Analog Devices Inc./Maxim Integrated MAX6865UK28D3S+T

Overview

The MAX6865UK28D3S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 2.800V reset threshold (suffix '28'), 300ms minimum reset timeout (suffix 'D3'), and watchdog timer with 3.3s typical timeout (suffix 'S'). It monitors VCC, responds to manual reset (MR) input, and triggers reset on watchdog timeout or brownout - ideal for battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK28D3S+T datasheet, MAX6865UK28D3S+T pinout, MAX6865UK28D3S+T application, or MAX6865UK28D3S+T equivalent, key selection criteria include its guaranteed reset validity down to VCC = +1.1V, immunity to short VCC transients (<40µs at 100mV overdrive), push-pull active-high RESET output, and compatibility with 1.2V–5.5V supply rails in space-constrained, low-power embedded systems.

Technical Context

This device integrates three core functions: precision voltage monitoring with ±2.5% threshold accuracy, a manual reset input with 250ns MR-to-reset delay and internal 10kΩ pullup, and a watchdog timer that clears on any WDI edge and expires after 3.3s (typ) if inactive. Its BiCMOS process enables stable operation across –40°C to +85°C while maintaining sub-µA quiescent current.

The reset assertion logic combines VCC monitoring, MR assertion, and watchdog expiration - all forcing RESET high (active-high push-pull) for ≥300ms after recovery. The watchdog timeout is temperature-stable (±20% over full range), and reset timing is guaranteed independent of VCC slew rate above 10mV/µs.

Key Specifications

Pinout & Package

Package: 5-pin SOT23 (lead-free, +T suffix), footprint-compatible with industry-standard 5-lead SOT-23 packages; thermal pad not present.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervisory applications.

Compared with MAX6865UK28D3S+T, MAX6864UK28D3S+T offers identical supervision performance but inverted reset polarity, while TPS3836K28DBVR trades 15× higher quiescent current for lower unit cost and no watchdog capability - making MAX6865UK28D3S+T optimal for battery-critical, safety-relevant applications requiring both voltage and firmware supervision.

Availability

MAX6865UK28D3S+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, and portable MP3 players requiring stable component supply with long-term lifecycle support and lead-free compliance.

Supply support for MAX6865UK28D3S+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) designs precision analog and mixed-signal ICs for power, sensing, and connectivity in demanding industrial, medical, and consumer applications.

The MAX68xx family delivers nanopower supervisory solutions optimized for battery longevity and reliability in portable medical and handheld electronics - emphasizing ultra-low ICC, guaranteed reset validity at low VCC, and integrated watchdog functionality.

FAQ

What is the exact reset threshold voltage of the MAX6865UK28D3S+T?

The MAX6865UK28D3S+T has a factory-trimmed reset threshold voltage of 2.800V, with ±2.5% tolerance over the full –40°C to +85°C temperature range. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix '28' corresponds to VTH = 2.800V (min 2.730V, typ 2.800V, max 2.870V). The MAX6865UK28D3S+T guarantees valid reset assertion down to VCC = +1.1V regardless of threshold setting.

Does the MAX6865UK28D3S+T require external components for basic operation?

No, the MAX6865UK28D3S+T operates autonomously with no external components required. It includes an internal 10kΩ pullup on the MR pin, a precision voltage reference, and a fully integrated watchdog timer. Only a 0.1µF ceramic bypass capacitor from VCC to GND is recommended for noise immunity - this is standard practice, not a functional requirement. The MAX6865UK28D3S+T does not need external resistors, capacitors, or timing networks.

What is the function of the WDI pin on the MAX6865UK28D3S+T?

The WDI (Watchdog Input) pin on the MAX6865UK28D3S+T monitors microprocessor activity: the internal watchdog timer resets on every rising or falling edge and expires if WDI remains static for longer than 3.3s (typ). Upon timeout, it forces the active-high RESET output high for 300ms (min). The MAX6865UK28D3S+T detects pulses as short as 150ns and clears the timer immediately upon MR assertion or RESET activation - ensuring robust firmware crash recovery.

How does the MAX6865UK28D3S+T behave during short VCC transients?

The MAX6865UK28D3S+T is designed to ignore brief VCC disturbances: it withstands transients up to 100mV amplitude for ≤40µs without asserting reset, as verified in the "Maximum VCC Transient Duration vs. Reset Threshold Overdrive" graph. This immunity prevents false resets caused by switching noise or load dumps. The MAX6865UK28D3S+T guarantees correct operation even when VCC slews at rates exceeding 10mV/µs, making it suitable for electrically noisy portable equipment.

Is the MAX6865UK28D3S+T pin-compatible with other supervisory ICs?

The MAX6865UK28D3S+T uses a standard 5-pin SOT23 package with pin 1 = RESET, pin 2 = GND, pin 3 = MR, pin 4 = WDI, pin 5 = VCC - matching the MAX6864/MAX6866 pinout. It is not pin-compatible with MAX6861–MAX6863 (which use CT instead of WDI) or MAX6854–MAX6856 (which lack WDI). While functionally similar to TPS3836-series devices, the MAX6865UK28D3S+T differs in pin assignment and requires schematic review before substitution.