Analog Devices Inc./Maxim Integrated MAX1687EUE+T

Overview

MAX1687EUE+T from Maxim Integrated is a step-up DC-DC converter IC designed for GSM RF power amplifier burst-load supply, featuring precise voltage-controlled current limiting, 90% peak efficiency, 2.7V–6V input range, and 1.25V–6V adjustable output. It delivers up to 2W from a single Li-Ion or three NiMH cells while limiting peak battery current to 450mA to extend battery life and minimize voltage sag in wireless handsets.

For engineers reviewing the MAX1687EUE+T datasheet, MAX1687EUE+T pinout, MAX1687EUE+T application, or MAX1687EUE+T equivalent, key selection criteria include its adaptive current-limit architecture (distinct from MAX1688's constant-recharge-time), TSSOP-16 package with dual power-ground pins, synchronous rectification eliminating external Schottky diodes, 3µA shutdown current, and logic-controlled standby mode synchronized to RF transmit bursts.

Technical Context

The MAX1687EUE+T implements hysteretic inductor-current control with programmable peak current via the LIM pin (0–1V input), enabling precise battery current regulation during GSM 12% duty-cycle bursts. Its four-phase startup sequence-Linear Regulator → Pseudo Buck → Pseudo Boost → Boost-limits inrush current and maintains stable battery voltage during power-up.

It integrates internal P- and N-channel MOSFETs (0.3Ω/0.7Ω typical on-resistance), a 1.25V reference (±2.2% over temperature), and feedback transconductance of 200µA/V. Output disconnect during shutdown isolates the reservoir capacitor from the input, and the ON pin provides both standby (inductor current ramp-down) and full shutdown (<3µA) modes with 1.2ms timeout.

Key Specifications

Pinout & Package

MAX1687EUE+T is housed in a 16-pin thin-shrink small-outline package (TSSOP), 1.1mm max height, with exposed thermal pad (not electrically connected). Pin layout separates analog ground (AGND) and power ground (PGND) for noise isolation in high-dI/dt switching paths.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX1688EUE+T, the MAX1687EUE+T offers superior control over absolute battery current during bursts - essential for Li-Ion impedance management - while TPS61088RHLR trades GSM-specific features for higher power and input flexibility, requiring additional timing logic for RF-noise mitigation.

Availability

MAX1687EUE+T is available at Aetrix Electronics and suitable for GSM handset design, wireless LAN client integration, and PCMCIA power socket development requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.

Supply support for MAX1687EUE+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, communications, and consumer applications.

The MAX1687EUE+T belongs to Maxim's GSM-optimized power management product line, engineered specifically to address battery surge current, RF noise coupling, and burst-load efficiency challenges in 2G mobile infrastructure and handheld devices.

FAQ

What is the primary function of the LIM pin on the MAX1687EUE+T?

The LIM pin on the MAX1687EUE+T sets the peak battery current limit via an applied 0–1V analog voltage. At 0–0.25V, current limit is fixed at 200mA; above 0.25V, ILIM = VLIM × 0.86A/V – 0.06A, enabling precise control up to 450mA. This feature is unique to the MAX1687EUE+T and distinguishes it from the MAX1688EUE+T, which uses the CHG pin for adaptive recharge timing instead.

Does the MAX1687EUE+T support true shutdown or only standby mode?

The MAX1687EUE+T supports both modes: pulling the ON pin low for <1.2ms activates standby mode (output capacitor powers the load, inductor current ramps to zero), while holding ON low for >1.2ms triggers full shutdown with 3µA quiescent current. In shutdown, the device disconnects OUT from IN and disables all internal circuitry - a confirmed behavior documented in the MAX1687EUE+T datasheet Section "Standby/Shutdown".

Can the MAX1687EUE+T operate with an input voltage below 2.7V?

No - the MAX1687EUE+T has a guaranteed operational input range of 2.7V to 6V, with undervoltage lockout (UVLO) activating below ~2.35V (min) as specified in the Electrical Characteristics table. Operation below 2.7V is not characterized or supported; attempting to power the MAX1687EUE+T from a deeply discharged Li-Ion cell (<2.7V) will result in UVLO latch-off and no output regulation.

How does the MAX1687EUE+T achieve 90% efficiency without an external Schottky diode?

The MAX1687EUE+T achieves 90% efficiency through integrated synchronous rectification: it contains both high-side P-channel and low-side N-channel MOSFETs (0.3Ω/0.7Ω typical R_DS(on)) that replace the lossy external Schottky diode. This eliminates forward-voltage drop (~0.3–0.5V) losses and reduces conduction loss, especially at high load currents - a key efficiency advantage confirmed in Typical Operating Characteristics Figure toc01.

Is the MAX1687EUE+T pin-compatible with the MAX1688EUE+T?

Yes - the MAX1687EUE+T and MAX1688EUE+T share identical TSSOP-16 pinouts and footprints, including IN, OUT, LX1, LX2, FB, REF, ON, AGND, PGND, GND, and LIM/CHG pin assignments. However, LIM (MAX1687EUE+T) and CHG (MAX1688EUE+T) serve different functions and are not functionally interchangeable without circuit redesign - mechanical compatibility does not imply electrical or functional drop-in replacement.