Analog Devices Inc./Maxim Integrated MAX17681AATB+

Overview

MAX17681AATB+ from Maxim Integrated is a high-voltage, isolated synchronous buck (iso-buck) DC-DC converter IC delivering up to 5W of isolated power with primary-side feedback regulation. 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 supports robust secondary-side overcurrent protection - a key enhancement over the MAX17681. It is used in isolated fieldbus interfaces and PLC I/O modules requiring compact, optocoupler-free isolation.

For engineers reviewing the MAX17681AATB+ datasheet, MAX17681AATB+ pinout, MAX17681AATB+ application, or MAX17681AATB+ equivalent, this page delivers verified technical context, exact pin functions, confirmed 10-pin TDFN (3mm × 2mm) package mapping, five critical operating parameters (4.5–42V input, 1.65A peak current limit, 200kHz switching frequency, ±1.7% FB accuracy, -40°C to +125°C operation), and two validated alternative parts with documented functional differences.

Technical Context

The MAX17681AATB+ implements peak-current-mode control with integrated high-side pMOS and low-side nMOS power switches, enabling primary-side regulation without optocouplers. Its internal 5V LDO (VCC) supplies gate drivers and logic, with 40mA typical sourcing capability and 3.7V UVLO.

It features programmable EN/UVLO (1.218V rising threshold), adjustable soft-start via external capacitor, and dual-stage overcurrent protection: cycle-by-cycle peak limit (1.65A typ), runaway limit (1.7A typ), and - uniquely in the 'A' variant - 16-consecutive-negative-current-event detection for reliable secondary-side short-circuit response and controlled hiccup-mode recovery.

Key Specifications

Pinout & Package

MAX17681AATB+ is housed in a 10-pin, 3mm × 2mm TDFN package with exposed pad (EP) connected to GND for thermal management. Pin pitch is 0.5mm; land pattern follows JEDEC MO-229 variation WAAB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX17681ATB+, the MAX17681AATB+ adds deterministic secondary short-circuit recovery and active CPRI discharge, making it the sole choice for new designs requiring robust fault tolerance. Versus LM5160QPWPRQ1, it trades flexibility for integration - eliminating optocouplers, gate drivers, and external MOSFETs to reduce footprint and improve reliability in ≤5W isolated applications.

Availability

MAX17681AATB+ is available at Aetrix Electronics and suitable for isolated fieldbus interfaces, PLC I/O modules, and smart meter designs requiring stable component supply, long-term industrial lifecycle support, and RoHS-compliant packaging.

Supply support for MAX17681AATB+ 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, communications, and computing applications.

The MAX17681A series belongs to Maxim's isolated power conversion product line, designed specifically to replace optocoupler-based feedback in low-power isolated DC-DC converters while maintaining high efficiency, small footprint, and robust fault handling.

FAQ

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

The MAX17681AATB+ introduces enhanced secondary-side overcurrent protection absent in the MAX17681ATB+. Specifically, it detects 16 consecutive negative current limit events to trigger hiccup mode, actively discharges the primary capacitor during timeout, and performs coordinated soft-start of both primary and secondary outputs upon recovery. This ensures reliable fault containment and smooth voltage restoration after secondary short circuits - a capability not present in the base MAX17681ATB+.

Does MAX17681AATB+ require an optocoupler for isolation?

No, the MAX17681AATB+ does not require an optocoupler. It uses primary-side feedback regulation: the FB pin monitors the primary-side output voltage (VPRI), which is then scaled by the transformer turns ratio to derive isolated secondary voltages. This architecture eliminates optocoupler dependency, reducing component count, cost, and long-term reliability concerns related to LED aging and CMTI degradation.

What is the maximum continuous output power supported by MAX17681AATB+?

The MAX17681AATB+ is rated for up to 5W of continuous isolated output power. This rating assumes proper thermal management (e.g., adequate PCB copper area under the exposed pad), use of recommended external components (X7R ceramics, low-leakage transformer), and operation within the -40°C to +125°C ambient temperature range. Derating applies above +70°C ambient per the 67.3°C/W θ_JA thermal resistance.

How is the soft-start time configured on MAX17681AATB+?

The soft-start time on MAX17681AATB+ is set by an external capacitor connected from the SS pin to GND. The relationship is t_SS (ms) = 5.55 × C_SS (nF). For example, a 3300pF capacitor yields ~18.3ms soft-start duration. This linear ramp controls the internal error amplifier reference, ensuring monotonic VPRI rise and limiting inrush current into the transformer primary and output capacitors.

What protection features are implemented in MAX17681AATB+?

The MAX17681AATB+ integrates multiple protection features: cycle-by-cycle peak current limit (1.65A typ), runaway current limit (1.7A typ), sink current limit (1.25A typ), thermal shutdown (165°C with 10°C hysteresis), output undervoltage hiccup (70.5% VPRI), and - uniquely in the 'A' variant - robust secondary-side short-circuit detection via 16-consecutive-negative-current-event logic. The open-drain RESET pin also signals regulation faults and thermal shutdown events.