Analog Devices Inc./Maxim Integrated MAX1538ETI+

Overview

The MAX1538ETI+ from Maxim Integrated is a dual-battery power-source selector IC that autonomously selects between AC adapter, airline adapter, and two Li-ion battery packs based on presence detection, state-of-charge monitoring, and undervoltage thresholds. It features break-before-make switching (≤0.88 µs transition), direct P-channel MOSFET gate drive (±70 mA sink/source), 50 µA max quiescent current from highest supply, and supports relearn mode for battery capacity calibration. It is used in notebook computers requiring hot-swap-capable, aircraft-compliant power path management.

For engineers reviewing the MAX1538ETI+ datasheet, MAX1538ETI+ pinout, MAX1538ETI+ application, or MAX1538ETI+ equivalent, key selection criteria include its 4.75V–28V ADPIN input range, dual-battery undervoltage detection via MINVA/MINVB inputs, 3.3V linear regulator output (VDD), and open-drain state outputs (OUT0–OUT2) for host µP coordination.

Technical Context

The MAX1538ETI+ implements a fixed-state machine with analog comparators for ACDET (2.0 V ±20 mV threshold) and AIRDET (same threshold, mutually exclusive with ACDET), plus dual independent battery voltage monitors using 5× scaling of MINVA/MINVB reference inputs to detect undervoltage (e.g., 13.0 V trip at VMINVA = 2.6 V). It drives eight P-channel MOSFET gates-ADPPWR, REVBLK, ADPBLK, DISBAT, CHGA, CHGB, DISA, DISB-with clamp-limited turn-on voltages (−3.5 V to −11.7 V relative to source) and sub-microsecond timing (0.3–0.88 µs).

Its architecture separates power-path control from system µP firmware: logic inputs (CHRG, BATSEL, RELRN) enable charge/discharge selection and relearn mode, while three open-drain outputs (OUT0–OUT2) encode eight discrete states per Table 1-including AC charge A/B, relearn A/B, airline mode, and discharge A/B-without requiring real-time polling or interrupt handling.

Key Specifications

Pinout & Package

The MAX1538ETI+ is housed in a 28-pin thin QFN package (5 mm × 5 mm, 0.5 mm pitch) with exposed thermal pad. Pin 1 is marked by dot; pins 15 and 21 are no-connect.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power-source selector applications.

Compared with MAX1537ETI+, the MAX1538ETI+ adds full dual-battery arbitration and relearn mode; versus BQ24725ARGER, it delivers deterministic, zero-latency source selection without MCU dependency or serial bus timing constraints.

Availability

MAX1538ETI+ is available at Aetrix Electronics and suitable for notebook computers, internet tablets, and dual-battery portable equipment requiring stable component supply, hot-swap reliability, and aircraft-compliant power management.

Supply support for MAX1538ETI+ 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) designs precision analog, mixed-signal, and power-management ICs for demanding industrial, computing, and automotive applications.

The MAX1538ETI+ belongs to Maxim's battery management and power-path controller product line, engineered specifically for autonomous, multi-source power selection in portable computing platforms with dual-Li-ion battery configurations.

FAQ

What is the function of the RELRN pin on the MAX1538ETI+?

The RELRN pin on the MAX1538ETI+ enables battery relearn mode when driven high. In this mode, the MAX1538ETI+ disables the AC adapter path (via ADPPWR) and forces discharge from the selected battery (A or B, per BATSEL), allowing coulomb-counting fuel gauges to calibrate capacity. RELRN overrides CHRG and is only active when an AC adapter is present.

How does the MAX1538ETI+ detect and respond to airline adapter presence?

The MAX1538ETI+ detects airline adapter presence when VAIRDET exceeds 2.0 V while VACDET remains below 2.0 V. Upon detection, the MAX1538ETI+ disables all battery charging paths (CHGA/CHGB) and powers the system exclusively from the adapter - ensuring compliance with aviation safety regulations that prohibit in-flight battery charging.

What is the purpose of the MINVA and MINVB pins on the MAX1538ETI+?

The MINVA and MINVB pins on the MAX1538ETI+ set the undervoltage cutoff thresholds for Battery A and Battery B, respectively. Each accepts a 0.93–2.6 V reference; the MAX1538ETI+ internally scales this by 5× (e.g., 2.6 V → 13.0 V) to prevent discharge below safe Li-ion levels. Input bias current is <50 nA, enabling high-accuracy resistor-divider design.

Can the MAX1538ETI+ support both step-down and step-up battery chargers?

Yes, the MAX1538ETI+ supports both step-down and step-up/step-down battery chargers. Its DISBAT pin is optional: included for step-up chargers (to disconnect battery during charge) and omitted for step-down chargers. Figures 1 and 2 in the MAX1538ETI+ datasheet show the respective configurations, maintaining identical core selection logic in both cases.

What do the OUT0, OUT1, and OUT2 pins indicate on the MAX1538ETI+?

The OUT0, OUT1, and OUT2 pins on the MAX1538ETI+ are open-drain state outputs encoding eight possible power-path conditions (e.g., "110" = AC charge Battery A). They provide real-time status to the host µP without polling, covering AC charge, relearn, airline, discharge, and idle modes per Table 1 in the MAX1538ETI+ datasheet - enabling efficient power-management firmware.