Analog Devices Inc./Maxim Integrated MAX42403AFLA+

Overview

MAX42403AFLA+ from Analog Devices is a fully integrated 36V, 3.5A synchronous buck converter in a 3mm × 3mm FC2QFN package, featuring internal high-side and low-side MOSFETs, programmable output voltage (0.8V–14V), 400kHz fixed switching frequency, and spread-spectrum EMI reduction. It delivers regulated DC power in industrial automation systems with 99% dropout operation and precision PGOOD monitoring.

For engineers reviewing the MAX42403AFLA+ datasheet, MAX42403AFLA+ pinout, MAX42403AFLA+ application, or MAX42403AFLA+ equivalent, key selection considerations include its 4.5V–36V input range, 27μA no-load quiescent current in skip mode, ±6% spread-spectrum modulation, internal soft-start (2.5ms), and robust protection suite including overtemperature, overvoltage, and hiccup-mode short-circuit response.

Technical Context

The MAX42403AFLA+ employs average current-mode control with fixed 400kHz oscillator, enabling stable regulation across wide input/output ratios and fast transient response. Its integrated 96mΩ/46mΩ (HS/LS) MOSFETs support continuous 3.5A output with minimal external components.

Operation includes selectable FPWM (via SYNC high) or automatic skip mode (SYNC low), plus SPS-enabled ±6% triangular spread-spectrum modulation synchronized to internal clock - disabled during external SYNC. The 1.8V BIAS LDO powers internal circuitry and requires ≥2.2μF ceramic decoupling to PGND.

Key Specifications

Pinout & Package

Package: 15-pin FC2QFN, 3mm × 3mm, 0.5mm pitch, exposed thermal pad (PGND-connected). Pinout validated per Analog Devices datasheet Rev 3 (2025).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX42402AFLA+, the MAX42403AFLA+ provides 40% higher output current headroom while retaining identical pinout, feedback architecture, and protection features - making it ideal for future-proofing industrial designs. Versus LM61480RQR, MAX42403AFLA+ integrates spread-spectrum and tighter PGOOD tolerances at the expense of non-selectable frequency.

Availability

MAX42403AFLA+ is available at Aetrix Electronics and suitable for industrial automation, point-of-load regulation, and distributed DC power systems requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for MAX42403AFLA+ 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

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The MAX42402/MAX42403 product line targets space-constrained, high-reliability industrial power conversion - emphasizing integration, EMI robustness, and extended temperature operation without external compensation.

FAQ

What is the maximum output current capability of the MAX42403AFLA+?

The MAX42403AFLA+ delivers up to 3.5A continuous output current under typical thermal conditions (TA = +70°C, four-layer board). This rating assumes proper PCB copper area, thermal vias to internal ground planes, and ambient airflow. Derating applies above +70°C at 25mW/°C, and the device enters thermal shutdown at 175°C junction temperature. The MAX42403AFLA+ achieves this with integrated 96mΩ/46mΩ MOSFETs and optimized thermal pad design in its 3mm × 3mm FC2QFN package.

Does the MAX42403AFLA+ support external frequency synchronization?

Yes, the MAX42403AFLA+ supports external clock synchronization via the SYNC pin. When an external clock signal within the specified range (360–600kHz for 400kHz mode) is applied, the device synchronizes to the rising edge within two cycles. If the external clock is absent for more than two cycles, MAX42403AFLA+ automatically reverts to its internal 400kHz oscillator. This feature enables deterministic EMI alignment in multi-converter systems without requiring additional timing circuitry.

How does the PGOOD function work on the MAX42403AFLA+?

The MAX42403AFLA+ features a windowed open-drain PGOOD output that asserts high when VOUT is within 93–105% of its nominal value (e.g., 3.07–3.32V for a 3.3V rail). It pulls low during undervoltage (falling below 93%) or overvoltage (rising above 105%), with 180μs rising and 70μs falling debounce times in 1.5MHz mode. A 20kΩ pull-up resistor to BIAS or external supply is required. This precise windowing enables reliable power sequencing in safety-critical industrial controllers.

Can the MAX42403AFLA+ operate in dropout mode, and what is the minimum input-to-output differential?

Yes, the MAX42403AFLA+ supports dropout operation with up to 99% duty cycle, enabling regulation when input voltage approaches output voltage. At 3.3V output, the minimum VSUP–VOUT differential is approximately 360mV (calculated from RDSON_HS × ILOAD + diode drop). This allows stable 24V-to-23.5V conversion in industrial brownout scenarios. Dropout behavior is automatic - no mode selection required - and maintains PGOOD assertion as long as VOUT remains within specification.

What protection features are integrated into the MAX42403AFLA+?

The MAX42403AFLA+ integrates overtemperature shutdown (175°C, 15°C hysteresis), output overvoltage protection (discharges rail via low-side FET), cycle-by-cycle overcurrent limiting (4.375–6.2A threshold), and hiccup-mode short-circuit response (35ms off-time). It also includes BIAS UVLO (1.58–1.68V), EN UVLO with hysteresis, and ESD protection (±2kV HBM). These protections operate autonomously without external components, ensuring robust operation in harsh industrial environments where the MAX42403AFLA+ is deployed.