Analog Devices Inc./Maxim Integrated MAX6865UK39D5S+T

Overview

The MAX6865UK39D5S+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%), 300ms minimum reset timeout, and integrated watchdog timer with 3.3s typical timeout. It monitors VCC, responds to manual reset (MR), and asserts active-low push-pull RESET during brownout, power-up, or watchdog expiration - used in battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK39D5S+T datasheet, MAX6865UK39D5S+T pinout, MAX6865UK39D5S+T application, or MAX6865UK39D5S+T equivalent, key selection criteria include guaranteed RESET validity down to VCC = +1.1V, immunity to sub-40µs VCC transients, MR glitch rejection of 200ns, and compatibility with 1.2V–5.5V supply rails.

Technical Context

This device integrates three core functions: precision voltage monitoring with hysteresis (0.5% of VTH), a manual reset input with internal 10kΩ pullup and 1µs minimum pulse width, and a watchdog timer that clears on any WDI edge and expires if WDI remains static beyond 3.3s (typ). The reset assertion persists for ≥300ms after VCC rises above 3.9V and MR deasserts.

It operates across –40°C to +85°C, draws only 170nA at 1.8V/25°C, and guarantees functional reset output down to VCC = 1.1V. Its push-pull active-low RESET delivers VOL ≤ 0.3V at ISINK = 1.2mA (VCC ≥ 2.12V) and VOH ≥ 0.8×VCC at ISOURCE = 500µA - enabling direct interface with 1.8V/2.5V/3.3V µP reset inputs without external level-shifting.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, 2.9mm × 1.6mm × 1.1mm, lead-free (RoHS-compliant), thermal pad not present.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6865UK39D5S+T, MAX6361KA29D3+T saves current but sacrifices system-level fault coverage, while TPS3808G33DBVR offers watchdog functionality at higher power and incompatible pinout/threshold - making MAX6865UK39D5S+T the optimal balance of nanopower operation, precise 3.9V monitoring, and full supervision features in SOT23-5.

Availability

MAX6865UK39D5S+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered industrial scanners, and smart wearables requiring stable component supply with guaranteed long-term availability and RoHS-compliant packaging.

Supply support for MAX6865UK39D5S+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 connectivity in demanding industrial, medical, and automotive applications.

The MAX6865UK39D5S+T belongs to the MAX68xx nanopower supervisory family, engineered specifically for ultra-low-power, safety-critical portable electronics where extended battery life and deterministic reset behavior are mandatory.

FAQ

What is the exact reset threshold voltage of the MAX6865UK39D5S+T?

The MAX6865UK39D5S+T has a factory-trimmed reset threshold of 3.900V with ±2.5% tolerance (3.802V to 3.998V) across –40°C to +85°C, as defined by the "39" suffix per Table 2 in the datasheet. This threshold is optimized for monitoring 3.3V rails with sufficient margin against ripple-induced false resets.

Does the MAX6865UK39D5S+T require external components for basic operation?

No, the MAX6865UK39D5S+T requires no external components for core functionality: it includes an internal 10kΩ pullup on MR, precision voltage reference, watchdog oscillator, and push-pull RESET driver. Only a 0.1µF ceramic bypass capacitor on VCC is recommended for noise immunity - no resistors, capacitors, or crystals are needed.

How does the watchdog timer in the MAX6865UK39D5S+T respond to software faults?

The MAX6865UK39D5S+T watchdog timer expires if the WDI pin remains static (high or low) for longer than 3.3s (typ), triggering a reset pulse lasting ≥300ms. The timer clears on every rising or falling edge at WDI - so firmware must toggle WDI at least once per 3.3s to prevent reset, ensuring detection of infinite loops or stalled execution.

Can the MAX6865UK39D5S+T operate reliably during deep battery discharge?

Yes, the MAX6865UK39D5S+T guarantees functional RESET output down to VCC = +1.1V, verified across temperature. Its 170nA supply current and operation from 1.2V–5.5V allow continuous supervision even as a single Li-ion cell discharges from 4.2V to 2.8V or alkaline cells fall to end-of-life voltages.

What is the MR input's minimum pulse width and glitch rejection capability for the MAX6865UK39D5S+T?

The MR input of the MAX6865UK39D5S+T requires a minimum pulse width of 1µs to assert reset and rejects glitches ≤200ns in duration. Its internal 10kΩ pullup ensures robustness against floating inputs, and it accepts standard CMOS logic levels - enabling direct connection to microcontroller GPIO or momentary switches without external debounce circuitry.