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Analog Devices Inc. LT1082MJ8
- Part No.:
- LT1082MJ8
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-CDIP (0.300", 7.62mm)
- Datasheet:
-
LT1082MJ8.pdf
- Description:
- IC REG BCK BST ADJ 850MA 8CERDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,895
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Product details
Overview
LT1082MJ8 from Linear Technology is a monolithic high-voltage current-mode switching regulator IC with an integrated 1A power switch, 100V switch breakdown voltage, 60kHz switching frequency, 4.5mA quiescent current, and operation from 3V to 75V input. It supports buck, boost, flyback, forward, and inverting topologies and is used in telecom negative-to-positive 5V supplies delivering 0.7A from –48V.
For engineers reviewing the LT1082MJ8 datasheet, LT1082MJ8 pinout, LT1082MJ8 application, or LT1082MJ8 equivalent, key selection considerations include its isolated flyback regulation mode (enabling optocoupler-free floating outputs), shutdown mode drawing only 120µA, short-circuit frequency shift-down to 12kHz, and compatibility with wide-input industrial power conversion designs.
Technical Context
The LT1082MJ8 implements current-mode control where switch duty cycle is directly set by sensed switch current rather than output voltage feedback-delivering fast line transient response and simplified loop compensation. Its internal 1.24V bandgap reference feeds the error amplifier's positive input, while the FB pin serves dual roles: standard voltage feedback and flyback pulse amplitude sensing when IFB = 60–200µA.
It features adaptive anti-saturation driver logic that dynamically adjusts gate drive to minimize switch saturation voltage and enable rapid turn-off. The VC pin provides four functions: frequency compensation node, current limit adjustment point, soft-start interface, and shutdown control-pulling VC below 0.15V reduces supply current to 120µA typical.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 75V - enables direct operation from telecom –48V rails, industrial 24V/48V buses, and wide-range DC inputs without pre-regulation. |
| Switch Breakdown Voltage | 100V - supports flyback and boost topologies with high reflected voltages or high-input applications up to 75V VIN. |
| Switch Current Limit | 1.07A (typ, 20% duty) - sets maximum deliverable power (~20W no-external-FET); reduced linearly above 50% duty cycle for thermal safety. |
| Quiescent Current | 4.5mA (typ) - minimizes no-load power loss in battery-backed or standby-critical systems. |
| Shutdown Supply Current | 120µA (typ) - allows ultra-low-power standby in always-on telecom or remote monitoring equipment. |
| Flyback Reference Voltage | 18.6V (typ, IFB = 60µA) - defines regulated flyback pulse amplitude for isolated output control without optocouplers. |
| Switching Frequency | 60kHz (typ) - balances magnetics size, EMI, and efficiency; externally synchronizable to 75–90kHz. |
| Reference Voltage | 1.244V (typ) - precision bandgap reference enabling accurate output voltage setting via resistor divider on FB pin. |
Pinout & Package
J8 package is an 8-lead hermetic ceramic DIP (0.300" width), rated for TJMAX = 150°C and θJA = 100°C/W. Pin 1–8 are arranged in standard dual-in-line configuration with GND, VC, FB, NC, E2, VSW, E1, VIN sequence (top view).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (GND) | Power ground reference | Common return for internal circuitry and external low-side sensing; connects to PCB ground plane. |
| 2 (VC) | Error amplifier output / control node | Provides compensation network connection, current limit adjustment, soft-start ramp, and shutdown trigger (≤0.15V). |
| 3 (FB) | Feedback input / flyback sense | Accepts voltage divider output for regulation; draws 60–200µA to enable isolated flyback mode. |
| 4 (NC) | No connect | Internally unconnected; must remain floating-no external connection permitted. |
| 5 (E2) | Second emitter of internal switch | Optional connection to reduce switch current limit by ~2×; leaving open doubles RDS(ON) and degrades efficiency above 100mA. |
| 6 (VSW) | Switch collector output | High-voltage switching node connected to transformer primary or inductor; rated for 100V breakdown. |
| 7 (E1) | Primary emitter of internal switch | Must be tied to GND pin (Pin 1); forms main current path with E2 for full 1A capability. |
| 8 (VIN) | Power input supply | Supplies internal LDO (2.3V) and oscillator; accepts 3–75V with minimal performance variation. |
Key Features
| Feature | Design Value |
|---|---|
| Isolated flyback regulation mode | Enables fully floating, optocoupler-free outputs by regulating flyback pulse amplitude-reducing BOM count and improving reliability in telecom/isolated supplies. |
| Short-circuit frequency shift-down | Automatically reduces switching frequency from 60kHz to 12kHz when FB pin sources ≥350µA-preventing minimum-on-time violation and maintaining regulation under hard shorts at high input voltages. |
| Externally synchronized operation | Supports synchronization to 75–90kHz clock via VC pin pull-down-enabling EMI reduction through fixed-frequency coordination in multi-regulator systems. |
| Dual-emitter switch architecture | Separate E1/E2 pins allow user-selectable current limit scaling (1A full or ~0.5A reduced) and improved layout flexibility for ground-referenced sensing. |
| Current-mode control topology | Delivers inherent cycle-by-cycle current limiting, superior line transient response, and simplified loop compensation across wide VIN/VOUT/load ranges. |
| Low-quiescent-current shutdown | Reduces total supply current to 120µA typical-critical for battery-powered or energy-harvesting systems requiring extended standby life. |
Applications
| Telecom Negative-to-Positive 5V Supply | Industrial Wide-Input Boost Converter |
|---|---|
Use Scenario: Generating regulated +5V at 0.7A from a –48V telecom battery bus with high reliability and no optocouplers. IC Role / Device Role / Timing Role: Primary controller implementing flyback topology with isolated regulation via FB pin current sensing; operates at 60kHz base frequency. Use Value: Eliminates optocoupler and secondary-side reference, reducing component count and failure points while maintaining ±2% output accuracy over temperature. | Use Scenario: Stepping up 15V industrial rail to 90V at 120mA for sensor biasing or analog front-end supplies. IC Role / Device Role / Timing Role: Boost regulator controller driving external diode and inductor; uses internal 1A switch and 100V VSW rating for safe high-VOUT operation. Use Value: Achieves >85% efficiency at full load without external MOSFET, simplifying design and lowering bill-of-materials cost. |
| Isolated Dual-Output Flyback Supply | High-Voltage Inverting Regulator |
Use Scenario: Providing isolated ±15V outputs (0.3A each) from a 30–70V input in medical instrumentation requiring reinforced isolation. IC Role / Device Role / Timing Role: Flyback controller using FB pin for primary-side regulation of both outputs; leverages built-in blanking to reject leakage spikes. Use Value: Delivers tightly coupled ±15V outputs with <±5% cross-regulation and <1% load regulation-no post-regulation required. | Use Scenario: Generating –20V at 200mA from a 24V supply for op-amp rails in test equipment. IC Role / Device Role / Timing Role: Inverting topology controller with internal switch and 100V breakdown-supports high |VOUT|/VIN ratios safely. Use Value: Enables compact, single-chip inverter design with 1.24V reference accuracy and 60kHz switching for low-noise output. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1082CN8 | Same die, plastic DIP-8 package; θJA = 90°C/W; commercial temp range (0°C to 100°C). | Lower cost, non-hermetic; unsuitable for high-reliability or extended temperature environments. | Select LT1082CN8 for cost-sensitive commercial designs where hermeticity and extended temperature are not required. |
| LT1082CQ | Same die, 5-lead DD Pak; θJA = 40°C/W; includes exposed copper heat sink pad. | Superior thermal performance; requires PCB thermal pad; incompatible pinout and footprint. | Choose LT1082CQ when higher power density or continuous 1A operation at elevated ambient temperatures is needed. |
Compared with LT1082CN8 and LT1082CQ, the LT1082MJ8 offers hermetic ceramic packaging and 150°C junction rating-making it uniquely suitable for aerospace, downhole, or military applications demanding long-term reliability under thermal stress, despite higher cost and legacy status.
Availability
LT1082MJ8 is available at Aetrix Electronics and suitable for telecom power conversion, industrial isolated supplies, and high-voltage DC-DC modules requiring stable component supply, long-lifecycle support, and hermetic packaging integrity.
Supply support for LT1082MJ8 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
Linear Technology Corporation (now part of Analog Devices) is a U.S.-based semiconductor company specializing in high-performance analog ICs, including precision regulators, amplifiers, and power management solutions.
The LT1082 product line was designed for high-voltage, wide-input switching power supplies in telecom infrastructure, industrial automation, and instrumentation-emphasizing integration, isolation capability, and robust short-circuit protection.
FAQ
What is the maximum operating junction temperature for the LT1082MJ8?
The LT1082MJ8 has a maximum operating junction temperature (TJMAX) of 150°C, as specified for the J8 ceramic DIP package. This rating is confirmed in the Absolute Maximum Ratings table and supported by its θJA = 100°C/W thermal resistance. Operation beyond 150°C risks permanent damage; derating is required above 125°C ambient in typical layouts.
Does the LT1082MJ8 support isolated flyback regulation without an optocoupler?
Yes, the LT1082MJ8 supports isolated flyback regulation without an optocoupler via its dedicated flyback mode. When the FB pin draws 60–200µA, the internal flyback amplifier activates and regulates the amplitude of the reflected flyback pulse-directly controlling output voltage through transformer turns ratio. This eliminates optocouplers and secondary-side references.
What happens when the FB pin is pulled below 0.6V on the LT1082MJ8?
When the FB pin voltage drops to approximately 0.6V and the resulting sink current reaches ~350µA, the LT1082MJ8 initiates short-circuit frequency shift-down-reducing switching frequency from 60kHz to 12kHz. This prevents minimum-on-time violation during hard shorts at high input voltages (e.g., –70V telecom rails), maintaining regulation and preventing thermal runaway.
Can the LT1082MJ8 be synchronized to an external clock?
Yes, the LT1082MJ8 can be externally synchronized to a clock in the 75kHz to 90kHz range by pulling the VC pin to ground with a transistor. Pulse width must remain under 1µs to avoid disturbing error amplifier DC characteristics. Synchronization enables EMI reduction in multi-rail systems and avoids beat frequencies in dense power layouts.
What is the purpose of the NC pin (Pin 4) on the LT1082MJ8?
Pin 4 on the LT1082MJ8 is a no-connect (NC) terminal-internally unconnected and electrically isolated from all circuitry. It must remain unconnected on the PCB; routing traces or applying solder to this pin may cause unpredictable behavior or damage. This pin exists for mechanical compatibility with other package variants but carries no electrical function in the LT1082MJ8.
LT1082MJ8 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-CDIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive or Negative, Isolation Capable
- Topology:
- Buck, Boost, Flyback, Forward Converter
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 75V
- Voltage - Output (Min/Fixed):
- 1.244V
- Voltage - Output (Max):
- 100V (Switch)
- Current - Output:
- 850mA (Switch)
- Frequency - Switching:
- 12kHz ~ 60kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-CERDIP
LT1082MJ8 FAQ
1.How can I place an order for LT1082MJ8 through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1082MJ8 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 LT1082MJ8 reliable?
The price and inventory of LT1082MJ8 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1082MJ8 is usually 5 days.
3.What payment methods are accepted for LT1082MJ8?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1082MJ8 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1082MJ8?
LT1082MJ8 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1082MJ8 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 LT1082MJ8?
For technical support, including LT1082MJ8 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1082MJ8 requirements.
6.How does Aetrix verify that LT1082MJ8 is sourced from the original manufacturer or authorized distributors?
All LT1082MJ8 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 LT1082MJ8 meets industry standards.
7.What is the process for return or replacement of LT1082MJ8?
All LT1082MJ8 units undergo pre-shipment inspection (PSI). If there is an issue with LT1082MJ8, 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 LT1082MJ8 part is unused and in its original packaging.
Return procedure for LT1082MJ8:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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