Analog Devices Inc./Maxim Integrated MAX6866UK20D3S+T

Overview

The MAX6866UK20D3S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 2.0V reset threshold (±2.5%), 300ms minimum reset timeout, and integrated watchdog timer with 3.3s typical timeout. It monitors VCC, responds to manual reset (MR), and asserts open-drain active-low RESET during brownout, power-up, or watchdog expiration - used in battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6866UK20D3S+T datasheet, MAX6866UK20D3S+T pinout, MAX6866UK20D3S+T application, or MAX6866UK20D3S+T equivalent, this page delivers verified specifications, validated pin functions, confirmed timing behavior under VCC transients down to 1.1V, and real-world alternative selection guidance for low-power embedded reset supervision.

Technical Context

The MAX6866UK20D3S+T implements a precision bandgap-based voltage monitor with 0.5% hysteresis, a digital watchdog timer that clears on any WDI edge (min pulse width 150ns), and a fixed 300ms reset timeout after VCC recovery or MR deassertion. Its internal 10kΩ MR pullup and guaranteed RESET validity down to VCC = +1.1V enable robust operation in deep-brownout conditions.

This device belongs to the MAX6864–MAX6869 series with S-suffix watchdog (3.3s typ), D3 reset timeout (150–300ms), and 20-suffix threshold (2.000V). Unlike MAX6861–MAX6863, it lacks CT pin selectability; unlike MAX6854–MAX6856, it includes WDI but no CT, and provides only open-drain active-low RESET output.

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 MAX6866UK20D3S+T, MAX6864UK20D3S+T offers identical supervision timing but different output drive architecture, while TPS3836K20DBVR trades off watchdog capability and nanopower operation for lower unit cost in static reset-only designs.

Availability

MAX6866UK20D3S+T is available at Aetrix Electronics and suitable for portable medical devices, wireless sensor nodes, low-power wearables, and energy-harvesting systems requiring stable component supply with guaranteed long-term availability.

Supply support for MAX6866UK20D3S+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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power-management ICs for industrial, medical, and communications applications.

The MAX6864–MAX6869 family was designed specifically for ultra-low-power microprocessor supervision in battery-critical portable electronics, integrating precision voltage monitoring, manual reset, and watchdog functionality in minimal 5-pin SOT23 packaging.

FAQ

What is the exact reset threshold voltage of the MAX6866UK20D3S+T?

The MAX6866UK20D3S+T has a factory-trimmed reset threshold of 2.000V with ±2.5% tolerance over -40°C to +85°C. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "20" corresponds to VTH = 2.000V. The MAX6866UK20D3S+T maintains this accuracy across temperature, with normalized VTH variation <±0.5% from -40°C to +85°C per typical characteristics graph.

Does the MAX6866UK20D3S+T support open-drain reset output?

Yes, the MAX6866UK20D3S+T provides an open-drain active-low RESET output on Pin 1. As specified in the MAX6864/MAX6865/MAX6866 Pin Description section, this output requires an external pullup resistor to interface with downstream logic. The device guarantees VOL ≤0.3V when sinking 50µA at VCC ≥1.1V, enabling reliable interfacing across voltage domains - a key design feature of the MAX6866UK20D3S+T.

What is the watchdog timeout behavior of the MAX6866UK20D3S+T?

The MAX6866UK20D3S+T features a watchdog timer with S-suffix configuration, delivering 1.5s minimum, 3.3s typical, and 7.75s maximum timeout. It clears on any rising or falling edge at WDI (Pin 4), accepts pulses as short as 150ns, and remains disabled until first WDI transition after power-up. The MAX6866UK20D3S+T does not assert reset while the watchdog is timing out - only upon timeout expiration, triggering the full D3 reset period (150–300ms).

Can the MAX6866UK20D3S+T operate reliably below 1.8V?

Yes, the MAX6866UK20D3S+T operates from VCC = 1.2V to 5.5V and guarantees valid RESET assertion down to VCC = +1.1V. Electrical Characteristics confirm RESET remains functional at 1.2V minimum supply, and the "RESET Valid to VCC = +1.1V" feature is explicitly guaranteed across temperature. This makes the MAX6866UK20D3S+T suitable for single-cell lithium or NiMH systems where voltage drops below 1.8V during discharge.

Is there an internal pullup on the MR pin of the MAX6866UK20D3S+T?

Yes, the MAX6866UK20D3S+T includes an internal 10kΩ pullup resistor from MR (Pin 3) to VCC. This is documented in both the Pin Description table and Applications Information section, which states "MR is internally pulled up to VCC through 10kΩ." No external pullup is required; MR may be left unconnected or tied to VCC when unused. The MAX6866UK20D3S+T accepts standard CMOS logic levels and supports momentary switch-to-ground implementation without debounce circuitry.