Texas Instruments LM2825N-3.3/NOPB

Overview

LM2825N-3.3/NOPB from Texas Instruments is a self-contained 1A step-down (buck) DC-DC converter in a 24-pin PDIP package, delivering a fixed 3.3V output with ±4% tolerance, operating from 4.75V to 40V input, and achieving up to 75% efficiency at 12V_IN/0.5A_LOAD. It integrates all active and passive components for high-efficiency regulation in industrial power supplies and embedded systems requiring stable low-voltage rails.

For engineers reviewing the LM2825N-3.3/NOPB datasheet, LM2825N-3.3/NOPB pinout, LM2825N-3.3/NOPB application, or LM2825N-3.3/NOPB equivalent, key selection considerations include its no-external-components requirement for fixed-output operation, 65 μA standby current, thermal shutdown protection, TTL-compatible shutdown control, and compliance with CISPR 22 Class B radiated EMI limits.

Technical Context

The LM2825N-3.3/NOPB implements a monolithic buck regulator architecture with internal MOSFET switch, PWM controller, oscillator (150 kHz), feedback error amplifier, and thermal/current-limit protection circuitry. Its fixed 3.3V output eliminates external resistor dividers, and the SD/SS pin enables TTL-level shutdown and programmable soft-start via external capacitor.

It operates across −40°C to +85°C ambient temperature, supports input-to-output differential ≥2V for proper regulation, and delivers up to 1A load current-derated per input/output voltage and junction temperature per TI's published curves. Output ripple is specified at 40 mV_p-p under 12V_IN/1A conditions.

Key Specifications

Pinout & Package

The LM2825N-3.3/NOPB uses a 24-pin plastic dual-in-line package (PDIP), package drawing NFL, measuring 1.25 × 0.54 × 0.26 inches (31.8 × 13.7 × 6.6 mm), with through-hole mounting and copper lead frame for thermal conduction to PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2825N-3.3/NOPB, LM2678-3.3/NOPB offers higher current headroom at the cost of external component count, while TPS5430DDAR delivers superior efficiency and integration but shifts EMI and stability responsibility to the designer - making LM2825N-3.3/NOPB optimal for rapid, low-risk 1A fixed-output deployments.

Availability

LM2825N-3.3/NOPB is available at Aetrix Electronics and suitable for industrial power supplies, embedded control systems, test equipment, and distributed power architectures requiring stable component supply, long-lifecycle support, and RoHS-compliant through-hole packaging.

Supply support for LM2825N-3.3/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 technologies, with decades of expertise in high-reliability power conversion ICs.

The LM2825 product line was designed to deliver fully integrated, easy-to-use DC-DC buck solutions for industrial, instrumentation, and telecom applications where rapid design-in, robust protection, and EMI compliance are critical.

FAQ

What is the minimum input voltage required for stable operation of the LM2825N-3.3/NOPB?

The LM2825N-3.3/NOPB requires a minimum input voltage of 4.75V to maintain regulation at its nominal 3.3V output. Below this threshold, the device enters dropout and output voltage drops linearly with input. This 4.75V limit ensures sufficient headroom for the internal switch and control circuitry to operate reliably across temperature and load variations, as confirmed in TI's Operating Ratings table.

Does the LM2825N-3.3/NOPB require external components to function?

Yes, the LM2825N-3.3/NOPB requires external input and output capacitors for stable operation, though it needs no external resistors, inductors, or diodes for basic functionality. TI's standard test circuit (Figure 17) specifies a 100 μF input capacitor and 220 μF output capacitor; optional soft-start and feed-forward capacitors may be added for enhanced transient response or reduced ripple, but are not mandatory for nominal operation.

How does the shutdown feature of the LM2825N-3.3/NOPB work?

The LM2825N-3.3/NOPB uses its SD/SS pin for dual-function control: applying ≤0.6V places the device in shutdown mode with 65 μA quiescent current, while applying ≥2.0V initiates soft-start mode with controlled output voltage ramp-up. The pin is TTL-compatible and draws only 5 μA in shutdown, enabling direct interfacing with microcontroller GPIOs without level-shifting or buffering circuitry.

What is the maximum allowable output current for the LM2825N-3.3/NOPB at 85°C ambient temperature?

At 85°C ambient temperature, the LM2825N-3.3/NOPB's maximum continuous output current is derated to approximately 0.75A, as shown in TI's Figure 23 (Output Current Derating for TA = 70°C to 85°C). This limitation results from thermal constraints - junction temperature must remain ≤125°C - and applies regardless of input voltage, requiring adequate PCB copper area or forced airflow for full 1A operation at elevated temperatures.

Is the LM2825N-3.3/NOPB compliant with RoHS and lead-free soldering standards?

Yes, the LM2825N-3.3/NOPB is RoHS-compliant and qualified for lead-free soldering. Its "/NOPB" suffix indicates Green (RoHS & no Sb/Br) construction with Cu-Sn lead finish, moisture sensitivity level (MSL) rating of Level-1 (unlimited floor life), and compatibility with standard reflow profiles per JEDEC J-STD-020. TI confirms this part meets all substance restrictions under EU Directive 2011/65/EU.