Analog Devices Inc./Maxim Integrated MAX17687ATP+

Overview

MAX17687ATP+ from Maxim Integrated is a high-voltage, isolated synchronous buck (iso-buck) DC-DC converter IC designed for primary-side regulated isolated power supplies up to 10W. It operates from 4.5V to 60V input, delivers up to 3.2A peak primary current, regulates output voltage within ±1.2% over –40°C to +125°C, and integrates low-R_DS(on) on-chip MOSFETs (165mΩ high-side, 80mΩ low-side). It is used in industrial process control systems requiring compact, high-efficiency isolated bias rails.

For engineers reviewing the MAX17687ATP+ datasheet, MAX17687ATP+ pinout, MAX17687ATP+ application, or MAX17687ATP+ equivalent, key selection considerations include its 4.5–60V input range, programmable 100–500kHz switching frequency via RT pin, primary-side feedback architecture eliminating optocouplers, open-drain RESET with 1024-cycle delay, and 20-pin 4mm × 4mm TQFN package with exposed thermal pad.

Technical Context

The MAX17687ATP+ implements peak-current-mode PWM control with internal slope compensation and hiccup-mode overcurrent protection triggered by runaway current (>3.7A), FB undervoltage (<0.58V), or 16 consecutive valley-limit events. Its primary-side regulation relies on integrated current sensing and an error amplifier referenced to the FB pin (0.90V nominal regulation point).

It integrates a 5V LDO (VCC) capable of sourcing 26.5–100mA, features programmable EN/UVLO (1.215V rising threshold), soft-start via external capacitor on SS pin (5µA charging current), and supports external synchronization (SYNC) across 1.1×–1.4× the RT-set frequency. Thermal shutdown activates at 165°C with 10°C hysteresis.

Key Specifications

Pinout & Package

Package: 20-pin TQFN (4mm × 4mm, 0.5mm pitch) with exposed thermal pad (EP), RoHS-compliant (suffix "+"). Thermal resistance θ_JA = 33°C/W (4-layer board).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5180QPWRQ1 and UCC28911DR, the MAX17687ATP+ offers superior integration (on-chip MOSFETs, primary-side feedback, 5V LDO), higher peak current capability (3.2A vs. 2.5A/1.2A), and smaller solution size-making it optimal for industrial and medical DC-input isolated power where board space and component count are critical.

Availability

MAX17687ATP+ is available at Aetrix Electronics and suitable for industrial process control, smart meter communication hubs, and medical equipment requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for MAX17687ATP+ 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 MAX17687ATP+ belongs to the Rainier series of isolated DC-DC converters, designed specifically to replace optocoupler-based flyback solutions with compact, high-efficiency, primary-side regulated iso-buck architectures for 10W-class isolated power.

FAQ

What is the primary function of the MAX17687ATP+ in a power supply design?

The MAX17687ATP+ functions as a high-voltage, isolated synchronous buck (iso-buck) DC-DC controller that generates regulated isolated output power up to 10W using primary-side feedback-eliminating the need for optocouplers or secondary-side voltage references. The MAX17687ATP+ integrates both high- and low-side MOSFETs, a 5V LDO, and comprehensive protection features including hiccup-mode current limiting and thermal shutdown, enabling compact, reliable isolated bias rails in industrial and medical systems.

How does the MAX17687ATP+ achieve primary-side regulation without an optocoupler?

The MAX17687ATP+ achieves primary-side regulation by measuring reflected voltage across the transformer's primary winding during the off-time of the low-side switch, combined with internal current sensing and a precision 0.90V feedback reference. This method infers secondary output voltage without optical coupling, enabling tighter regulation (±1.2%) and faster transient response than traditional optocoupler-based flyback controllers. The MAX17687ATP+ uses this architecture to simplify design, reduce BOM cost, and improve long-term stability.

What are the absolute maximum ratings for the LX pin of the MAX17687ATP+?

The LX pin of the MAX17687ATP+ has an absolute maximum rating of –0.3V to (VIN + 0.3V) relative to PGND, with a total RMS current rating of ±4A. Exceeding these limits risks permanent damage to the integrated high- and low-side MOSFETs. Layout best practices require short, low-inductance traces from LX to the transformer primary and proper grounding of the exposed thermal pad to maintain safe operation under full-load conditions. These constraints are defined in the MAX17687ATP+ datasheet Absolute Maximum Ratings table.

Can the MAX17687ATP+ be synchronized to an external clock, and what are the requirements?

Yes, the MAX17687ATP+ supports external frequency synchronization via the SYNC pin. The external clock must fall within 1.1× to 1.4× the RT-programmed switching frequency (e.g., 110–140kHz for a 100kHz base) and have a minimum high-pulse width of 50ns. This feature enables EMI reduction through spread-spectrum-like clock alignment and avoids interference with sensitive system clocks. The MAX17687ATP+ maintains stable operation during synchronization without phase jumps or lock loss, as verified in the Electrical Characteristics section.

What is the purpose of the RESET pin on the MAX17687ATP+, and how is it configured?

The RESET pin on the MAX17687ATP+ is an open-drain output that signals power-good status after successful output regulation. It asserts low when the FB voltage drops below 92.5% of its 0.90V setpoint and deasserts (high-impedance) 1024 switching cycles after FB rises above 95.0%. An external pull-up resistor (typically 10kΩ to VCC or system rail) is required. The MAX17687ATP+ also drives RESET low during thermal shutdown, providing fault indication beyond simple undervoltage conditions.