Analog Devices Inc./Maxim Integrated MAX1687ESA+T

Overview

MAX1687ESA+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 MAX1687ESA+T datasheet, MAX1687ESA+T pinout, MAX1687ESA+T application, or MAX1687ESA+T equivalent, key selection considerations include its adaptive burst-mode operation, 3µA shutdown current, synchronous rectification, internal MOSFETs and sense resistor, and SO-8 package compatibility with GSM handset power architecture.

Technical Context

The MAX1687ESA+T implements hysteretic inductor-current control with programmable peak current via the LIM pin (0–1V input), enabling precise battery current regulation during 12% duty-cycle GSM bursts. Its four-phase startup sequence-Linear Regulator, Pseudo Buck, Pseudo Boost, and Boost Mode-limits inrush current and maintains stable V_OUT slope during power-up.

It integrates dual N/P-channel MOSFETs, an internal current-sense resistor, and analog ground (AGND) / power ground (PGND) separation to suppress noise coupling. The device supports synchronized standby mode via the ON pin, disconnecting output from input during RF transmit to eliminate switching noise and allow reservoir capacitor discharge.

Key Specifications

Pinout & Package

MAX1687ESA+T is housed in an 8-pin SO (Small Outline) package with 1.27mm pitch, 1.75mm max height, and Pb-free lead finish. Thermal performance supports 471mW continuous dissipation at +70°C (derated 5.88mW/°C above).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX1688ESA+T, the MAX1687ESA+T offers deterministic current limiting via analog LIM voltage but requires external control logic for dynamic adaptation; compared with TPS61040DRVR, it provides lower shutdown current, integrated sensing, and noise-suppressing standby mode essential for RF-critical designs.

Availability

MAX1687ESA+T is available at Aetrix Electronics and suitable for GSM handset design, wireless PC card development, and portable medical telemetry systems requiring stable component supply, long-lifecycle support, and guaranteed parametric compliance across –40°C to +85°C.

Supply support for MAX1687ESA+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 MAX1687ESA+T belongs to Maxim's GSM-optimized power management product line, engineered specifically to address battery current surge, RF noise coupling, and thermal constraints in cellular handset power architectures.

FAQ

What is the maximum output current capability of the MAX1687ESA+T?

The MAX1687ESA+T delivers up to 2W of output power. At 5V output, this corresponds to 400mA continuous load; under GSM burst conditions (12% duty cycle), it supports peak currents up to 2A by drawing energy from the external reservoir capacitor. Peak battery current is limited to 450mA via the LIM pin, ensuring safe operation with single Li-Ion cells. The actual sustained current depends on input voltage, output voltage, and thermal conditions.

Does the MAX1687ESA+T require an external Schottky diode?

No, the MAX1687ESA+T does not require an external Schottky diode. It integrates synchronous rectification using internal N- and P-channel MOSFETs, which replace the conventional diode and improve conversion efficiency to over 90%. This integration reduces component count, board area, and conduction losses-critical advantages in space-constrained GSM handset designs where thermal management is challenging.

How does the ON pin function in the MAX1687ESA+T?

The ON pin on the MAX1687ESA+T is a logic-level control input that enables normal operation when pulled high (VIH ≥ 1.8V) and initiates standby mode when pulled low. If held low for longer than 1.2ms, the device enters shutdown mode with only 3µA supply current. During standby, the output disconnects from the input, allowing the reservoir capacitor to power the RF amplifier without switching noise-making it ideal for synchronizing with GSM transmit windows.

Can the MAX1687ESA+T operate with a 2.5V input supply?

No, the MAX1687ESA+T cannot reliably operate with a 2.5V input. Its absolute minimum input voltage is 2.7V, as specified in the Electrical Characteristics table and validated across the –40°C to +85°C temperature range. Operation below 2.7V may cause undervoltage lockout activation or unstable regulation. For 2.5V systems, consider alternative boost converters with lower VIN(min) such as the MAX1722 or TPS61200, which specify 0.3V start-up and 0.9V minimum operating voltage.

What is the purpose of the LIM pin on the MAX1687ESA+T?

The LIM pin on the MAX1687ESA+T provides analog control of the peak inductor current-and thus the peak battery current-via a 0–1V input voltage. Applying 0.25–1V sets ILIM from 200mA to 450mA using the formula ILIM = VLIM × 0.86A/V – 0.06A. This enables precise battery current management during RF bursts, optimizing trade-offs between reservoir capacitor size, battery lifetime, and voltage sag. The pin is internally clamped to 1.25V to prevent overrange damage.