Analog Devices Inc./Maxim Integrated MAX6865UK21D1S+T

Overview

The MAX6865UK21D1S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, combining voltage monitoring (reset threshold = +2.100V), manual reset input (MR), and watchdog timer (timeout = 3.3s typ) with ultra-low 170nA typical supply current. It asserts an active-low push-pull RESET output during VCC brownout, MR assertion, or watchdog timeout, and holds reset for 10ms minimum after recovery - ideal for battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK21D1S+T datasheet, MAX6865UK21D1S+T pinout, MAX6865UK21D1S+T application, or MAX6865UK21D1S+T equivalent, key selection criteria include its guaranteed reset validity down to VCC = +1.1V, immunity to ≤40µs VCC transients at 100mV overdrive, fixed 10ms reset timeout, and SOT23-5 footprint compatibility with TPS3836/TPS3837/TPS3838.

Technical Context

This device integrates a precision bandgap-based voltage monitor, a monostable watchdog timer triggered by WDI edge transitions, and a digital reset timeout generator. Its internal 10kΩ MR pullup, glitch-rejecting MR input (200ns rejection), and WDI pulse-width tolerance (≥150ns) enable robust operation in noisy portable environments without external components.

The reset logic combines three independent assertion sources - VCC falling below 2.100V ±2.5%, MR low, or WDI stall exceeding 3.3s - with synchronized deassertion after a fixed 10ms timeout. The push-pull RESET output delivers VOH ≥0.8×VCC (ISOURCE = 500µA) and VOL ≤0.3V (ISINK = 1.2mA) across 1.71V–5.5V VCC range.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, -40°C to +85°C operating range.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK21D1S+T, the MAX6865UK21D1S+T offers identical supervision parameters but adds CT pin flexibility (unused here); versus TPS3836K21DBVR, it delivers 10× lower ICC and integrated watchdog - essential for firmware safety-critical portable devices.

Availability

MAX6865UK21D1S+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, MP3 players, and cell phone accessories requiring stable component supply with long-term lifecycle support.

Supply support for MAX6865UK21D1S+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 timing applications, with focus on ultra-low-power and high-reliability solutions.

The MAX6854–MAX6869 family targets battery-powered portable electronics, delivering nanopower supervision with integrated watchdog and manual reset in minimal SOT23-5 footprint.

FAQ

What is the exact reset threshold voltage of the MAX6865UK21D1S+T?

The MAX6865UK21D1S+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) where suffix '21' corresponds to 2.100V nominal, and Electrical Characteristics specify VTH = VTH ±2.5%. The device guarantees valid reset operation down to VCC = +1.1V, making it suitable for deep brownout recovery scenarios in the MAX6865UK21D1S+T.

Does the MAX6865UK21D1S+T include a watchdog timer, and what is its timeout?

Yes, the MAX6865UK21D1S+T includes a watchdog timer with a typical timeout of 3.3 seconds, indicated by the 'S' suffix in the part number. Per Table 3 (Watchdog Timeout), 'S' denotes 1.5s (min), 3.3s (typ), and 7.75s (max). The timer resets on any WDI edge and triggers RESET if WDI remains static beyond this period. This behavior is fully documented in the MAX6865UK21D1S+T datasheet's Watchdog Input section and functional diagram.

What is the reset timeout period for the MAX6865UK21D1S+T, and is it configurable?

The MAX6865UK21D1S+T has a fixed reset timeout period of 10ms minimum, denoted by the 'D1' suffix. Table 4 confirms D1 = 10ms (min), 15ms (typ), 25ms (max). Unlike MAX6861–MAX6863 variants, the MAX6865UK21D1S+T does not support pin-selectable timeout - CT pin is absent, and timeout is factory-set. This fixed 10ms duration ensures rapid µP release after power stabilization in the MAX6865UK21D1S+T.

What package type and pin count does the MAX6865UK21D1S+T use?

The MAX6865UK21D1S+T uses a 5-pin SOT23-5 package, as specified in the Ordering Information table and Pin Configurations diagram. Pinout is: 1=RESET (active-low push-pull), 2=GND, 3=MR, 4=WDI, 5=VCC. This matches the MAX6864–MAX6866 series layout and is compatible with standard SOT23 footprints used for TPS3836/TPS3837/TPS3838. The '+T' suffix confirms lead-free RoHS-compliant packaging for the MAX6865UK21D1S+T.

How does the manual reset (MR) input function in the MAX6865UK21D1S+T?

The MR input of the MAX6865UK21D1S+T is an active-low signal with internal 10kΩ pullup to VCC. Driving MR low asserts RESET immediately, and RESET remains asserted for the full 10ms timeout after MR returns high. It accepts CMOS logic levels, rejects glitches <200ns, and requires only a momentary switch to GND - no external debounce needed. This MR behavior is identical across MAX6864–MAX6869 and explicitly defined for the MAX6865UK21D1S+T in the Pin Description and Applications Information sections.