Analog Devices Inc./Maxim Integrated MAX17681AATB+T

Overview

MAX17681AATB+T from Maxim Integrated is a high-voltage, isolated synchronous buck (iso-buck) DC-DC converter IC delivering up to 5W isolated output power using primary-side feedback. It operates from 4.5V to 42V input, integrates low-R_DS(on) pMOS and nMOS switches (0.85Ω/0.35Ω typ at +25°C), and features peak-current-mode control with 200kHz switching frequency. It is used in isolated fieldbus interfaces and PLC I/O modules requiring robust secondary-side overcurrent protection.

For engineers reviewing the MAX17681AATB+T datasheet, MAX17681AATB+T pinout, MAX17681AATB+T application, or MAX17681AATB+T equivalent, key selection considerations include its 10-pin TDFN (3mm × 2mm) package, ±1.7% FB regulation accuracy, 90%+ peak efficiency, programmable EN/UVLO threshold (1.218V typ), and enhanced hiccup-mode recovery for secondary short-circuit events - critical for medical and industrial isolation designs.

Technical Context

The MAX17681AATB+T implements peak-current-mode control with internal transconductance amplifier (GM = 590μS typ) and dual current-limit sensing (peak: 1.65A typ; sink: 1.25A typ; runaway: 1.7A typ). Its iso-buck topology eliminates optocouplers by regulating primary-side voltage (0.9V to 0.96×V_IN) and scaling it via transformer turns ratio to generate isolated outputs.

It integrates an internal 5V LDO (V_CC, 40mA max) for gate drive and logic, supports adjustable soft-start (5μA SS charge current), and delivers open-drain RESET with 92.5%/95.5% FB thresholds and 1024-cycle delay. Thermal shutdown activates at +165°C with 10°C hysteresis, and operation spans –40°C to +125°C junction temperature.

Key Specifications

Pinout & Package

MAX17681AATB+T is housed in a thermally enhanced 10-pin TDFN package (3mm × 2mm, exposed pad), optimized for high-density PCB layouts and efficient heat dissipation via the EP-to-GND connection.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar iso-buck DC-DC converter applications.

Compared with MAX17681ATB+T, the MAX17681AATB+T adds deterministic secondary short-circuit recovery via 16-cycle negative current detection and active primary capacitor discharge - a critical differentiator for medical and functional-safety applications. Versus LM5160QPWPRQ1, it trades off flexibility for integration, reducing bill-of-materials by ~7 components and eliminating optocoupler aging concerns.

Availability

MAX17681AATB+T is available at Aetrix Electronics and suitable for isolated fieldbus interfaces, PLC I/O modules, and smart meter auxiliary power supplies requiring stable component supply, long-lifecycle assurance, and RoHS-compliant packaging.

Supply support for MAX17681AATB+T 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

Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and communications markets.

The MAX17681A product line delivers integrated iso-buck DC-DC converters targeting space-constrained, high-reliability industrial isolation applications - designed to replace optocoupler-based flyback solutions with simplified, high-efficiency, and thermally robust alternatives.

FAQ

What is the key functional difference between MAX17681AATB+T and MAX17681ATB+T?

The MAX17681AATB+T implements enhanced secondary-side overcurrent protection not present in MAX17681ATB+T. Specifically, MAX17681AATB+T enters hiccup mode after detecting 16 consecutive negative current limit events - enabling reliable recovery from secondary short circuits. In contrast, MAX17681ATB+T only responds to primary-side faults or VPRI undervoltage, making MAX17681AATB+T the recommended choice for safety-critical isolation applications.

Does MAX17681AATB+T require an optocoupler for isolation feedback?

No, MAX17681AATB+T does not require an optocoupler. It uses primary-side feedback to regulate the primary output voltage (VPRI), which is then scaled by the transformer turns ratio to produce the isolated secondary output. This architecture eliminates optocouplers, reducing component count, cost, and long-term drift issues associated with optocoupler aging - a core benefit confirmed in the device's "Benefits and Features" section.

What is the maximum duty cycle and minimum on-time specification for MAX17681AATB+T?

The MAX17681AATB+T has a maximum duty cycle of 97.5% (typ) and a minimum on-time of 300ns (typ). These parameters are critical for designing the transformer turns ratio and ensuring stable operation across the full 4.5V–42V input range - especially at low input voltages where high duty cycle is needed to maintain output regulation, and at high frequencies where short on-times affect light-load performance.

How does the RESET pin on MAX17681AATB+T behave during thermal shutdown?

During thermal shutdown, the RESET pin on MAX17681AATB+T pulls low, providing a system-level fault indicator. This behavior is explicitly documented in the "RESET Output" section: "RESET also goes low during thermal shutdown." The pin remains low until the junction temperature cools by 10°C and the device resumes normal operation, at which point RESET returns high-impedance after 1024 switching cycles once FB rises above 95.5% of regulation.

What package type and thermal resistance does MAX17681AATB+T use?

MAX17681AATB+T uses a 10-pin TDFN package (3mm × 2mm) with exposed pad (EP), designated as T1032N+1. Its thermal resistance is θ_JA = 67.3°C/W and θ_JC = 18.2°C/W on a four-layer board, per JEDEC JESD51-7. The exposed pad must be soldered to a GND-connected copper plane to achieve rated thermal performance - essential for sustaining 5W output in industrial ambient temperatures up to +85°C.