Analog Devices Inc./Maxim Integrated MAX6866UK29D3S+

Overview

The MAX6866UK29D3S+ from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, a factory-trimmed 2.925V reset threshold (suffix "29"), 300ms minimum reset timeout (suffix "D3"), and integrated watchdog timer with 3.3s typical timeout (suffix "S"). It monitors VCC, responds to manual reset (MR), and triggers reset on watchdog expiration - designed for battery-powered medical and portable electronics requiring guaranteed reset validity down to VCC = +1.1V.

For engineers reviewing the MAX6866UK29D3S+ datasheet, MAX6866UK29D3S+ pinout, MAX6866UK29D3S+ application, or MAX6866UK29D3S+ equivalent, key selection criteria include its open-drain active-low RESET output, watchdog input (WDI) compatibility with µP firmware toggling, immunity to short VCC transients (<40µs at 100mV overdrive), and operation across –40°C to +85°C.

Technical Context

The MAX6866UK29D3S+ integrates three core functions: precision voltage monitoring with ±2.5% threshold accuracy over temperature, a manual reset input (MR) with 250ns delay and internal 10kΩ pullup, and a watchdog timer that clears on any WDI edge and expires if WDI remains static beyond 3.3s (typ). Its reset assertion logic combines VCC undervoltage, MR low, or WDI timeout - all forcing open-drain RESET low for ≥300ms after recovery.

It uses BiCMOS process technology (2848 transistors) to achieve nanoscale quiescent current while maintaining guaranteed reset validity down to VCC = +1.1V and robust noise immunity - including 200ns MR glitch rejection and transient immunity validated via normalized VTH vs. temperature curves and max transient duration vs. overdrive graphs.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount, 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 MAX6864UK29D3S+, the MAX6866UK29D3S+ enables voltage-level flexibility via open-drain RESET; compared with TPS3836K29DBVR, it delivers 7× lower ICC and integrated watchdog - critical for long-life, safety-critical portable medical designs.

Availability

MAX6866UK29D3S+ is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, MP3 players, and legacy cell phone modules requiring stable component supply, extended battery life, and fail-safe reset supervision.

Supply support for MAX6866UK29D3S+ 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 MAX6854–MAX6869 family was designed specifically for ultra-low-power microprocessor supervision in battery-critical portable equipment - delivering nanoscale ICC, precise voltage thresholds, and integrated watchdog functionality in minimal 5-pin SOT23 packages.

FAQ

What is the exact reset threshold voltage of the MAX6866UK29D3S+?

The MAX6866UK29D3S+ has a factory-trimmed reset threshold of 2.925V, with ±2.5% tolerance over –40°C to +85°C. This value is confirmed by the "29" suffix in the part number per Maxim's Threshold Suffix Guide (Table 2), and is validated in the Electrical Characteristics table where VTH = 2.925V (typ) under MIN/TYP/MAX columns. The MAX6866UK29D3S+ maintains this accuracy without external calibration.

Does the MAX6866UK29D3S+ require an external pullup resistor on the RESET pin?

Yes, the MAX6866UK29D3S+ features an open-drain active-low RESET output (Pin 1), which requires an external pullup resistor to a valid logic rail (e.g., µP I/O voltage). The datasheet specifies this explicitly in the Pin Description and Applications Information sections. Without the pullup, RESET cannot drive high, rendering the supervisory function nonfunctional. Typical values range from 10kΩ to 100kΩ depending on bus capacitance and rise-time requirements.

What is the watchdog timeout behavior of the MAX6866UK29D3S+?

The MAX6866UK29D3S+ implements a watchdog timer with a typical timeout of 3.3s (S suffix), with min/max of 1.5s/7.75s. The timer clears on any rising or falling edge at WDI (Pin 4) and expires only if WDI remains static (high or low) beyond the timeout period. Upon expiration, it asserts RESET low for the full 300ms reset timeout (D3), independent of VCC or MR status - ensuring recovery from complete firmware lockup.

Can the MAX6866UK29D3S+ operate reliably below 1.8V?

Yes, the MAX6866UK29D3S+ operates from VCC = 1.2V to 5.5V and guarantees valid reset assertion down to VCC = +1.1V. Its 170nA typical supply current at 1.8V and functional specification down to 1.2V make it suitable for single-cell Li-ion (2.7V–4.2V) and coin-cell (2.0V–3.0V) applications. The Electrical Characteristics table confirms ICC = 170nA (typ) at VCC = 1.8V and VTH = 2.925V remains valid across the full 1.2V–5.5V range.

Is the MAX6866UK29D3S+ pin-compatible with other devices in the MAX68xx family?

The MAX6866UK29D3S+ shares the identical 5-pin SOT23-5 pinout with all MAX6864–MAX6869 variants (e.g., MAX6864, MAX6865, MAX6867), as confirmed in the Pin Configurations diagram and Selector Guide. Pin 1 = RESET, Pin 2 = GND, Pin 3 = MR, Pin 4 = WDI, Pin 5 = VCC. This allows direct substitution within the MAX6864–MAX6869 series when reset threshold, timeout, and watchdog options match - though output type (open-drain vs. push-pull) must be verified.