Analog Devices Inc./Maxim Integrated MAX6856UK31D3+

Overview

The MAX6856UK31D3+ from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, providing voltage monitoring, manual reset input (MR), and fixed 150ms minimum reset timeout. It asserts an active-low open-drain RESET output when VCC drops below its factory-trimmed 3.075V threshold (suffix "31"), during MR assertion, or after power-up/brownout - ensuring reliable µP initialization in battery-powered medical and portable systems.

For engineers reviewing the MAX6856UK31D3+ datasheet, MAX6856UK31D3+ pinout, MAX6856UK31D3+ application, or MAX6856UK31D3+ equivalent, key selection criteria include its 170nA typical supply current, guaranteed RESET validity down to VCC = +1.1V, immunity to short VCC transients (<40µs at 100mV overdrive), and compatibility with 1.2V–5.5V supply rails in space-constrained designs.

Technical Context

This device integrates a precision voltage monitor with ±2.5% threshold accuracy, a fixed-reset-timeout generator (D3 = 150ms min), and a CMOS-compatible manual reset input with 10kΩ internal pullup and 250ns MR-to-RESET delay. Its open-drain RESET output requires an external pullup and supports logic-level translation across supply domains up to 5.5V.

The MAX6856UK31D3+ lacks watchdog timer (WDI) and CT (timeout select) pins - distinguishing it from MAX6864–MAX6869 and MAX6861–MAX6863 variants. It operates across –40°C to +85°C and guarantees functional reset assertion even as VCC falls to 1.1V, enabling robust brownout protection in ultra-low-power systems.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, surface-mount, lead-free (indicated by '+' suffix), 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 TPS3838K33DBVR and MAX6361KA33+T, the MAX6856UK31D3+ delivers 7× lower supply current and integrated MR support - critical for battery longevity and field-serviceable reset in medical and portable equipment, despite requiring external pullup for its open-drain output.

Availability

MAX6856UK31D3+ is available at Aetrix Electronics and suitable for portable medical devices, battery-powered IoT sensors, and industrial handheld terminals requiring stable component supply with guaranteed long-term availability and full traceability.

Supply support for MAX6856UK31D3+ 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, medical, and communications applications.

The MAX685x family was designed specifically for ultra-low-power microprocessor supervision in space- and energy-constrained portable electronics - emphasizing nanoscale current consumption, precision voltage thresholds, and minimal external component count.

FAQ

What is the exact reset threshold voltage of the MAX6856UK31D3+?

The MAX6856UK31D3+ has a factory-trimmed reset threshold of 3.075V, with guaranteed limits of 2.998V (min) and 3.152V (max) over –40°C to +85°C. This corresponds to the "31" suffix in the part number per Maxim's Threshold Suffix Guide (Table 2), making it optimized for supervision of nominal 3.3V rails with ±2.5% accuracy.

Does the MAX6856UK31D3+ include a watchdog timer function?

No, the MAX6856UK31D3+ does not include a watchdog timer. It belongs to the MAX6854/MAX6855/MAX6856 subgroup, which provides only voltage monitoring and manual reset (MR) functionality. Watchdog capability is exclusive to MAX6864–MAX6869 variants, identifiable by "S" or "L" suffixes in the ordering code.

What is the purpose of the dual GND pins (Pins 2 and 4) on the MAX6856UK31D3+?

Pins 2 and 4 on the MAX6856UK31D3+ are both connected to the internal ground net. This dual-GND configuration improves thermal dissipation and reduces ground impedance in high-noise environments. It also enhances immunity to PCB-level noise coupling - especially beneficial in compact, battery-powered layouts where ground return paths are constricted.

Can the MAX6856UK31D3+ drive a 5V microcontroller reset input?

Yes, the MAX6856UK31D3+ features an open-drain active-low RESET output (Pin 1), which can interface directly with 5V µP reset inputs by using an external pullup resistor to the 5V rail. The output is rated for up to 5.5V, and leakage current remains below 25nA when deasserted - ensuring clean logic-level translation without additional level-shifters.

Is the MR input of the MAX6856UK31D3+ compatible with direct connection to a microcontroller GPIO?

Yes, the MR input (Pin 3) is fully compatible with standard CMOS GPIO outputs. It features an internal 10kΩ pullup to VCC and accepts logic-low signals down to 0.3×VCC. A µP GPIO configured as open-drain or push-pull can assert MR directly; no series resistor or external pullup is required unless driving over long traces (>10cm) in noisy environments.