Texas Instruments LM2597M-ADJ/NOPB

Overview

LM2597M-ADJ/NOPB from Texas Instruments is a monolithic nonsynchronous step-down (buck) DC-DC switching regulator IC delivering up to 0.5 A output current with adjustable output voltage from 1.2 V to 37 V, fixed 150-kHz switching frequency, and input voltage range up to 40 V. It integrates internal frequency compensation, soft-start, shutdown control, and an error flag for power sequencing in industrial and embedded power supplies.

For engineers reviewing the LM2597M-ADJ/NOPB datasheet, LM2597M-ADJ/NOPB pinout, LM2597M-ADJ/NOPB application, or LM2597M-ADJ/NOPB equivalent, key selection criteria include output adjustability via feedback resistor divider, bias supply (VBS) pin for efficiency optimization at high VIN/low VOUT, ±4% output voltage tolerance over line/load/temperature, and thermal shutdown protection.

Technical Context

The LM2597M-ADJ/NOPB implements a current-mode controlled buck topology with a built-in N-channel DMOS switch, internal oscillator, and error amplifier. Its feedback pin senses voltage at the divider midpoint to regulate output, while the VBS pin enables powering internal circuitry from VOUT instead of VIN-reducing quiescent current and improving efficiency under light-load/high-input conditions.

It features dual-function Shutdown/Soft-Start pin enabling logic-level disable (ISTBY = 85 μA typical) and capacitor-controlled ramp-up, plus an open-collector Error_Flag output with programmable delay via external capacitor on the Delay pin-supporting microprocessor reset assertion after stable output is achieved.

Key Specifications

Pinout & Package

LM2597M-ADJ/NOPB is supplied in an 8-pin SOIC (D) package measuring 4.90 mm × 3.91 mm, optimized for surface-mount assembly and thermal performance (R_θJA = 95°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2596-ADJ, LM2597M-ADJ/NOPB delivers superior efficiency under high-input/low-output conditions via its VBS pin; versus LM2678-ADJ, it offers simpler implementation with internal compensation but lower current capability-making it optimal for compact, cost-sensitive 0.5-A buck designs.

Availability

LM2597M-ADJ/NOPB is available at Aetrix Electronics and suitable for industrial power supplies, embedded system pre-regulators, positive-to-negative converters, and automotive aftermarket modules requiring stable component supply and long-term manufacturability.

Supply support for LM2597M-ADJ/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 LM2597 series belongs to TI's SIMPLE SWITCHER® portfolio-designed specifically for ease-of-use in non-isolated DC-DC buck applications where minimal external components, internal compensation, and robust protection features are essential.

FAQ

What is the minimum input voltage required for LM2597M-ADJ/NOPB to regulate properly?

The LM2597M-ADJ/NOPB requires a minimum input voltage of 4.5 V to maintain regulation across its full output range. Below this threshold, the internal circuitry cannot sustain oscillation or drive the switch effectively. At VOUT = 1.2 V, VIN must exceed approximately 2.5 V plus diode and switch losses-but per datasheet specifications, 4.5 V is the guaranteed functional minimum under all operating conditions. Always verify startup behavior with actual external components in your design.

Can LM2597M-ADJ/NOPB be used in an inverting (positive-to-negative) configuration?

Yes, LM2597M-ADJ/NOPB supports inverting operation by floating the GND pin to the negative output and referencing the FB pin to system ground-enabling generation of regulated negative voltages such as −5 V or −12 V. The datasheet provides Figure 24 as a validated schematic, including required external diode D1 and soft-start integration. Maximum |VIN| + |VOUT| must remain ≤ 40 V to avoid exceeding absolute maximum ratings.

How does the Bias Supply (VBS) pin improve efficiency in LM2597M-ADJ/NOPB?

The VBS pin in LM2597M-ADJ/NOPB allows internal circuitry to be powered from VOUT instead of VIN-reducing total input current draw and lowering junction temperature. This yields measurable efficiency gains (e.g., +3–5% at VIN = 36 V, VOUT = 5 V, ILOAD = 0.1 A), particularly under light loads or high input-to-output ratios. The VBS pin requires ≥3.5 V and functions up to 30 V, but benefits plateau above ~15 V.

What is the purpose of the Delay pin on LM2597M-ADJ/NOPB?

On LM2597M-ADJ/NOPB, the Delay pin sets the time interval between when VOUT reaches 95% of its target value and when the Error_Flag output transitions high-preventing premature system initialization. A capacitor (typically 10–100 nF) between Delay and GND creates this delay; larger values increase hold-off time linearly. This ensures microprocessors receive a clean, delayed power-good signal synchronized to actual regulation stability.

Does LM2597M-ADJ/NOPB require external compensation components?

No, LM2597M-ADJ/NOPB includes fully internal frequency compensation-no external capacitors or resistors are needed for loop stability. This simplifies design and eliminates tuning effort. The IC is optimized for standard buck configurations using recommended inductor and capacitor values from the datasheet (e.g., 100–150 μH inductor, 100 μF output capacitor). Layout adherence to TI's guidelines remains critical for noise immunity and thermal performance.