Analog Devices Inc./Maxim Integrated MAX6865UK40D2S+T

Overview

The MAX6865UK40D2S+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 4.000V reset threshold (±2.5%), 40ms minimum reset timeout, and integrated watchdog timer with 3.3s typical timeout. It monitors VCC, responds to manual reset (MR) assertion, and triggers reset on watchdog expiration - designed for reliable power-up/brownout protection in battery-critical systems.

For engineers reviewing the MAX6865UK40D2S+T datasheet, MAX6865UK40D2S+T pinout, MAX6865UK40D2S+T application, or MAX6865UK40D2S+T equivalent, this device delivers validated reset timing, guaranteed operation down to VCC = +1.1V, immunity to short VCC transients (<40µs at 100mV overdrive), and direct compatibility with CMOS-level MR/WDI inputs - critical for portable medical and low-power embedded designs.

Technical Context

This device integrates three core functions: precision voltage monitoring with hysteresis (0.5% of VTH), a monostable reset timeout generator (40ms min), and a watchdog timer that clears on any WDI edge and expires if WDI remains static >3.3s (typ). Its BiCMOS process enables stable operation across -40°C to +85°C with no external components required.

The MAX6865UK40D2S+T uses an active-low push-pull RESET output referenced to VCC, asserts reset when VCC falls below 4.000V, MR is pulled low, or WDI stalls, and holds reset asserted for ≥40ms after recovery - ensuring µP initialization completes before release. Reset validity is guaranteed down to VCC = +1.1V.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount. Compact 2.9mm × 1.6mm footprint with 0.95mm height - optimized for space-constrained portable PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6865UK40D2S+T, MAX6326UR29+T omits watchdog capability and offers different threshold/timing, while TPS3836K33DBVR provides no watchdog and draws ~15× more current - making MAX6865UK40D2S+T the sole option meeting simultaneous 4.0V threshold, 40ms timeout, and 3.3s watchdog in nanopower SOT23.

Availability

MAX6865UK40D2S+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, MP3 players, and smart pagers requiring stable component supply with long-term lifecycle support and lead-free compliance.

Supply support for MAX6865UK40D2S+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 management, sensing, and interface applications - emphasizing reliability, low power, and integration for demanding industrial and medical systems.

The MAX6865UK40D2S+T belongs to the MAX68xx nanopower supervisory family, engineered specifically for battery-powered portable electronics where extended runtime, deterministic reset behavior, and watchdog-assisted firmware integrity are mandatory.

FAQ

What is the exact reset threshold voltage of the MAX6865UK40D2S+T?

The MAX6865UK40D2S+T has a factory-trimmed reset threshold voltage of 4.000V, with tolerance of ±2.5% over the full operating temperature range (-40°C to +85°C). This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "40" corresponds to 4.000V nominal. The device guarantees reset assertion when VCC falls below this threshold and reset deassertion only after VCC exceeds it plus hysteresis (0.5% of VTH).

Does the MAX6865UK40D2S+T include a watchdog timer, and what is its timeout?

Yes, the MAX6865UK40D2S+T includes a watchdog timer with a typical timeout of 3.3 seconds, indicated by the "S" suffix in the part number. The watchdog clears on any rising or falling edge at the WDI pin and expires only if WDI remains static (high or low) beyond this period. This behavior is explicitly defined in Table 3 (Watchdog Timeout) and applies to all MAX6864–MAX6869 variants with "S" suffix.

What is the reset timeout period for the MAX6865UK40D2S+T, and is it adjustable?

The MAX6865UK40D2S+T has a fixed minimum reset timeout period of 40ms, denoted by the "D2" suffix. This value is non-adjustable and is one of six factory-set options (D1–D6) ranging from 10ms to 1200ms. Unlike MAX6861–MAX6863, the MAX6865UK40D2S+T does not feature a CT pin for dynamic timeout selection - the D2 setting is permanently configured during manufacturing.

What type of reset output does the MAX6865UK40D2S+T provide?

The MAX6865UK40D2S+T provides an active-low push-pull RESET output (Pin 1), as confirmed in the MAX6864/MAX6865/MAX6866 Pin Description section. This means the output actively drives low during reset and high-impedance (not actively high) when deasserted - eliminating the need for an external pullup resistor and ensuring clean, rail-referenced logic levels compatible with standard µP reset inputs.

Is the MAX6865UK40D2S+T compatible with 1.8V or 2.5V supply rails?

Yes, the MAX6865UK40D2S+T operates across a VCC range of 1.2V to 5.5V and guarantees valid reset output down to VCC = +1.1V. Its 4.000V reset threshold is intended for monitoring higher rails (e.g., 3.3V or 5V), but the device itself can be powered from 1.8V or 2.5V supplies - provided the monitored VCC rail meets the threshold requirement. Electrical characteristics (e.g., ICC = 170nA typ) are specified at VCC = 2.5V, confirming robust operation at that level.