Texas Instruments LM2586S-3.3

Overview

LM2586S-3.3 from Texas Instruments is a monolithic 3A flyback/boost/forward switching regulator IC with fixed 3.3V output, NPN 3.0A/65V switch, ±4% system output voltage tolerance, 4V–40V input range, and adjustable 100–200 kHz switching frequency. It operates in current-mode control for improved transient response and integrates soft-start, undervoltage lockout, thermal shutdown, and external shutdown capability - used in isolated DC-DC power supplies for industrial control and telecom interface modules.

For engineers reviewing the LM2586S-3.3 datasheet, LM2586S-3.3 pinout, LM2586S-3.3 application, or LM2586S-3.3 equivalent, key selection considerations include its TO-263-7 (S) package thermal performance (θJA = 26°C/W with 7.4× copper), 3.3V reference accuracy (3.242–3.358 V at TJ = −40°C to +125°C), flyback topology support with transformer-coupled multi-output designs, and compatibility with standard TI-recommended flyback transformers (e.g., Schott 67140890, Renco RL-5532).

Technical Context

The LM2586S-3.3 implements current-mode PWM control with an internal 3.0A NPN power switch rated for 65V off-state voltage and 0.45V typical saturation voltage at 3.0A. Its error amplifier features 1.193 mmho transconductance and 260 V/V open-loop gain, referenced to a trimmed 3.3V internal bandgap (not adjustable), enabling precise regulation across line/load/temperature.

Oscillator frequency is set via external resistor on Pin 1 (Freq Adj/ON-OFF), supporting synchronization to external clocks up to 200 kHz; short-circuit protection triggers at 25 kHz, and soft-start limits in-rush current using a 11.0 μA internal current source charging the compensation capacitor.

Key Specifications

Pinout & Package

LM2586S-3.3 uses a 7-lead TO-263 (S) surface-mount package with exposed thermal pad (pin 7 connected to GND). The package provides low thermal resistance (θJA = 26°C/W) when mounted on ≥1.0064 in² of 1 oz. copper.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar flyback/boost regulator applications.

Compared with LM2586S-3.3, LM2587S-3.3 offers integrated bootstrap diode for simpler boost layouts but reduced flyback flexibility, while UCC38C43D provides topology freedom and higher power scalability at the cost of added external components and design effort.

Availability

LM2586S-3.3 is available at Aetrix Electronics and suitable for industrial PLC power supplies, telecom line interface cards, automotive body control modules, and medical sensor interfaces requiring stable component supply and long-term production continuity.

Supply support for LM2586S-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 is a global semiconductor leader specializing in analog, embedded processing, and power management ICs, with decades of expertise in switching regulator design and manufacturing.

The LM2586S-3.3 belongs to TI's SIMPLE SWITCHER® family - engineered for ease-of-use in isolated and non-isolated DC-DC conversion, targeting cost-sensitive, high-reliability applications where minimal external components and proven transformer compatibility are critical.

FAQ

What is the maximum output current supported by the LM2586S-3.3 in flyback configuration?

The LM2586S-3.3 supports up to 1.2A output current in flyback configuration under specified conditions (VIN = 4–12V, TJ ≤ 125°C), as guaranteed by system-level testing in the datasheet. Internal current limiting protects the 3.0A NPN switch, but output current is externally constrained by transformer design, diode rating, and thermal management - exceeding 1.2A requires careful derating and heatsinking per TI Application Note SLVA001.

Does the LM2586S-3.3 require external feedback resistors to set the output voltage?

No, the LM2586S-3.3 does not require external feedback resistors. It integrates a factory-trimmed 3.3V reference directly connected to the FB pin, enabling fixed 3.3V regulation without any external divider network - this reduces component count, improves accuracy, and eliminates resistor tolerance drift effects on output voltage.

Can the LM2586S-3.3 be synchronized to an external clock signal?

Yes, the LM2586S-3.3 supports frequency synchronization via its Sync pin (Pin 1 when configured as Freq Adj/ON-OFF). Applying a TTL-compatible square wave (0.75V threshold, 100 μA input current) synchronizes the internal oscillator to the external clock, enabling noise reduction in multi-rail systems and EMI compliance in dense PCB layouts.

What is the recommended minimum copper area for the thermal pad of the LM2586S-3.3 in TO-263-7 package?

The LM2586S-3.3 datasheet specifies θJA = 26°C/W when mounted on 1.0064 in² (7.4× package footprint) of 1 oz. copper. For reliable 3A operation at ambient temperatures up to 75°C, TI recommends at minimum 0.4896 in² (3.6×) copper area; smaller areas increase junction temperature and require derating - always verify with thermal simulation or IR imaging during prototype validation.

How does the LM2586S-3.3 handle undervoltage lockout and thermal protection?

The LM2586S-3.3 incorporates undervoltage lockout (UVLO) that disables the switch when VIN drops below 3.05V (typical), preventing erratic operation during brownout. Thermal shutdown activates at TJ ≥ 150°C, halting switching until junction temperature falls below ~135°C hysteresis. Both protections are fully integrated - no external components required - and operate independently of the ON/OFF pin state.