Texas Instruments LM26400YSD/NOPB

Overview

LM26400YSD/NOPB from Texas Instruments is a monolithic dual-output synchronous buck regulator IC with two integrated 175-mΩ NMOS power switches, 500-kHz fixed-frequency PWM operation, 3 V to 20 V input range, and independent 2-A per channel capability. It delivers regulated outputs down to 0.6 V using peak current-mode control and internal compensation-designed for high-power-density point-of-load conversion in space-constrained industrial and computing systems.

For engineers reviewing the LM26400YSD/NOPB datasheet, LM26400YSD/NOPB pinout, LM26400YSD/NOPB application, or LM26400YSD/NOPB equivalent, key selection considerations include dual-channel enable/soft-start independence, frequency foldback under overcurrent, thermal shutdown at 165°C, and compatibility with ceramic output capacitors without external loop compensation.

Technical Context

The LM26400YSD/NOPB implements peak current-mode control with built-in transconductance error amplifiers and internal compensation networks optimized for ceramic output capacitors. Its dual channels share a common 0.6-V reference but operate with 180° phase-shifted switching clocks to reduce input ripple and thermal stress.

Each channel features independent EN and SS pins, programmable soft-start via external capacitor, and frequency foldback triggered when FB voltage drops below 0.35 V-enabling stable current limiting during overload without runaway switch conduction. The 40-ns minimum on-time supports high step-down ratios across the full 3–20 V input range.

Key Specifications

Pinout & Package

LM26400YSD/NOPB is packaged in a thermally enhanced 16-pin HTSSOP (PWP) with PowerPAD, measuring 4.40 mm × 5.00 mm. The exposed die attach pad (DAP) must be soldered to a large PCB copper area for optimal thermal performance (R_θJB = 18°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS54290RGER, LM26400YSD/NOPB offers simpler implementation with integrated bootstrap diodes and internal compensation, while LM26420QMHX/NOPB provides identical functionality with automotive qualification-making it the drop-in replacement where AEC-Q100 compliance is mandatory.

Availability

LM26400YSD/NOPB is available at Aetrix Electronics and suitable for DTV-LCD, industrial PLC I/O modules, and automotive infotainment head units requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM26400YSD/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 company specializing in analog, embedded processing, and power management technologies, with leadership in high-reliability DC-DC conversion solutions.

The LM26400Y series was developed for high-density dual-output point-of-load regulation in industrial, computing, and automotive systems-emphasizing ease of use, thermal robustness, and minimal external component count.

FAQ

What is the recommended input capacitor configuration for LM26400YSD/NOPB?

The LM26400YSD/NOPB requires a low-ESR ceramic input capacitor placed close to the PVIN and GND pins. TI recommends a 10-µF X5R/X7R MLCC in 1210 case size, supplemented by a 0.22-µF 0603 ceramic for high-frequency noise suppression. This configuration ensures stable operation across the 3–20 V input range and prevents voltage droop during high-current transients. The LM26400YSD/NOPB datasheet specifies these values in Table 1 of the Typical Applications section.

Does LM26400YSD/NOPB support pre-biased output startup?

Yes, LM26400YSD/NOPB can start up into a pre-biased output if the input-to-output voltage difference is ≥2 V. This capability is confirmed in Section 7.4.1 of the datasheet, which states successful startup occurs under prebias conditions when sufficient initial voltage exists across the bootstrap capacitor. However, designers should verify behavior under worst-case prebias (e.g., 12-V output with 12-V input) using bench testing, as the LM26400YSD/NOPB does not include active prebias protection circuitry.

How does frequency foldback function in LM26400YSD/NOPB during overload?

In LM26400YSD/NOPB, frequency foldback activates when the FB pin voltage falls below 0.35 V-indicating severe output droop due to overload. The switching frequency decreases linearly as FB drops further, reducing thermal stress on both the IC and external components. This mechanism prevents minimum-on-time violation at low duty cycles and avoids runaway current in the internal 175-mΩ NMOS switch. The behavior is documented in Figure 10 and Section 7.3.1 of the LM26400YSD/NOPB datasheet.

Can LM26400YSD/NOPB operate with only ceramic output capacitors?

Yes, LM26400YSD/NOPB is explicitly optimized for ceramic output capacitors, with internal compensation tuned for their low ESR and high self-resonant frequency. The datasheet recommends X5R or X7R dielectrics (e.g., 36 µF total for 2.5-V output) and warns against Z5U/Y5F types due to capacitance loss under bias and temperature. No external compensation components are needed-confirmed in Section 7.1 and Application Note SNVA221.

What is the thermal performance difference between HTSSOP and WSON packages for LM26400YSD/NOPB?

The WSON package (NHQ) offers superior thermal performance: R_θJB = 9.9°C/W vs 18°C/W for HTSSOP (PWP), and R_θJA = 27.8°C/W vs 39.4°C/W. This 30% lower junction-to-board resistance makes WSON preferable for high-ambient or high-power-density applications. Both packages require soldering the DAP to a thermal pad, but WSON's smaller footprint (5.0 × 5.0 mm) also reduces board area. These values are specified in Section 6.4 of the LM26400YSD/NOPB datasheet.