Analog Devices Inc./Maxim Integrated MAX6865UK31D2S+T

Overview

The MAX6865UK31D2S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 3.075V reset threshold (suffix "31"), 40ms minimum reset timeout (suffix "D2"), and watchdog timer with 3.3s typical timeout (suffix "S"). It monitors VCC, responds to manual reset (MR), and triggers reset on watchdog timeout or brownout - used in battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK31D2S+T datasheet, MAX6865UK31D2S+T pinout, MAX6865UK31D2S+T application, or MAX6865UK31D2S+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 noisy low-power systems requiring long battery life.

Technical Context

The MAX6865UK31D2S+T integrates voltage monitoring, manual reset input (MR), and watchdog timer (WDI) in a single BiCMOS IC. Its reset logic asserts RESET high when VCC falls below 3.075V, MR is pulled low, or WDI remains static beyond 3.3s (typ); reset remains asserted for ≥40ms after recovery.

It uses internal 10kΩ MR pullup, accepts CMOS-level MR/WDI inputs, and guarantees valid RESET output down to VCC = +1.1V. The push-pull active-high RESET output is referenced to VCC and sinks ≤0.3V at 1.2mA load, enabling direct interface with µP reset inputs without external components.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, -40°C to +85°C operating range.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6865UK31D2S+T, the MAX6864UK31D2S+T offers identical timing and threshold but inverted RESET polarity, while the TPS3837K33DBVR trades nanopower and watchdog capability for lower unit cost and simpler qualification in non-safety-critical consumer gear.

Availability

MAX6865UK31D2S+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered instrumentation, industrial handheld terminals, and low-power IoT edge nodes requiring stable component supply across extended product lifecycles.

Supply support for MAX6865UK31D2S+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 and medical applications.

The MAX68xx family delivers nanopower supervisory circuits optimized for battery longevity and reliability in portable healthcare and instrumentation - addressing critical needs for brownout immunity, watchdog safety, and minimal footprint.

FAQ

What is the exact reset threshold voltage of the MAX6865UK31D2S+T?

The MAX6865UK31D2S+T has a factory-trimmed reset threshold of 3.075V, with ±2.5% tolerance over -40°C to +85°C. This value is defined by the "31" suffix per Maxim's Threshold Suffix Guide (Table 2), and is guaranteed across temperature and supply voltage variations. The MAX6865UK31D2S+T uses this precise threshold to detect brownout on 3.0V–3.3V rails without external resistive dividers.

Does the MAX6865UK31D2S+T require external components for basic operation?

No, the MAX6865UK31D2S+T operates autonomously with no external components required. It integrates a 10kΩ internal pullup on MR, precision bandgap reference, watchdog oscillator, and push-pull active-high RESET driver. Only a 0.1µF ceramic capacitor from VCC to GND is recommended for noise suppression - no resistors, capacitors, or diodes are needed for reset generation, manual reset, or watchdog functionality in the MAX6865UK31D2S+T.

How does the watchdog timer in the MAX6865UK31D2S+T function?

The MAX6865UK31D2S+T watchdog timer expires if the WDI pin remains static (high or low) for longer than 3.3s (typical). A rising or falling edge on WDI clears the timer. When expired, it asserts the active-high RESET output for ≥40ms. The timer pauses while RESET is asserted and resumes counting upon deassertion. This behavior ensures reliable detection of firmware hangs without requiring complex software pulse patterns in the MAX6865UK31D2S+T.

Can the MAX6865UK31D2S+T operate reliably below 1.8V?

Yes, the MAX6865UK31D2S+T is fully specified from VCC = 1.2V to 5.5V and guarantees RESET output validity down to VCC = +1.1V. At 1.2V, supply current remains ~190nA (typ), and RESET maintains VOH ≥0.8×VCC and VOL ≤0.3V under load. This allows robust operation in deeply discharged Li-ion or alkaline battery systems where other supervisors fail - a core design feature of the MAX6865UK31D2S+T.

What is the meaning of the "D2S" suffix in MAX6865UK31D2S+T?

In MAX6865UK31D2S+T, "D2" denotes the 40ms minimum reset timeout period (per Table 4), and "S" specifies the 3.3s typical watchdog timeout (per Table 3). The "31" indicates the 3.075V reset threshold. Together, these suffixes define the device's timing behavior: it holds RESET high for ≥40ms after VCC recovery or MR release, and triggers reset if WDI is inactive for >3.3s. This exact configuration is unique to the MAX6865UK31D2S+T.