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Texas Instruments LM2577T-ADJ/LB02
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- Part No.:
- LM2577T-ADJ/LB02
- Manufacturer:
- Texas Instruments
- Package:
- TO-220-5 Formed Leads
- Datasheet:
-
LM2577T-ADJ/LB02.pdf
- Description:
- IC REG BST FLYBCK ADJ 3A TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:2,135
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Product details
Overview
LM2577T-ADJ/LB02 from Texas Instruments is a monolithic step-up (boost) switching voltage regulator IC featuring an integrated 3.0A NPN power switch, 52 kHz fixed-frequency oscillator, current-mode control, and adjustable output via external resistor divider. It operates from 3.5V to 40V input and delivers up to 60V output with internal current limit, thermal shutdown, and undervoltage lockout - used in industrial power supplies and battery-powered boost converters.
For engineers reviewing the LM2577T-ADJ/LB02 datasheet, LM2577T-ADJ/LB02 pinout, LM2577T-ADJ/LB02 application, or LM2577T-ADJ/LB02 equivalent, key selection criteria include its TO-220 (T) package, 1.230 V reference voltage, 3.0 A switch current rating, soft-start function, and compatibility with standard flyback transformers and off-the-shelf inductors per TI's recommended designs.
Technical Context
The LM2577T-ADJ/LB02 implements current-mode PWM control using an internal error amplifier comparing feedback voltage against a precise 1.230 V reference, modulating switch duty cycle to regulate output. Its 52 kHz oscillator sets switching frequency independent of external components, enabling predictable EMI behavior and simplified filter design.
It integrates protection functions including undervoltage lockout (2.70–3.15 V threshold), thermal shutdown, and current limiting - with switch current internally limited to 3.0 A under normal operation but requiring external peak-current limiting in boost topology per TI Application Hints. The device supports adjustable output via two external resistors connected to the feedback pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Topology | Step-up (boost), flyback, forward - enables single-stage DC-DC conversion above input voltage. |
| Reference Voltage | 1.230 V ±16 mV - sets output regulation point via external R1/R2 divider; determines accuracy of adjustable output. |
| Switch Current | 3.0 A continuous - defines maximum inductor peak current capability; requires external current limiting in boost configuration. |
| Oscillator Frequency | 52 kHz ±10% - fixed internal timing enables stable loop response and predictable LC filter sizing. |
| Input Voltage Range | 3.5 V to 40 V - supports wide-range inputs including 5 V, 12 V, and 24 V rails and battery-derived supplies. |
| UVLO Threshold | 2.70 V to 3.15 V - prevents erratic startup during brownout; ensures reliable turn-on only when supply is sufficient. |
| Max Output Voltage | 60 V - constrains safe operating area for diode and capacitor selection in high-voltage boost designs. |
Pinout & Package
LM2577T-ADJ/LB02 uses a 5-lead TO-220 (T) package (NS Package Number T05A), with the tab electrically connected to Pin 2 (Ground). Thermal performance relies on PCB copper area attached to the tab.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Input) | Power Input | Connects to unregulated DC input (3.5–40 V); must be decoupled near device with low-ESR capacitor. |
| 2 (Ground) | Power & Signal Ground | Common return for input, output, feedback, and compensation; tied to metal tab for thermal conduction. |
| 3 (Feedback) | Regulation Sense | Monitors output via resistor divider; compares to 1.230 V reference to adjust duty cycle for stable output. |
| 4 (Output Switch) | NPN Collector | Drives external inductor/diode; switches at 52 kHz; withstands up to 65 V when off. |
| 5 (Compensation) | Error Amplifier Output | Provides loop compensation node; connects to RC network for stability tuning in adjustable configurations. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 3.0 A NPN switch | Reduces BOM count by eliminating external transistor; simplifies layout but requires careful thermal management in TO-220. |
| Current-mode control | Improves transient response and line/load regulation; enables inherent cycle-by-cycle current limiting without extra sensing circuitry. |
| Soft-start function | Gradually ramps output during startup to limit in-rush current into output capacitors - critical for reliability in high-COUT designs. |
| Fixed 52 kHz oscillator | Eliminates need for external timing components; ensures consistent switching frequency across temperature and supply variations. |
| Undervoltage lockout | Prevents operation below 2.70 V, avoiding unstable regulation or latch-up during power-up/down sequences. |
Applications
| Industrial Power Supply | Portable Instrumentation |
|---|---|
|
Use Scenario: Generating 24 V from a 9 V battery-powered test instrument with variable load demand. IC Role / Device Role / Timing Role: Step-up regulator providing regulated 24 V output; controls energy transfer via 52 kHz PWM and current-mode feedback. Use Value: Enables compact, efficient high-voltage rail without transformer-based isolation - reducing size and cost over linear solutions. |
Use Scenario: Boosting 3.7 V Li-ion battery voltage to 5 V for microcontroller and sensor subsystems in handheld meters. IC Role / Device Role / Timing Role: Adjustable-output DC-DC converter regulating 5 V output via external resistor divider; manages battery discharge curve. Use Value: Extends usable battery life by maintaining stable 5 V until battery drops below 3.5 V - leveraging wide VIN range and soft-start. |
| Automotive Aftermarket | LED Driver Interface |
|
Use Scenario: Converting 12 V vehicle bus to 24 V for legacy sensors or actuators in retrofit installations. IC Role / Device Role / Timing Role: Non-isolated boost converter with UVLO protection; handles cold-crank transients down to 3.5 V. Use Value: Provides robust, automotive-grade voltage translation without complex supervision circuitry - validated for −40°C to +125°C junction operation. |
Use Scenario: Driving constant-current LED strings from 5 V logic rails in signage or indicator panels. IC Role / Device Role / Timing Role: Boost controller supplying regulated voltage to external LED driver IC; sets headroom via adjustable output. Use Value: Allows flexible LED string configuration (e.g., 3–5 LEDs) by tuning output voltage precisely - minimizing power loss in series current regulation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-up regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2577T-12 | Fixed 12 V output; no external feedback resistors required; identical pinout and thermal specs. | Suitable where fixed 12 V output suffices; eliminates R1/R2 design effort but lacks output flexibility. | Select LM2577T-12 if system requires only 12 V and benefits from reduced component count and layout simplicity. |
| LM2577S-ADJ | Same electrical specs but in TO-263 (S) surface-mount package; θJA = 37°C/W with 1 in² copper vs. 65°C/W for TO-220. | Better thermal performance in space-constrained PCBs; requires rework for through-hole replacement. | Choose LM2577S-ADJ for automated SMT assembly or higher-power density designs needing improved thermal resistance. |
Compared with LM2577T-12 and LM2577S-ADJ, the LM2577T-ADJ/LB02 uniquely balances adjustable output capability with through-hole manufacturability and proven thermal behavior in TO-220 - making it optimal for prototyping, industrial field-service units, and medium-volume production where manual assembly or heatsink mounting is preferred.
Availability
LM2577T-ADJ/LB02 is available at Aetrix Electronics and suitable for industrial power supplies, portable instrumentation, automotive aftermarket modules, and LED driver interfaces requiring stable component supply and long-term obsolescence management.
Supply support for LM2577T-ADJ/LB02 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
Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in power management ICs and broad industrial application support.
The LM2577 product line was designed for cost-sensitive, medium-power DC-DC conversion in non-isolated boost, flyback, and forward topologies - targeting applications where simplicity, reliability, and minimal external components are critical.
FAQ
What is the reference voltage of the LM2577T-ADJ/LB02 and how does it affect output adjustment?
The LM2577T-ADJ/LB02 features a precision 1.230 V reference voltage at the feedback pin. This voltage serves as the regulation setpoint: output voltage is determined by the resistor divider ratio (R1/R2) between output and ground, where VOUT = 1.230 × (1 + R1/R2). Tight tolerance (±16 mV) ensures accurate output setting across temperature and load, critical for stable adjustable rail generation in the LM2577T-ADJ/LB02.
Does the LM2577T-ADJ/LB02 require external current limiting in boost configuration?
Yes - per TI Application Hints, the LM2577T-ADJ/LB02's internal current limit cannot fully protect the switch in boost topology due to timing constraints. External peak-current limiting (e.g., via inductor saturation or sense-resistor feedback) is required to prevent damage when peak switch current exceeds 3.0 A. This is a documented design requirement specific to the LM2577T-ADJ/LB02 in step-up mode, not a general limitation.
What is the thermal resistance (θJA) of the LM2577T-ADJ/LB02 in its TO-220 package?
The LM2577T-ADJ/LB02 in the 5-lead TO-220 (T) package has a junction-to-ambient thermal resistance (θJA) of 65°C/W under standard JEDEC conditions (1 in² copper pad). With enhanced PCB copper area thermally connected to the tab, θJA can be reduced - but the baseline 65°C/W value must be used for worst-case thermal design of the LM2577T-ADJ/LB02 in typical through-hole mounting.
Can the LM2577T-ADJ/LB02 be used in flyback or forward converter topologies?
Yes - the LM2577T-ADJ/LB02 is explicitly specified for flyback and forward converter applications in its datasheet. In those topologies, internal current limiting is fully functional and provides protection without external intervention. Its error amplifier, 52 kHz oscillator, and 3.0 A NPN switch are architected to support all three modes - making the LM2577T-ADJ/LB02 versatile across isolated and non-isolated designs.
What is the purpose of the Compensation (Pin 5) on the LM2577T-ADJ/LB02?
Pin 5 (Compensation) is the output of the internal error amplifier and serves as the loop compensation node. It connects to an external RC network to stabilize the control loop - adjusting phase margin and transient response. Proper compensation is essential for reliable regulation in adjustable-output configurations of the LM2577T-ADJ/LB02, especially with varying output capacitance or load dynamics.
LM2577T-ADJ/LB02 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- TO-220-5 Formed Leads
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Boost, Flyback, Forward Converter
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.5V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.23V
- Voltage - Output (Max):
- 60V (Switch)
- Current - Output:
- 3A (Switch)
- Frequency - Switching:
- 52kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220-5
LM2577T-ADJ/LB02 FAQ
1.How can I place an order for LM2577T-ADJ/LB02 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2577T-ADJ/LB02 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 LM2577T-ADJ/LB02 reliable?
The price and inventory of LM2577T-ADJ/LB02 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2577T-ADJ/LB02 is usually 5 days.
3.What payment methods are accepted for LM2577T-ADJ/LB02?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2577T-ADJ/LB02 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2577T-ADJ/LB02?
LM2577T-ADJ/LB02 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2577T-ADJ/LB02 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 LM2577T-ADJ/LB02?
For technical support, including LM2577T-ADJ/LB02 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2577T-ADJ/LB02 requirements.
6.How does Aetrix verify that LM2577T-ADJ/LB02 is sourced from the original manufacturer or authorized distributors?
All LM2577T-ADJ/LB02 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 LM2577T-ADJ/LB02 meets industry standards.
7.What is the process for return or replacement of LM2577T-ADJ/LB02?
All LM2577T-ADJ/LB02 units undergo pre-shipment inspection (PSI). If there is an issue with LM2577T-ADJ/LB02, 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 LM2577T-ADJ/LB02 part is unused and in its original packaging.
Return procedure for LM2577T-ADJ/LB02:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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