Texas Instruments LM2577N-12/NOPB

Overview

LM2577N-12/NOPB from Texas Instruments is a monolithic step-up (boost) switching voltage regulator with fixed 12 V output, integrated 3.0 A NPN power switch, 52 kHz oscillator, and current-mode control architecture. It operates from 3.5 V to 40 V input, delivers up to 800 mA load current, and includes undervoltage lockout, thermal shutdown, and current limiting-used in industrial power supplies and battery-powered instrumentation requiring compact, low-component-count DC-DC conversion.

For engineers reviewing the LM2577N-12/NOPB datasheet, LM2577N-12/NOPB pinout, LM2577N-12/NOPB application, or LM2577N-12/NOPB equivalent, key selection criteria include its fixed 12 V output accuracy (±3.3% over temperature), TO-220-16 DIP package thermal resistance (θ_JA = 85°C/W), soft-start function for in-rush current control, and compatibility with standard off-the-shelf flyback inductors per TI's reference design guidelines.

Technical Context

The LM2577N-12/NOPB implements current-mode control using an internal error amplifier with 370 μmho transconductance and 80 V/V open-loop gain, comparing feedback voltage against a 12 V internal reference to modulate switch duty cycle. Its 52 kHz fixed-frequency oscillator drives the NPN output switch directly without external timing components.

Protection logic integrates undervoltage lockout (2.7–3.15 V threshold), thermal shutdown at 150°C junction temperature, and current limiting that restricts peak switch current to 3.7–6.0 A depending on operating conditions-enabling robust operation in unregulated input environments such as automotive or wide-range DC bus applications.

Key Specifications

Pinout & Package

LM2577N-12/NOPB uses a 16-pin dual-inline-package (DIP) with NS package number N16A. The package has no internal connection on pins 1, 2, 15, and 16 - these are NC (no-connect) terminals used for mechanical stability and thermal relief.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2577T-12/NOPB, the LM2577N-12/NOPB trades thermal performance for through-hole DIP compatibility and legacy board reuse; versus MC34063AP1G, it offers plug-and-play 12 V regulation with superior protection integration but less configurability.

Availability

LM2577N-12/NOPB is available at Aetrix Electronics and suitable for industrial power supplies, portable test equipment, automotive aftermarket modules, and legacy industrial control interfaces requiring stable component supply and long-lifecycle support.

Supply support for LM2577N-12/NOPB 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 LM2577 family was engineered for cost-sensitive, medium-power DC-DC conversion in industrial, automotive, and instrumentation systems-emphasizing simplicity, reliability, and minimal external component count.

FAQ

What is the maximum output current capability of the LM2577N-12/NOPB?

The LM2577N-12/NOPB supports up to 800 mA continuous output current under typical conditions (5 V input, 25°C ambient, adequate PCB copper). Peak switch current is internally limited to 3.7–6.0 A, but practical output current depends on input voltage, thermal management, and inductor saturation rating-designs should verify peak inductor current stays below 3.0 A to avoid switch overstress. The LM2577N-12/NOPB datasheet specifies 800 mA as the maximum tested load for guaranteed 12 V regulation.

Does the LM2577N-12/NOPB require external feedback resistors?

No, the LM2577N-12/NOPB has an internal 12 V feedback reference connected directly to the FB pin, eliminating the need for external resistors. Pin 5 (FB) is internally tied to the 12 V output, making it a true fixed-output device. This simplifies layout and improves accuracy versus adjustable regulators where resistor tolerance and drift affect regulation. The LM2577N-12/NOPB is designed for drop-in replacement in legacy 12 V boost applications without circuit modification.

What package type does the LM2577N-12/NOPB use, and how does it affect thermal performance?

The LM2577N-12/NOPB uses a 16-pin plastic DIP (dual-inline-package) with NS package code N16A. Its junction-to-ambient thermal resistance (θ_JA) is 85°C/W with standard PCB mounting-significantly higher than the TO-220 variant (65°C/W) due to reduced copper area and thermal mass. To maintain safe operation below 125°C junction temperature, designs must provide ≥1 in² of 2-oz copper pour connected to Pin 4 (GND) and ensure airflow or ambient temperature remains ≤50°C. The LM2577N-12/NOPB is optimized for legacy through-hole assembly, not high-power density.

Can the LM2577N-12/NOPB operate from a 3.3 V input source?

No-the LM2577N-12/NOPB has a minimum input voltage of 3.5 V per its Absolute Maximum Ratings and Operating Ratings tables. At 3.3 V, the internal undervoltage lockout (UVLO) circuit-active below 2.7–3.15 V-will prevent startup, but more critically, the device cannot sustain regulation to 12 V from 3.3 V due to duty-cycle limitations (V_OUT ≤ 10 × V_IN(min) per design constraints). For 3.3 V input, a different boost regulator such as the TPS61040 or MAX77801 is required. The LM2577N-12/NOPB is specified only for 3.5–40 V input operation.

How does the soft-start function work in the LM2577N-12/NOPB?

The LM2577N-12/NOPB implements soft-start by sourcing a controlled 2.5–9.5 μA current into the COMP pin during startup, gradually charging the external compensation capacitor and ramping the duty cycle from zero. This limits in-rush current into output capacitors, preventing input rail collapse and reducing stress on the internal NPN switch and external diode. The soft-start duration is set by the COMP capacitor value and is typically 1–5 ms-fully documented in the LM2577N-12/NOPB Application Hints section. No external enable signal is required; soft-start is automatic and integral to the LM2577N-12/NOPB architecture.