Analog Devices Inc./Maxim Integrated MAX6864UK18D3S+

Overview

The MAX6864UK18D3S+ from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, integrating voltage monitoring (1.8V reset threshold), manual reset input (MR), and watchdog timer (3.3s timeout). It asserts an active-low push-pull RESET output during VCC brownout, MR assertion, or watchdog timeout, with guaranteed reset validity down to VCC = +1.1V. It targets ultra-low-power portable medical and consumer devices requiring reliable power-on reset and firmware crash recovery.

For engineers reviewing the MAX6864UK18D3S+ datasheet, MAX6864UK18D3S+ pinout, MAX6864UK18D3S+ application, or MAX6864UK18D3S+ equivalent, key selection criteria include its 170nA typical supply current, factory-trimmed 1.8V reset threshold, 300ms minimum reset timeout, 3.3s watchdog period, and SOT23-5 footprint compatibility with TPS383x-series supervisors.

Technical Context

The MAX6864UK18D3S+ implements a dual-monitoring architecture: a precision bandgap-based voltage detector for VCC supervision and an edge-triggered watchdog timer that clears on any WDI transition (rising or falling) and expires if WDI remains static beyond 3.3s (typ). Its internal 10kΩ MR pullup enables direct switch interfacing without external components.

Reset assertion is synchronized across all fault sources-VCC drop below 1.8V, MR low, or WDI timeout-with a fixed 300ms (min) deassertion delay after fault clearance. The push-pull RESET output drives low to ≤0.3V at 1.2mA sink (VCC ≥ 2.38V) and high to ≥0.8×VCC at 500µA source, ensuring robust logic-level compatibility with µP reset inputs.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5 (lead-free, RoHS-compliant), 2.9mm × 1.6mm footprint, 1.1mm height.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3836K33DBVR and MAX6369KA29D3+, the MAX6864UK18D3S+ uniquely combines 1.8V precision reset, MR, and watchdog in a pin-compatible SOT23-5 package-enabling drop-in upgrade of legacy supervisors while adding firmware resilience without layout change.

Availability

MAX6864UK18D3S+ is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, MP3 players, and smart pagers requiring stable component supply and long-term lifecycle support.

Supply support for MAX6864UK18D3S+ 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 in industrial, medical, and consumer markets.

The MAX6864UK18D3S+ belongs to the nanopower µP supervisory family engineered for ultra-low-current battery-powered systems where reset reliability and watchdog-assisted firmware recovery are critical.

FAQ

What is the exact reset threshold voltage of the MAX6864UK18D3S+?

The MAX6864UK18D3S+ has a factory-trimmed reset threshold of 1.800V with ±2.5% tolerance over -40°C to +85°C. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "18" corresponds to 1.800V nominal. The device guarantees valid reset assertion down to VCC = +1.1V, making it suitable for deep-brownout scenarios in battery-powered MAX6864UK18D3S+ applications.

Does the MAX6864UK18D3S+ require external components for basic operation?

No, the MAX6864UK18D3S+ operates autonomously with no external components required. Its MR input features an internal 10kΩ pullup to VCC, the RESET output is push-pull active-low, and the watchdog timer uses an on-chip oscillator. Only a 0.1µF ceramic capacitor from VCC to GND is recommended for noise immunity - a standard practice for all MAX6864UK18D3S+ deployments in portable equipment.

What is the watchdog timeout period for the MAX6864UK18D3S+ and how is it triggered?

The MAX6864UK18D3S+ features a 3.3s typical watchdog timeout period (suffix "S"), as specified in Table 3. It triggers when the WDI input remains static (high or low) longer than this period. The internal timer clears on every rising or falling edge at WDI - including pulses as short as 150ns - ensuring reliable detection of firmware activity in the MAX6864UK18D3S+.

Can the MAX6864UK18D3S+ be used with a 1.2V supply rail?

Yes, the MAX6864UK18D3S+ operates across VCC = 1.2V to 5.5V and guarantees reset validity down to VCC = +1.1V. However, its 1.8V reset threshold means it will assert reset when a 1.2V rail is applied - making it unsuitable for supervising 1.2V rails directly. It is intended for 1.8V+ rails; for 1.2V supervision, a different threshold variant like MAX6864UK12D3S+ would be required. This behavior is inherent to the MAX6864UK18D3S+ design.

Is the MAX6864UK18D3S+ pin-compatible with Texas Instruments TPS3836 series?

Yes, the MAX6864UK18D3S+ is pin-compatible with the TPS3836/TPS3837/TPS3838 family per the datasheet's Feature section. Pin 1 is RESET, Pin 2 is GND, Pin 3 is MR, Pin 4 is WDI, and Pin 5 is VCC - matching the TPS3836 pinout exactly. This allows direct replacement in existing layouts, though designers must verify that the added WDI function and 3.3s watchdog align with system firmware requirements for the MAX6864UK18D3S+.