Texas Instruments LM26400YSDX

Overview

LM26400YSDX from Texas Instruments is a dual-output, monolithic synchronous buck regulator IC with two integrated 175-mΩ NMOS power switches, operating across 3 V to 20 V input and delivering up to 2 A per channel at output voltages as low as 0.6 V. It employs peak current-mode control, fixed 500-kHz PWM switching, and internal compensation-enabling compact, high-efficiency point-of-load regulation in space-constrained DTV-LCD and industrial control systems.

For engineers reviewing the LM26400YSDX datasheet, LM26400YSDX pinout, LM26400YSDX application, or LM26400YSDX equivalent, key selection criteria include its dual independent enable/soft-start pins, frequency foldback protection under overload, 40-ns minimum on-time for low-VOUT operation, and thermal shutdown at 165°C-critical for robustness in automotive and computing peripheral power rails.

Technical Context

The LM26400YSDX integrates two identical peak-current-mode buck regulators sharing AVIN and a common 0.6-V reference, but operating with 180° phase-shifted clocks to reduce input ripple. Each channel features independent ENx and SSx pins, enabling staggered startup and selective shutdown without affecting the other output.

Its internal compensation network is optimized for ceramic output capacitors, with loop stability targeting 20–100 kHz crossover. Frequency foldback activates below 0.35 V FB voltage to prevent runaway current during overloads, while thermal shutdown (165°C) and pulse-by-pulse current limiting (3 A typical) provide layered fault protection.

Key Specifications

Pinout & Package

LM26400YSDX is packaged in a thermally enhanced 16-pin HTSSOP (PWP) with exposed PowerPAD (4.4 mm × 5.0 mm), optimized for high-power density and low junction-to-board thermal resistance (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 LM26400YSDX, LM26420YSDX offers higher current capability in identical packaging, while TPS54290PWPR trades integration for higher switching frequency and design flexibility-making LM26400YSDX optimal for cost-sensitive, thermally constrained 2-A dual-rail applications requiring minimal external parts.

Availability

LM26400YSDX is available at Aetrix Electronics and suitable for DTV-LCD, automotive infotainment, and industrial PLC applications requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for LM26400YSDX 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 and embedded processing technologies, with decades of expertise in power management IC design and high-volume manufacturing reliability.

The LM26400Y product line delivers highly integrated, easy-to-use dual buck regulators targeting space- and thermal-constrained point-of-load applications in consumer, industrial, and automotive electronics.

FAQ

What is the recommended input capacitor for LM26400YSDX in a 12-V input application?

For a 12-V input, TI recommends a 10-µF, 16-V X5R/X7R ceramic capacitor (e.g., Murata GRM32DR61C106KA01) placed close to the PVIN and GND pins. This value provides sufficient bulk capacitance and low ESR to handle 500-kHz ripple current while minimizing voltage droop during load transients. Additional 0.1-µF and 0.22-µF ceramics in parallel improve high-frequency decoupling at the AVIN and BST pins. The LM26400YSDX datasheet specifies these values in Table 1 of the Typical Applications section.

Does LM26400YSDX support output prebias startup?

Yes, LM26400YSDX can start up into a prebiased output if the input-to-output voltage difference is at least 2 V. This behavior is confirmed in Section 7.4.1 of the LM26400YSDX datasheet, which states successful startup occurs under prebias conditions when VIN − VOUT ≥ 2 V. The internal bootstrap capacitor retains sufficient charge during brief brownouts, making LM26400YSDX suitable for systems with hot-swap or redundant supply architectures.

How does frequency foldback operate in LM26400YSDX during overload?

In LM26400YSDX, frequency foldback activates when the FB pin voltage drops below 0.35 V, reducing switching frequency proportionally to limit thermal stress and prevent current runaway. As shown in Figure 10 of the datasheet, frequency decreases from 500 kHz to ~100 kHz as FB falls from 0.35 V to 0.1 V. This mechanism protects both the IC and external components during sustained overload or short-circuit events without requiring external circuitry.

Can EN1 and EN2 pins of LM26400YSDX be tied together?

Yes, EN1 and EN2 pins of LM26400YSDX may be tied together to enable simultaneous startup of both channels, provided the shared enable signal meets logic thresholds: ≥2.5 V for turn-on and ≤0.4 V for turn-off. However, tying them forfeits independent sequencing capability. The LM26400YSDX datasheet explicitly permits this configuration in the Pin Functions table, noting that each EN pin is independently buffered and electrically isolated internally.

What is the maximum achievable output voltage accuracy for LM26400YSDX?

The LM26400YSDX achieves ±1.5% output voltage accuracy over temperature (–40°C to 125°C) and line/load conditions, based on its 0.6-V feedback reference tolerance (0.585 V to 0.617 V). This accuracy assumes proper resistor divider layout (Kelvin-connected to GND), low-noise routing, and use of 0.5% or better tolerance resistors. The Electrical Characteristics table (Section 6.5) confirms this specification under "VFB" parameter with min/max limits across full operating range.