Analog Devices Inc./Maxim Integrated MAX6865UK21D4S+T

Overview

The MAX6865UK21D4S+T 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 2.100V reset threshold (±2.5%), 1200ms minimum reset timeout, manual reset input (MR), and watchdog timer with 3.3s typical timeout. It monitors VCC in battery-powered medical and portable electronics to ensure reliable µP initialization during power-up, brownout, or software lockup.

For engineers reviewing the MAX6865UK21D4S+T datasheet, MAX6865UK21D4S+T pinout, MAX6865UK21D4S+T application, or MAX6865UK21D4S+T equivalent, this page delivers verified functional identity, exact pin roles, confirmed timing parameters, real-world use context, and validated alternative options for low-power system supervision.

Technical Context

This device integrates three core supervision functions: precise VCC voltage monitoring with hysteresis (0.5% of VTH), a glitch-immune manual reset input with 1µs minimum pulse width and 200ns noise rejection, and a watchdog timer that triggers reset if WDI remains static beyond 3.3s (typ). All logic thresholds scale with VCC (e.g., MR VIH = 0.7×VCC).

The internal reset timeout generator guarantees minimum assertion duration after VCC recovery or MR release, independent of temperature (±1% variation over –40°C to +85°C). Reset output remains valid down to VCC = 1.1V, and the open-drain or push-pull configuration supports direct interfacing with diverse µP reset inputs.

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 supervision applications.

Compared with MAX6865UK21D4S+T, MAX6864UK21D4S+T removes CT functionality but retains identical supervision timing and watchdog capability, while TPS3836K21DBVR trades nanopower operation and watchdog for broader vendor support and simpler qualification - making it viable only in non-battery-critical designs.

Availability

MAX6865UK21D4S+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, wearable trackers, and industrial handheld scanners requiring stable component supply with long-term lifecycle assurance.

Supply support for MAX6865UK21D4S+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 MAX6854–MAX6869 family delivers nanopower supervision for battery-constrained systems, emphasizing ultra-low ICC, wide VCC range, and integrated watchdog functionality to replace discrete reset + timer solutions.

FAQ

What is the exact reset threshold voltage of the MAX6865UK21D4S+T?

The MAX6865UK21D4S+T has a factory-trimmed reset threshold voltage of 2.100V, with ±2.5% tolerance over temperature (–40°C to +85°C). This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "21" corresponds to 2.100V nominal. The MAX6865UK21D4S+T maintains this specification without external calibration.

Does the MAX6865UK21D4S+T include a watchdog timer, and what is its timeout?

Yes, the MAX6865UK21D4S+T includes a watchdog timer with a typical timeout of 3.3 seconds, denoted by the "S" suffix in the part number. This is verified in Table 3 (Watchdog Timeout) and the Ordering Information section, which specifies "S" as 1.5s/3.3s/7.75s (min/typ/max). The timer resets on any WDI edge and triggers reset if WDI remains static beyond this period.

What does the "D4" in MAX6865UK21D4S+T indicate?

The "D4" in MAX6865UK21D4S+T specifies the reset timeout period option: 1200ms minimum (1800ms typical, 2400ms maximum), per Table 4 (Reset Timeout Periods). This ensures the reset signal remains asserted long enough for full µP initialization, especially in systems with slow clock startup or complex bootloader sequences.

Is the MAX6865UK21D4S+T pin-compatible with other devices in the MAX68xx family?

The MAX6865UK21D4S+T uses the standard 5-pin SOT23-5 package and shares identical pinout with MAX6864/MAX6866/MAX6867–MAX6869 variants: Pin 1 = RESET, Pin 2 = GND, Pin 3 = MR, Pin 4 = WDI, Pin 5 = VCC. This allows drop-in replacement among watchdog-enabled members without PCB changes.

What is the supply current of the MAX6865UK21D4S+T at 1.8V and 25°C?

The MAX6865UK21D4S+T draws 170nA typical supply current at VCC = 1.8V and TA = +25°C, as specified in the Electrical Characteristics table under "Supply Current (ICC)" with condition "VCC = 1.8V". This ultra-low value is central to its nanopower classification and enables decade-long operation on primary lithium cells.