Analog Devices Inc./Maxim Integrated MAX6866UK26D3L

Overview

MAX6866UK26D3L from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 2.625V reset threshold (suffix D3 = 150ms min timeout), and integrated watchdog timer with 209s typical timeout (suffix L). It monitors VCC, responds to manual reset (MR), and asserts active-low open-drain RESET during brownout, power-up, or watchdog expiration - used in battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6866UK26D3L datasheet, MAX6866UK26D3L pinout, MAX6866UK26D3L application, or MAX6866UK26D3L equivalent, key selection criteria include its 2.625V threshold accuracy over temperature, guaranteed RESET validity down to VCC = +1.1V, immunity to sub-40µs VCC transients, and compatibility with 1.2V–5.5V supply rails in space-constrained portable systems.

Technical Context

The MAX6866UK26D3L integrates three core functions: precision voltage monitoring with ±2.5% threshold tolerance, a manual reset input (MR) with 250ns delay and internal 10kΩ pullup, and a watchdog timer that triggers reset if WDI remains static beyond 209s (typ). Its reset assertion logic combines VCC undervoltage, MR low, and WDI timeout conditions using internal comparators and a monostable timeout generator.

It employs BiCMOS process technology for ultra-low ICC (170nA typ at 2.5V) while maintaining robust noise immunity - including 200ns MR glitch rejection and transient immunity validated down to 100mV overdrive. The open-drain RESET output requires external pullup and supports level-shifting across 0–5.5V logic domains.

Key Specifications

Pinout & Package

MAX6866UK26D3L uses a 5-pin SOT23-5 package (3.0mm × 1.7mm × 1.3mm height), lead-free, rated for -40°C to +85°C operation. Pin 1 is RESET (active-low open-drain), Pin 2 is GND, Pin 3 is MR (active-low manual reset), Pin 4 is WDI (watchdog input), and Pin 5 is VCC (supply input).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK26D3L, MAX6866UK26D3L offers identical core supervision but adds WDI capability; versus TPS3836K33DBVR, it delivers 10× lower ICC and integrated watchdog - making it superior for long-life, autonomous portable medical devices.

Availability

MAX6866UK26D3L is available at Aetrix Electronics and suitable for glucose monitors, portable ECG recorders, wireless patient tags, and low-power wearable trackers requiring stable component supply across industrial and medical OEM programs.

Supply support for MAX6866UK26D3L 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, sensing, and interface applications in industrial, medical, and communications markets.

The MAX6854–MAX6869 family was engineered specifically for ultra-low-power microprocessor supervision in battery-constrained portable medical and handheld electronics, emphasizing nanoscale ICC, wide VCC range, and integrated watchdog reliability.

FAQ

What is the exact reset threshold voltage of MAX6866UK26D3L?

The MAX6866UK26D3L has a factory-trimmed reset threshold of 2.625V, 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 '26' corresponds to 2.625V nominal. The threshold remains stable across temperature, with normalized variation <±0.5% from -40°C to +85°C per Figure toc06.

Does MAX6866UK26D3L support active-high reset output?

No, MAX6866UK26D3L provides only active-low open-drain RESET output (Pin 1). Unlike variants such as MAX6865UK26D3L (active-high push-pull) or MAX6863UK26 (open-drain active-low with CT), the MAX6866UK26D3L's reset output is strictly active-low and requires an external pullup resistor. This is specified in the MAX6864/MAX6865/MAX6866 Pin Description section and functional diagram.

What is the watchdog timeout behavior of MAX6866UK26D3L?

MAX6866UK26D3L features a watchdog timer with 209s typical timeout (L-suffix), with min/max of 95s/487s over temperature. The timer resets on any WDI edge (rising or falling) and triggers RESET if WDI remains static beyond timeout. While RESET is asserted, the watchdog stops counting; it resumes immediately upon RESET deassertion, as detailed in Figure 3 and Table 3.

Can MAX6866UK26D3L operate below 1.2V supply?

MAX6866UK26D3L is specified for VCC = 1.2V to 5.5V, but its RESET output is guaranteed valid down to VCC = +1.1V per Electrical Characteristics table. Below 1.2V, supply current increases and timing parameters degrade; operation below 1.1V is not characterized and may result in undefined RESET state. The 1.1V guarantee ensures reliable reset assertion during deep brownout.

How does the MR input function on MAX6866UK26D3L?

The MR input on MAX6866UK26D3L is active-low with internal 10kΩ pullup to VCC. Driving MR low asserts RESET for the full timeout period (150ms min), even if MR returns high earlier. MR accepts CMOS logic levels, rejects <200ns glitches, and requires ≥1µs pulse width. If unused, MR may be left floating or tied to VCC - no external components are needed.