Analog Devices Inc./Maxim Integrated MAX6865UK40D4L+T

Overview

MAX6865UK40D4L+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, providing voltage monitoring (4.000V reset threshold), manual reset input (MR), and watchdog timer (209s typical timeout). It asserts an active-high push-pull RESET output during VCC brownout, MR assertion, or watchdog timeout, with guaranteed reset validity down to VCC = +1.1V. Used in battery-powered medical devices like glucose monitors for reliable power-up sequencing and firmware crash recovery.

For engineers reviewing the MAX6865UK40D4L+T datasheet, MAX6865UK40D4L+T pinout, MAX6865UK40D4L+T application, or MAX6865UK40D4L+T equivalent, key selection criteria include its 4.000V factory-trimmed threshold, 1200ms minimum reset timeout (D4), 209s watchdog period (L suffix), ultra-low 170nA supply current, and compatibility with noisy low-voltage systems requiring robust transient immunity.

Technical Context

The MAX6865UK40D4L+T integrates a precision bandgap-based voltage monitor, a digital watchdog timer with edge-triggered clearing logic, and an internal 10kΩ MR pullup. Its reset assertion path combines analog threshold detection with a digital timeout counter that holds RESET asserted for ≥1200ms after VCC recovery or MR release.

Watchdog operation relies on WDI edge detection (min pulse width 150ns); the timer resets on any rising or falling edge and expires only if WDI remains static beyond 209s (typ). The active-high push-pull RESET output is referenced to VCC and sinks ≤0.3V at 1.2mA load, ensuring clean interface with µP reset inputs.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, -40°C to +85°C operating range.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK40D4L+T, the MAX6865UK40D4L+T's active-high RESET simplifies interface with modern low-voltage µPs; versus TPS3838K33DBVR, it delivers 10× lower supply current and essential watchdog protection for safety-critical firmware.

Availability

MAX6865UK40D4L+T is available at Aetrix Electronics and suitable for portable medical devices, industrial handheld scanners, smart energy meters, and battery-powered IoT endpoints requiring stable component supply across extended product lifecycles.

Supply support for MAX6865UK40D4L+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 in industrial, medical, and communications markets.

The MAX6854–MAX6869 family delivers nanopower supervisory functions for battery-constrained systems, emphasizing ultra-low ICC, guaranteed low-VCC operation, and integrated watchdog timers to enhance firmware reliability.

FAQ

What is the exact reset threshold voltage of the MAX6865UK40D4L+T?

The MAX6865UK40D4L+T features a factory-trimmed reset threshold of 4.000V with ±2.5% tolerance over temperature. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "40" corresponds to 4.000V nominal. The device guarantees valid reset assertion down to VCC = +1.1V, making it suitable for monitoring 3.3V and 5V rails in brownout conditions. The MAX6865UK40D4L+T does not require external resistor networks to set this threshold.

Does the MAX6865UK40D4L+T support both manual reset and watchdog functionality?

Yes, the MAX6865UK40D4L+T integrates both manual reset (MR) and watchdog timer (WDI) functions. The MR pin is active-low with internal 10kΩ pullup, allowing direct switch-to-GND implementation. The WDI pin monitors µP activity and triggers reset if no edge occurs within 209s (L-suffix). Both functions independently assert the same active-high push-pull RESET output, which remains asserted for ≥1200ms after recovery. This dual-fault coverage is explicitly documented in the Selector Guide and Pin Description sections for MAX6865.

What is the meaning of the 'D4' and 'L' suffixes in MAX6865UK40D4L+T?

In MAX6865UK40D4L+T, 'D4' specifies the reset timeout period as 1200ms (minimum), per Table 4 of the datasheet. 'L' denotes the watchdog timeout option of 209s (typical), defined in Table 3. These suffixes are part of Maxim's standardized ordering code: 'UK40' sets the 4.000V threshold, 'D4' selects the longest standard reset delay, and 'L' chooses the long watchdog interval-distinct from 'S' (3.3s). The '+T' indicates lead-free packaging. All three elements are required for correct device identification and function.

Can the MAX6865UK40D4L+T operate reliably at VCC = 1.2V?

Yes, the MAX6865UK40D4L+T operates over VCC = 1.2V to 5.5V and guarantees RESET validity down to VCC = +1.1V, as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. At 1.2V, supply current is 190nA (typ), and RESET output maintains VOH ≥ 0.8 × VCC under 200µA source load. This low-voltage capability enables use in partially discharged Li-ion or alkaline battery systems where other supervisors fail. The MAX6865UK40D4L+T's performance at 1.2V is validated across -40°C to +85°C.

Is the MAX6865UK40D4L+T pin-compatible with other devices in the MAX68xx family?

The MAX6865UK40D4L+T uses the standard 5-pin SOT23-5 package with identical pinout to MAX6864/MAX6866 (RESET/MR/WDI/GND/VCC), but differs from MAX6861–MAX6863 (which use CT instead of WDI) and MAX6854–MAX6856 (which lack WDI). Pin compatibility is confirmed in the Pin Configurations diagram and Selector Guide. However, RESET polarity differs: MAX6865 provides active-high push-pull, while MAX6864 offers active-low. Direct substitution requires verification of µP reset input polarity and absence of CT pin dependencies.