Analog Devices Inc./Maxim Integrated MAX6865UK21D3L+T

Overview

The MAX6865UK21D3L+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, combining voltage monitoring, manual reset input (MR), and watchdog timer (WDI) with factory-trimmed 2.100V reset threshold, 150ms minimum reset timeout, and 209s typical watchdog timeout. It asserts an active-high push-pull RESET output during VCC brownout, MR assertion, or watchdog expiration, and guarantees valid reset operation down to VCC = +1.1V - ideal for battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK21D3L+T datasheet, MAX6865UK21D3L+T pinout, MAX6865UK21D3L+T application, or MAX6865UK21D3L+T equivalent, key selection criteria include its ultra-low 170nA typical supply current, 209s watchdog timeout option (L suffix), pin-selectable reset delay compatibility, immunity to short VCC transients, and guaranteed reset validity at low supply voltages.

Technical Context

The MAX6865UK21D3L+T implements a dual-monitoring architecture: a precision bandgap-based voltage detector triggers reset when VCC falls below 2.100V ±2.5%, while a monostable watchdog timer clears on any WDI edge and expires if no transition occurs within 209s (typ). Its internal 10kΩ MR pullup and glitch rejection (200ns) enable robust manual reset without external components.

This device uses BiCMOS process technology (2848 transistors) and operates across –40°C to +85°C. The active-high push-pull RESET output sources up to 500µA at VCC ≥ 2.38V (VOH ≥ 0.8×VCC), and sinks <0.3V at ISINK = 1.2mA - ensuring reliable µP reset signaling even under load.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5 (lead-free, +T 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 MAX6864UK21D3L+T and TPS3837K21DBVR, the MAX6865UK21D3L+T uniquely delivers active-high reset signaling, ultra-low 170nA current, and integrated watchdog - making it optimal for next-generation portable medical electronics where power, safety, and pin compatibility are co-constrained.

Availability

MAX6865UK21D3L+T is available at Aetrix Electronics and suitable for glucose monitors, patient vital sign loggers, handheld diagnostic scanners, and wearable drug infusion pumps requiring stable component supply across industrial temperature ranges and long product lifecycles.

Supply support for MAX6865UK21D3L+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, mixed-signal, and power management ICs for demanding industrial, medical, and communications applications.

The MAX6865UK21D3L+T belongs to Maxim's nanopower µP supervisory family, engineered specifically for battery-critical portable medical and IoT endpoints where ultra-low ICC, guaranteed low-voltage reset, and watchdog reliability are non-negotiable.

FAQ

What is the exact reset threshold voltage of the MAX6865UK21D3L+T?

The MAX6865UK21D3L+T has a factory-trimmed reset threshold of 2.100V 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 "21" corresponds to 2.100V nominal. The device asserts RESET when VCC falls below this threshold and holds it asserted for 150ms (min) after VCC recovers.

Does the MAX6865UK21D3L+T support active-high or active-low reset output?

The MAX6865UK21D3L+T features an active-high push-pull RESET output, as specified in its pin description and Selector Guide. Pin 1 drives high during reset conditions (VCC brownout, MR assertion, or WDI timeout) and returns low after the 150ms timeout expires. This eliminates the need for an external pullup resistor and directly matches µPs with active-high reset inputs.

What does the "L" suffix in MAX6865UK21D3L+T indicate?

The "L" suffix in MAX6865UK21D3L+T denotes the watchdog timeout period option: 209s typical (95s min, 487s max), per Table 3 (Watchdog Timeout). This distinguishes it from the "S" option (3.3s typical). The L-suffix enables longer software execution windows between watchdog refreshes - critical for low-duty-cycle portable medical devices.

How is the reset timeout period configured on the MAX6865UK21D3L+T?

The MAX6865UK21D3L+T has a fixed 150ms minimum reset timeout period, indicated by the "D3" suffix in its part number. Unlike the MAX6861–MAX6863 series, it does not feature a CT pin for dynamic timeout selection. The D3 option is one of six factory-set timeout values (10ms to 1200ms), and this value is permanently programmed during manufacturing.

Can the MAX6865UK21D3L+T operate reliably at VCC = 1.2V?

Yes - the MAX6865UK21D3L+T guarantees valid RESET assertion down to VCC = +1.1V, as stated in the Electrical Characteristics table. At VCC = 1.2V, it fully meets all specifications including 170nA supply current (typ), 2.100V threshold accuracy, and proper MR/WDI input thresholds. This ensures fail-safe behavior during deep brownout conditions common in aging batteries.