Analog Devices Inc./Maxim Integrated MAX6865UK46D3S

Overview

MAX6865UK46D3S from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, combining voltage monitoring (4.625V factory-trimmed reset threshold), manual reset input (MR), and watchdog timer (3.3s typical timeout). It asserts an active-high push-pull RESET output during VCC brownout, MR assertion, or watchdog expiration, with guaranteed reset validity down to VCC = +1.1V. Used in battery-powered medical monitors and portable instrumentation requiring ultra-low quiescent current.

For engineers reviewing the MAX6865UK46D3S datasheet, MAX6865UK46D3S pinout, MAX6865UK46D3S application, or MAX6865UK46D3S equivalent, key selection criteria include its 4.625V reset threshold tolerance (±2.5%), 3.3s watchdog timeout, 170nA typical supply current at 2.5V, and compatibility with 1.2V–5.5V VCC operation across –40°C to +85°C.

Technical Context

The MAX6865UK46D3S implements a dual-trigger reset architecture: one path responds to VCC falling below 4.625V (±2.5%), another to MR low assertion, and a third to WDI inactivity exceeding 3.3s (typ). Its internal watchdog timer clears on any WDI edge, MR assertion, or RESET assertion - preventing false timeouts during system recovery.

Reset deassertion follows a fixed 150ms minimum timeout (D3 suffix) after VCC rises above threshold and MR deasserts. The active-high push-pull RESET output sources up to 500µA at VCC ≥ 2.38V while maintaining VOH ≥ 0.8×VCC, eliminating need for external pull-up components.

Key Specifications

Pinout & Package

MAX6865UK46D3S is housed in a RoHS-compliant 5-pin SOT23-5 package (2.9mm × 1.6mm × 1.1mm), optimized for space-constrained portable designs. 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), and 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 TPS3836K33DBVR and STM6315SDW13F, MAX6865UK46D3S delivers 14× lower supply current than the STM part and integrates watchdog supervision absent in the TI part - critical for safety-critical portable medical devices requiring both ultra-low power and firmware liveness assurance.

Availability

MAX6865UK46D3S is available at Aetrix Electronics and suitable for glucose monitors, patient vital sign loggers, handheld diagnostic scanners, and industrial wireless sensors requiring stable component supply across extended production lifecycles.

Supply support for MAX6865UK46D3S 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 MAX68xx family targets ultra-low-power microprocessor supervision in battery-critical systems, emphasizing nanopower operation, factory-trimmed accuracy, and integrated watchdog functionality without external components.

FAQ

What is the exact reset threshold voltage of MAX6865UK46D3S and how tightly is it specified?

The MAX6865UK46D3S has a factory-trimmed reset threshold of 4.625V with a guaranteed tolerance of ±2.5% over –40°C to +85°C. This corresponds to a range of 4.509V (min) to 4.741V (max), as defined in Table 2 of the datasheet. The threshold is referenced to the VCC pin and remains stable across temperature, with normalized VTH variation ≤ ±0.5% from –40°C to +85°C. This precision eliminates need for external calibration in 5V system monitoring.

Does MAX6865UK46D3S require an external pull-up resistor on its RESET pin?

No, MAX6865UK46D3S does not require an external pull-up resistor because it features an active-high push-pull RESET output. The internal driver sources current to pull RESET high when deasserted and sinks current to pull it low when asserted. This architecture directly interfaces with µP reset inputs rated for 1.2V–5.5V logic levels and removes dependency on board-level pull-up components - reducing BOM count and layout complexity.

How does the watchdog timer in MAX6865UK46D3S respond to WDI signal transitions?

The MAX6865UK46D3S watchdog timer clears on any rising or falling edge at the WDI pin - not just periodic toggling. A single edge resets the 3.3s timeout counter, making it robust against firmware timing jitter. If WDI remains static (high or low) beyond 3.3s (typ), the timer expires and asserts RESET for 150ms. The timer is also cleared during MR assertion or RESET assertion, ensuring coordinated fault recovery.

What is the minimum VCC voltage at which MAX6865UK46D3S guarantees valid RESET output behavior?

MAX6865UK46D3S guarantees valid RESET output behavior down to VCC = +1.1V, as explicitly stated in the Electrical Characteristics table. Below this voltage, RESET may become indeterminate. This specification ensures deterministic reset signaling during deep brownout events common in battery-powered systems nearing end-of-life, enabling safe shutdown or last-gasp data logging before power loss.

Can MAX6865UK46D3S be used in systems with VCC voltages below 1.8V, such as 1.2V logic rails?

Yes, MAX6865UK46D3S operates across VCC = 1.2V to 5.5V and guarantees RESET output performance down to 1.1V. At 1.2V VCC, the device draws only 190nA (typ) supply current and maintains VOH ≥ 0.8×VCC (≥0.96V) with 200µA source current - sufficient to drive modern 1.2V I/O standards. Its MR input accepts logic thresholds scaled to VCC (VIH ≥ 0.7×VCC), ensuring reliable manual reset activation even at lowest operating voltage.