-T?
The TSET pin sets the fixed off-time (tOFF) via an external resistor; tOFF ranges from ~5 μs to 16 μs depending on RTSET value and VBIAS. Since tON varies with VIN, VOUT, and load, the resulting switching frequency is not fixed - it decreases as VIN increases or VOUT decreases. For example, at VIN = 12 V, VOUT = 1.06 V, and RTSET = 51.1 kΩ, fSW ≈ 173 kHz.
What is the purpose of the VBIAS pin on the A8697ELJTR-T, and how should it be connected?
The VBIAS pin supplies operating current to internal circuitry. When VOUT is between 3.3 V and 5.0 V, VBIAS should be connected directly to VOUT to improve efficiency. If VOUT < 3.3 V, VBIAS may be left unconnected and the device will draw bias from VIN - though this reduces efficiency. An external 3.3–5 V source may also be used; no power-up sequencing is required.
A8697ELJTR-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:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 8V
- Voltage - Input (Max):
- 25V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 20V
- Current - Output:
- 4A
- Frequency - Switching:
- -
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC-EP
A8697ELJTR-T FAQ
1.How can I place an order for A8697ELJTR-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A8697ELJTR-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 A8697ELJTR-T reliable?
The price and inventory of A8697ELJTR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A8697ELJTR-T is usually 5 days.
3.What payment methods are accepted for A8697ELJTR-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A8697ELJTR-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A8697ELJTR-T?
A8697ELJTR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A8697ELJTR-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 A8697ELJTR-T?
For technical support, including A8697ELJTR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A8697ELJTR-T requirements.
6.How does Aetrix verify that A8697ELJTR-T is sourced from the original manufacturer or authorized distributors?
All A8697ELJTR-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 A8697ELJTR-T meets industry standards.
7.What is the process for return or replacement of A8697ELJTR-T?
All A8697ELJTR-T units undergo pre-shipment inspection (PSI). If there is an issue with A8697ELJTR-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 A8697ELJTR-T part is unused and in its original packaging.
Return procedure for A8697ELJTR-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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