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Texas Instruments LM2585T-3.3
- Part No.:
- LM2585T-3.3
- Manufacturer:
- Texas Instruments
- Package:
- TO-220-5 Formed Leads
- Datasheet:
-
LM2585T-3.3.pdf
- Description:
- IC REG BST FLYBACK 3.3V TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:3,836
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Product details
Overview
LM2585T-3.3 from Texas Instruments (formerly National Semiconductor) is a monolithic 3A flyback/boost regulator IC with fixed 3.3V output, 100 kHz fixed-frequency oscillator, 4V–40V input range, and integrated 65V NPN power switch. It delivers ±4% output voltage tolerance over line and load, supports flyback, boost, and forward converter topologies, and is used in industrial power supplies requiring isolated or stepped-up DC outputs.
For engineers reviewing the LM2585T-3.3 datasheet, LM2585T-3.3 pinout, LM2585T-3.3 application, or LM2585T-3.3 equivalent, key selection criteria include its 3.3V fixed output, TO-220-5 package thermal performance (θJA = 65°C/W, no heatsink), current-mode control for transient response, soft-start function, and compatibility with standard flyback transformers like Coilcraft T7.
Technical Context
The LM2585T-3.3 implements current-mode PWM control with an internal 100 kHz oscillator, enabling stable regulation using small magnetics. Its error amplifier features transconductance of 1.193 mmho and voltage gain of 260 V/V, referenced to a 3.3V internal feedback node (VREF = 3.3V, ±1.8% over temperature).
Protection includes cycle-by-cycle current limiting, undervoltage lockout (VUV = 3.30V), thermal shutdown, and switch voltage clamping up to 65V. The device operates across −40°C to +125°C junction temperature and requires external components for flyback transformer biasing, output rectification, and compensation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±4% over full line/load/temperature range - ensures stable logic supply without external feedback resistors. |
| Input Voltage Range | 4V to 40V - supports wide-input industrial and automotive battery-derived rails. |
| Switch Current Limit | 3.0A peak - defines maximum primary-side energy transfer in flyback mode; requires external current limiting in boost configuration. |
| Oscillator Frequency | 100 kHz (±15%) - enables use of compact, low-cost off-the-shelf magnetics (e.g., Coilcraft T7, Renco RL-5751). |
| Thermal Resistance | θJA = 65°C/W (TO-220, no heatsink) - limits continuous output power to ~3.5W at 25°C ambient without forced cooling. |
| Output Tolerance | ±4% system-level - guaranteed across 0.3A–1.2A load and 4V–12V input per test circuit Figure 2. |
| Soft-Start Current | 11.0 μA - controls ramp rate of output voltage during startup to limit inrush into downstream capacitance. |
Pinout & Package
LM2585T-3.3 is housed in a 5-lead TO-220 package (NSC drawing T05D) with bent, staggered leads. The exposed tab is electrically connected to Pin 2 (Ground) and serves as the primary thermal path.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1: Input | Power input | Accepts 4V–40V unregulated DC; connects to bulk input capacitor (≥100 μF). |
| Pin 2: Ground | Reference node | Common return for input, output, and feedback paths; tab connection enables heatsinking. |
| Pin 3: Feedback | Voltage sense | Monitors regulated output via resistor divider; internally referenced to 3.3V for fixed version. |
| Pin 4: Switch | NPN collector | Drives primary winding of flyback transformer or boost inductor; switches at 100 kHz. |
| Pin 5: Compensation | Error amp output | Provides access to internal error amplifier output for loop stability tuning with RC network. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 3A/65V NPN switch | Eliminates need for external high-voltage transistor; reduces BOM count and layout complexity in isolated converters. |
| Current-mode control | Enables inherent line/load transient rejection and simplifies loop compensation vs. voltage-mode designs. |
| Internal soft-start | Reduces peak inrush current during startup-critical for reliability when charging large output capacitors. |
| Undervoltage lockout (UVLO) | Prevents erratic operation below 3.05V input, ensuring clean start-up only within valid operating range. |
| ±4% output tolerance | Guaranteed system-level accuracy eliminates need for post-regulation trimming in cost-sensitive applications. |
Applications
| Industrial Flyback Power Supply | Automotive Boost Converter |
|---|---|
Use Scenario: Isolated 3.3V rail generation from 12V vehicle battery for microcontroller and sensor subsystems. IC Role / Device Role / Timing Role: Primary-side controller implementing flyback topology with transformer isolation and 100 kHz switching. Use Value: Enables single-chip isolated DC/DC conversion with built-in protection, eliminating need for external gate driver or controller IC. | Use Scenario: Stepping up 5V USB-C PD source to 12V for legacy peripherals in portable test equipment. IC Role / Device Role / Timing Role: Fixed-output boost regulator operating at 100 kHz to minimize EMI and inductor size. Use Value: Delivers 3A peak switch current capability with internal current limiting, reducing risk of inductor saturation under transient loads. |
| Medical Sensor Interface PSU | Telecom Line Card Bias Supply |
Use Scenario: Generating isolated 3.3V and −12V dual outputs from 24V backplane in patient-monitoring front-end modules. IC Role / Device Role / Timing Role: Flyback controller driving center-tapped transformer for multiple secondary windings. Use Value: Supports multi-output configurations with tight cross-regulation via shared magnetic coupling and fixed 3.3V reference accuracy. | Use Scenario: Providing 3.3V bias for analog front-end ICs in telecom line cards powered from −48V DC distribution. IC Role / Device Role / Timing Role: Boost regulator converting negative −48V to positive 3.3V using inverting topology with external PNP stage. Use Value: Leverages wide 4V–40V input range to accommodate degraded −48V rails down to −36V while maintaining regulated output. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar flyback/boost regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2585S-3.3 | Same silicon die, but in TO-263-5 (S) package with θJA = 35°C/W (7.4× copper area) - superior thermal performance. | Preferred for higher-power or convection-cooled designs where PCB real estate allows surface-mount footprint. | Select LM2585S-3.3 when thermal headroom is constrained and TO-263 mounting is feasible. |
| LM2577-3.3 | Lower 2.5A switch rating, 50 kHz frequency, different pinout (no COMP pin), and ±2% output tolerance - not pin-compatible. | Suitable for lower-current (<1A) non-isolated boost applications where smaller magnetics are acceptable. | Choose LM2577-3.3 only for cost-optimized, low-power boost designs where flyback isolation is unnecessary. |
Compared with LM2585S-3.3, the LM2585T-3.3 trades thermal efficiency for through-hole mechanical robustness and ease of prototyping; versus LM2577-3.3, it offers higher current, isolation capability, and dedicated compensation control-making it uniquely suited for industrial flyback systems demanding reliability and design flexibility.
Availability
LM2585T-3.3 is available at Aetrix Electronics and suitable for industrial power supplies, medical sensor interfaces, and telecom line card biasing requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM2585T-3.3 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 acquired National Semiconductor in 2011 and maintains full technical and manufacturing continuity for the SIMPLE SWITCHER® product line.
The LM2585 series was designed specifically for cost-sensitive, medium-power isolated and non-isolated DC/DC conversion in industrial, automotive, and telecom infrastructure-emphasizing minimal external component count and robust protection.
FAQ
What is the maximum continuous output current achievable with LM2585T-3.3 in a flyback configuration?
The LM2585T-3.3 supports up to 1.2A continuous output current in flyback mode per datasheet Figure 2 test conditions (VIN = 4V–12V). This assumes proper transformer selection (e.g., Coilcraft T7), adequate PCB copper area for thermal dissipation, and operation within −40°C to +125°C junction temperature limits. At higher ambient temperatures or with insufficient heatsinking, derating is required due to its 65°C/W θJA.
Does LM2585T-3.3 require external feedback resistors to set the output voltage?
No. The LM2585T-3.3 integrates a precision 3.3V reference and fixed feedback network. Pin 3 (Feedback) connects directly to the output in standard flyback or boost configurations-no external resistors are needed. This distinguishes it from the adjustable LM2585-ADJ variant, which requires R1/R2 to program VOUT.
Can LM2585T-3.3 be used in a non-isolated boost topology?
Yes. The LM2585T-3.3 is explicitly validated for boost operation per datasheet Figure 30 and typical applications. It delivers regulated 3.3V output from inputs as low as 4V. However, output current must be externally limited to ≤3A since the internal current limit does not protect the entire boost path during short-circuit events.
What is the purpose of the Compensation (COMP) pin on LM2585T-3.3?
The COMP pin provides direct access to the error amplifier output, enabling external loop compensation with an RC network. This allows designers to optimize phase margin and transient response for specific transformer, diode, and capacitor combinations-critical for stable regulation across varying loads and input voltages in both flyback and boost configurations.
Is LM2585T-3.3 RoHS compliant and lead-free?
Yes. LM2585T-3.3 is manufactured in RoHS-compliant, lead-free TO-220 packages per Texas Instruments' product change notices. The device meets JEDEC J-STD-020 moisture sensitivity level (MSL) 3 and is rated for reflow soldering up to 260°C for 10 seconds, consistent with industry-standard lead-free assembly processes.
LM2585T-3.3 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:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 3A (Switch)
- Frequency - Switching:
- 100kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220-5
LM2585T-3.3 FAQ
1.How can I place an order for LM2585T-3.3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2585T-3.3 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 LM2585T-3.3 reliable?
The price and inventory of LM2585T-3.3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2585T-3.3 is usually 5 days.
3.What payment methods are accepted for LM2585T-3.3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2585T-3.3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2585T-3.3?
LM2585T-3.3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2585T-3.3 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 LM2585T-3.3?
For technical support, including LM2585T-3.3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2585T-3.3 requirements.
6.How does Aetrix verify that LM2585T-3.3 is sourced from the original manufacturer or authorized distributors?
All LM2585T-3.3 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 LM2585T-3.3 meets industry standards.
7.What is the process for return or replacement of LM2585T-3.3?
All LM2585T-3.3 units undergo pre-shipment inspection (PSI). If there is an issue with LM2585T-3.3, 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 LM2585T-3.3 part is unused and in its original packaging.
Return procedure for LM2585T-3.3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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