Texas Instruments LM2597N-3.3

Overview

LM2597N-3.3 from Texas Instruments is a monolithic 150-kHz nonsynchronous step-down (buck) DC-DC converter delivering up to 0.5 A at a fixed 3.3-V output, with ±4% output voltage tolerance over line and load, 4.5–40-V input range, and integrated soft-start/shutdown control - used in embedded power supplies requiring compact, low-component-count 3.3-V regulation.

For engineers reviewing the LM2597N-3.3 datasheet, LM2597N-3.3 pinout, LM2597N-3.3 application, or LM2597N-3.3 equivalent, key selection criteria include its fixed 3.3-V output, 8-pin PDIP package, 150-kHz switching frequency, bias supply (VBS) capability for efficiency optimization, and error flag with delay for system reset sequencing.

Technical Context

The LM2597N-3.3 implements a current-mode controlled buck topology with an internal 150-kHz fixed-frequency oscillator, enabling stable operation with standard off-the-shelf inductors and minimal external components. Its architecture integrates a 0.5-A N-channel DMOS switch, internal frequency compensation, and thermal shutdown with two-stage current limiting.

It features dedicated pins for shutdown/soft-start (logic-level control with capacitor-programmable ramp), open-collector error flag with built-in 5% dropout detection and capacitor-delayed assertion, and a bias supply (VBS) input that powers internal circuitry from VOUT - improving efficiency at high VIN/low VOUT conditions, though not usable for the 3.3-V version due to VBS minimum voltage requirement (>4 V).

Key Specifications

Pinout & Package

LM2597N-3.3 is supplied in an 8-pin plastic dual in-line package (PDIP) with body size 9.81 mm × 6.35 mm, designed for through-hole mounting and prototyping-friendly layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Compared with LM2597MX-3.3, the LM2597N-3.3 offers identical regulation performance but enables hand-soldering and thermal testing via PDIP; versus LM2596-3.3, it trades higher current capability for superior soft-start control, error flag timing, and fault visibility - critical in safety-monitored systems.

Availability

LM2597N-3.3 is available at Aetrix Electronics and suitable for industrial sensor nodes, embedded microcontroller power supplies, legacy equipment retrofits, and positive-to-negative converter designs requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for LM2597N-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 technologies, with decades of expertise in highly reliable, application-optimized power conversion ICs.

The LM2597 series was designed specifically for cost-sensitive, medium-power DC-DC buck conversion in industrial, telecom, and embedded systems - emphasizing simplicity, minimal external parts, and robust fault protection without sacrificing accuracy or efficiency.

FAQ

What is the maximum input voltage rating for LM2597N-3.3?

The LM2597N-3.3 has a maximum input voltage rating of 40 V, as specified in the Absolute Maximum Ratings table. Operation above this level risks permanent damage. The related LM2597HV variant supports up to 60 V input, but LM2597N-3.3 is strictly rated for ≤40 V. Always maintain ≥10% derating margin in high-transient environments.

Can the LM2597N-3.3 be used in an inverting (positive-to-negative) configuration?

Yes, the LM2597N-3.3 can be configured as a positive-to-negative converter by bootstrapping the ground pin to the negative output and grounding the feedback pin - per Figure 24 in the datasheet. This produces a regulated –3.3-V rail from a positive input. Note that startup current may reach 0.8 A briefly, so soft-start is strongly recommended.

Does the LM2597N-3.3 require external feedback resistors?

No, the LM2597N-3.3 does not require external feedback resistors. It is a fixed-output variant with internal 3.3-V reference and feedback network - pin 4 (Feedback) connects directly to the internal reference node. External resistors are only needed for the adjustable version (LM2597ADJ).

What is the purpose of the Bias Supply (VBS) pin on LM2597N-3.3?

The VBS pin on LM2597N-3.3 is intended to power internal circuitry from the output rail instead of VIN - improving efficiency at high input voltages. However, because the LM2597N-3.3 outputs only 3.3 V and VBS requires ≥4 V to operate, this pin must be left open (unconnected) for this specific part. It remains functional only in 5-V, 12-V, or adjustable versions.

How does the error flag and delay functionality work on LM2597N-3.3?

The LM2597N-3.3 asserts its open-collector Error Flag pin low when VOUT falls below 95% of 3.3 V. At power-up, the flag stays low until VOUT reaches that threshold and a user-defined delay (set by capacitor on pin 2) expires. This provides a clean, glitch-free power-good signal for microcontroller reset or system enable sequencing.