Analog Devices Inc./Maxim Integrated MAX6856UK31D3+T

Overview

The MAX6856UK31D3+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring active-low open-drain reset output, manual reset input (MR), and factory-trimmed 3.075V reset threshold (suffix "31"). It provides 150ms minimum reset timeout (suffix "D3"), ultra-low 170nA typical supply current, and guaranteed reset validity down to VCC = +1.1V. It is used in battery-powered medical devices such as glucose monitors to ensure reliable power-on reset and brownout protection.

For engineers reviewing the MAX6856UK31D3+T datasheet, MAX6856UK31D3+T pinout, MAX6856UK31D3+T application, or MAX6856UK31D3+T equivalent, key selection criteria include its open-drain RESET output compatibility with mixed-voltage systems, immunity to short VCC transients (<40µs at 100mV overdrive), and absence of external components required for basic operation.

Technical Context

This device integrates voltage monitoring, manual reset assertion, and reset timing logic - but no watchdog timer (MAX6856 excludes WDI functionality per Selector Guide). Its internal comparator continuously monitors VCC against a precision bandgap-derived threshold, triggering reset when VCC falls below 3.075V ±2.5%, with hysteresis of 0.5% of VTH to prevent chatter near threshold.

The reset output remains asserted for ≥150ms after VCC rises above threshold and MR deasserts, ensuring µP initialization completes. The open-drain RESET requires an external pullup; its leakage is ≤25nA when deasserted, supporting high-impedance interfacing across voltage domains (0–5.5V).

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount, 2.9mm × 1.6mm footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3836K33DBVR and STM6315RWX6F, the MAX6856UK31D3+T uniquely combines ultra-low 170nA ICC, MR input, open-drain flexibility, and 150ms timeout - making it optimal for space-constrained, long-life, user-serviceable portable medical electronics.

Availability

MAX6856UK31D3+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, MP3 players, and PDAs requiring stable component supply with guaranteed long-term availability and lead-free compliance.

Supply support for MAX6856UK31D3+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 resource-constrained systems.

The MAX6854–MAX6869 family was engineered specifically for nanopower supervision in battery-critical portable electronics, emphasizing sub-µA ICC, small SOT23 packaging, and robust reset timing without external components.

FAQ

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

The MAX6856UK31D3+T has a factory-trimmed reset threshold of 3.075V, with tolerance of ±2.5% over temperature (−40°C to +85°C). This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "31" corresponds to VTH = 3.075V. The MAX6856UK31D3+T maintains this accuracy with 0.5% hysteresis to prevent oscillation near the trip point.

Does the MAX6856UK31D3+T include a watchdog timer function?

No, the MAX6856UK31D3+T does not include a watchdog timer. Per the Selector Guide and Pin Description sections, only MAX6864–MAX6869 variants feature WDI input; MAX6856 belongs to the MR-only subgroup (no WDI pin, no watchdog circuitry). The MAX6856UK31D3+T provides voltage monitoring, manual reset, and fixed reset timeout - but no watchdog functionality.

What does the "D3" suffix in MAX6856UK31D3+T indicate?

The "D3" suffix in MAX6856UK31D3+T specifies the reset timeout period: D3 corresponds to a minimum timeout of 150ms, with typical 225ms and maximum 300ms (per Table 4, Reset Timeout Periods). This timeout begins after VCC rises above the 3.075V threshold and MR is deasserted, ensuring sufficient time for microprocessor initialization before release.

Can the MAX6856UK31D3+T drive a 3.3V microcontroller reset input directly?

Yes - the MAX6856UK31D3+T's open-drain RESET output can interface directly with a 3.3V µP reset input when pulled up to 3.3V. Its leakage current is ≤25nA when deasserted, and it sinks up to 1.2mA when asserted (at VCC ≥2.12V), meeting standard µP reset input requirements. No level shifter is needed, and the external pullup resistor value is selected based on rise-time and bus capacitance.

Is the MAX6856UK31D3+T pin-compatible with other devices in the MAX68xx family?

The MAX6856UK31D3+T shares the same 5-pin SOT23-5 pinout as MAX6854, MAX6855, MAX6858, and MAX6860–MAX6869, but functional pin assignments differ. Specifically, MAX6856 uses Pins 1 (RESET), 2 (GND), 3 (MR), 4 (GND), and 5 (VCC) - identical to MAX6854/MAX6855. However, it is not pin-compatible with MAX6864 (which substitutes Pin 1 for WDI) or MAX6861 (which uses Pin 1 for CT). Always verify pin function per device variant.