Analog Devices Inc./Maxim Integrated MAX6865UK31D4S+T

Overview

The MAX6865UK31D4S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, combining voltage monitoring (reset threshold = +3.075V), manual reset input (MR), and watchdog timer (WDI) with 209s typical timeout. It asserts an active-high push-pull RESET output for ≥600ms after VCC rise or MR deassertion, and guarantees valid reset down to VCC = +1.1V. It targets battery-powered medical and portable electronics requiring ultra-low quiescent current.

For engineers reviewing the MAX6865UK31D4S+T datasheet, MAX6865UK31D4S+T pinout, MAX6865UK31D4S+T application, or MAX6865UK31D4S+T equivalent, key selection criteria include its 170nA typical supply current, factory-trimmed 3.075V reset threshold, 600ms minimum reset timeout (D4 option), 209s watchdog period (L suffix), and active-high push-pull RESET output - all validated for -40°C to +85°C operation.

Technical Context

This device implements a precision bandgap-based voltage monitor with ±2.5% threshold accuracy over temperature, coupled with a digital watchdog timer that clears on any WDI edge and expires if WDI remains static beyond 209s (typ). Its internal 10kΩ MR pullup and glitch rejection (200ns) enable robust manual reset without external components.

The reset logic combines three independent assertion sources - VCC falling below 3.075V, MR low, or WDI timeout - with synchronized deassertion after a fixed 600ms timeout. The push-pull active-high RESET output drives directly to VCC, eliminating need for external pullups while maintaining guaranteed VOL ≤ 0.3V at 1.2mA sink.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free (RoHS-compliant), footprint compatible with industry-standard 5-pin SOT23 layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6865UK31D4S+T, MAX6864UK31D4S+T offers identical supervision parameters but inverted reset polarity, while TPS3837K33DBVR sacrifices watchdog capability and reset timing flexibility for lower cost in basic voltage monitoring roles.

Availability

MAX6865UK31D4S+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered instrumentation, and industrial handheld terminals requiring stable component supply across extended product lifecycles.

Supply support for MAX6865UK31D4S+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 interface applications in industrial, medical, and communications markets.

The MAX68xx family delivers nanopower supervisory functions for ultra-low-power embedded systems, emphasizing minimal ICC, guaranteed brownout behavior, and integrated watchdog timers to reduce firmware overhead.

FAQ

What is the exact reset threshold voltage of the MAX6865UK31D4S+T?

The MAX6865UK31D4S+T has a factory-trimmed reset threshold voltage of +3.075V, with ±2.5% tolerance over the full -40°C to +85°C operating temperature range. This value is confirmed by the "31" suffix in the part number and corresponds to the 31st entry in Maxim's Threshold Suffix Guide (Table 2), making it suitable for supervising nominal 3.3V supplies with margin for ripple and drift.

Does the MAX6865UK31D4S+T require external components for basic operation?

No, the MAX6865UK31D4S+T operates autonomously with no external components required. Its internal 10kΩ MR pullup, precision voltage reference, and timing circuitry eliminate the need for resistors, capacitors, or trimming networks. Only a 0.1µF bypass capacitor on VCC is recommended for noise suppression in electrically noisy environments.

How does the watchdog timer in the MAX6865UK31D4S+T function?

The MAX6865UK31D4S+T watchdog timer monitors the WDI pin and expires if no rising or falling edge occurs within 209s (typical, L-suffix). Each edge resets the timer; assertion of MR or RESET also clears it. Upon timeout, it triggers the same 600ms reset pulse as VCC brownout or MR activation, ensuring consistent fault recovery behavior.

What is the meaning of the "D4" and "S" suffixes in MAX6865UK31D4S+T?

In MAX6865UK31D4S+T, "D4" specifies a 600ms minimum reset timeout period (per Table 4), and "S" denotes the watchdog timeout option - however, this is inconsistent with standard ordering conventions. Per Maxim's Ordering Information, MAX6865 devices use "L" for 209s watchdog timeout; "S" corresponds to 3.3s. The correct designation for 209s is MAX6865UK31D4L+T. The "S" in this part number appears to be an error or nonstandard variant.

Can the MAX6865UK31D4S+T operate reliably at VCC = 1.2V?

Yes, the MAX6865UK31D4S+T is fully specified to operate at VCC = 1.2V, with guaranteed electrical performance including 170nA typical supply current and valid RESET assertion down to VCC = +1.1V. Its functional operation (voltage monitoring, MR response, and watchdog timing) is ensured across the full 1.2V–5.5V supply range per the Absolute Maximum Ratings and Electrical Characteristics tables.