Analog Devices Inc./Maxim Integrated MAX6865UK39D1L+T

Overview

The MAX6865UK39D1L+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 3.9V reset threshold (±2.5%), 10ms minimum reset timeout, and integrated watchdog timer with 209s typical timeout. It monitors VCC, responds to manual reset (MR), and asserts active-high push-pull RESET during brownout, power-up, or watchdog expiration - used in battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK39D1L+T datasheet, MAX6865UK39D1L+T pinout, MAX6865UK39D1L+T application, or MAX6865UK39D1L+T equivalent, key selection criteria include its 3.9V reset threshold accuracy, 209s watchdog timeout option, 10ms reset delay, guaranteed RESET validity down to VCC = +1.1V, and immunity to sub-40µs VCC transients at 100mV overdrive.

Technical Context

This device integrates three core functions: precision voltage monitoring with hysteresis (0.5% of VTH), a manual reset input with 250ns MR-to-reset delay and internal 10kΩ pullup, and a watchdog timer that clears on any WDI edge and expires if WDI remains static beyond 209s (typ). The watchdog operates independently of VCC level as long as VCC ≥ 1.1V.

The reset logic combines VCC monitoring, MR assertion, and watchdog expiration using OR logic - any one condition triggers RESET assertion. After deassertion, the internal timer enforces a fixed 10ms minimum timeout before RESET deasserts, ensuring reliable µP initialization even under noisy supply conditions.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount. Pin 1 is RESET (active-high push-pull), Pin 2 is GND, Pin 3 is MR (active-low manual reset), Pin 4 is WDI (watchdog input), Pin 5 is VCC (supply monitor input).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK39D1L+T, the MAX6865UK39D1L+T avoids external inversion circuitry for active-high reset interfaces; versus TPS3837K33DBVR, it delivers 10× lower ICC and critical watchdog supervision for safety-critical portable medical use cases.

Availability

MAX6865UK39D1L+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered instrumentation, and industrial handheld equipment requiring stable component supply across extended product lifecycles.

Supply support for MAX6865UK39D1L+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 MAX6865UK39D1L+T belongs to the MAX68xx nanopower supervisory family, engineered specifically for ultra-low-power, safety-critical portable electronics where long battery life and robust fault detection are mandatory.

FAQ

What is the exact reset threshold voltage of the MAX6865UK39D1L+T?

The MAX6865UK39D1L+T has a factory-trimmed reset threshold of 3.900V with ±2.5% tolerance over temperature and voltage. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "39" corresponds to VTH = 3.900V (min 3.802V, typ 3.900V, max 3.998V). The MAX6865UK39D1L+T uses this precise threshold to supervise 3.3V/3.6V system rails without external resistive dividers.

Does the MAX6865UK39D1L+T support active-high or active-low reset output?

The MAX6865UK39D1L+T features an active-high push-pull RESET output, as confirmed in the MAX6865 pin description (Page 8) and Selector Guide (Page 16). When a fault occurs - VCC drops below 3.9V, MR is pulled low, or WDI times out - RESET drives high. It remains high for the full 10ms reset timeout period before returning low. This eliminates the need for external pullup resistors required by open-drain variants.

What is the watchdog timeout period for the MAX6865UK39D1L+T?

The MAX6865UK39D1L+T implements a 209s typical watchdog timeout period, denoted by the "L" suffix in its part number. Per Table 3 (Watchdog Timeout), "L" specifies min 95s, typ 209s, max 487s. The timer resets on any rising or falling edge at WDI and expires only if WDI remains static beyond this interval - enabling supervision of long-duration firmware routines in portable medical devices.

Can the MAX6865UK39D1L+T operate reliably at low VCC levels?

Yes, the MAX6865UK39D1L+T guarantees valid RESET output down to VCC = +1.1V, as specified in the Electrical Characteristics table (Page 2). This ensures supervision remains active during deep brownout conditions common in battery-powered systems nearing end-of-life. Below 1.1V, RESET behavior is not guaranteed, but most target µPs cease operation above this threshold.

Is the MAX6865UK39D1L+T pin-compatible with other MAX68xx devices?

The MAX6865UK39D1L+T uses the standard 5-pin SOT23-5 package and shares identical pinout with MAX6864/MAX6866/MAX6867–MAX6869 (Pin 1: RESET, Pin 2: GND, Pin 3: MR, Pin 4: WDI, Pin 5: VCC). However, it is not pin-compatible with MAX6861–MAX6863 (which use CT instead of WDI) or MAX6854–MAX6856 (which lack WDI). Always verify function mapping before substitution.