Analog Devices Inc./Maxim Integrated MAX6865UK21D1L+T

Overview

The MAX6865UK21D1L+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, a factory-trimmed 2.100V reset threshold (±2.5%), 10ms minimum reset timeout, and integrated watchdog timer with 209s typical timeout. It monitors VCC, responds to manual reset (MR), and asserts active-high push-pull RESET during brownout, power-up, or watchdog expiration - used in battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK21D1L+T datasheet, MAX6865UK21D1L+T pinout, MAX6865UK21D1L+T application, or MAX6865UK21D1L+T equivalent, key selection criteria include guaranteed RESET validity down to VCC = +1.1V, immunity to short VCC transients (<40µs at 100mV overdrive), pin-selectable reset delay capability (not applicable to this variant), and compatibility with 1.2V–5.5V supply rails.

Technical Context

This device implements a precision bandgap-based voltage monitor with 2.5% threshold tolerance and 0.5% hysteresis, combined with a digital watchdog timer that clears on any WDI edge and expires if WDI remains static beyond 209s (typ). The internal reset timeout generator uses a temperature-stable RC oscillator calibrated for ±20% variation across –40°C to +85°C.

The MAX6865UK21D1L+T integrates MR input with 10kΩ internal pullup, glitch rejection of 200ns, and 250ns MR-to-RESET delay. Its push-pull active-high RESET output delivers VOH ≥ 0.8×VCC at 500µA source current and VOL ≤ 0.3V at 1.2mA sink current - ensuring robust interface with 1.8V/2.5V/3.3V µPs without external level-shifting.

Key Specifications

Pinout & Package

Package: 5-pin SOT23 (lead-free, +T suffix), 2.9mm × 1.6mm footprint, 1.1mm height, thermal pad not present.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6865UK21D1L+T, the MAX6864UK21D1L+T offers identical supervision timing but inverted reset polarity - requiring µP reset pin compatibility verification; the TPS3838K21DBVR provides higher threshold accuracy but sacrifices watchdog capability and draws nearly double the quiescent current.

Availability

MAX6865UK21D1L+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered instrumentation, and low-power embedded controllers requiring stable component supply with full lifecycle support.

Supply support for MAX6865UK21D1L+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, sensing, and connectivity applications in industrial, medical, and consumer systems.

The MAX68xx family targets ultra-low-power microprocessor supervision in space- and energy-constrained devices, emphasizing nanopower operation, small footprint, and robust reset timing under dynamic supply conditions.

FAQ

What is the exact reset threshold voltage of the MAX6865UK21D1L+T?

The MAX6865UK21D1L+T has a factory-trimmed reset threshold of 2.100V 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 "21" corresponds to 2.100V nominal. The device guarantees valid RESET assertion down to VCC = +1.1V, supporting reliable operation near the threshold boundary.

Does the MAX6865UK21D1L+T include a watchdog timer, and what is its timeout?

Yes, the MAX6865UK21D1L+T includes a watchdog timer with "L"-suffix configuration, providing a typical timeout of 209 seconds (min 95s, max 487s). The timer clears on any rising or falling edge at the WDI pin and expires only if WDI remains static beyond the timeout period - enabling supervision of long-duration firmware tasks without spurious resets.

What is the function of Pin 1 on the MAX6865UK21D1L+T, and how does it differ from other MAX68xx variants?

Pin 1 of the MAX6865UK21D1L+T is the active-high push-pull RESET output. Unlike MAX6864/MAX6866 (active-low RESET) or MAX6867/MAX6869 (open-drain), this variant drives high during reset assertion and requires no external pullup. Its VOH ≥ 0.8×VCC at 500µA ensures compatibility with 1.8V–3.3V µP reset inputs without level-shifting circuitry.

Can the MAX6865UK21D1L+T operate from a 1.5V supply?

Yes, the MAX6865UK21D1L+T operates from VCC = 1.2V to 5.5V and guarantees RESET validity down to VCC = +1.1V. At 1.5V, it delivers 170nA typical supply current and maintains full functionality - including MR input detection, WDI edge sensing, and RESET assertion - making it suitable for single-cell alkaline or NiMH systems.

Is the MAX6865UK21D1L+T pin-compatible with the TPS3836 series?

No, the MAX6865UK21D1L+T is not pin-compatible with the TPS3836 series. While both are 5-pin SOT23 supervisors, the TPS3836 places RESET on Pin 1 (active-low open-drain) and GND on Pin 2, whereas MAX6865UK21D1L+T assigns RESET to Pin 1 (active-high push-pull) and GND to Pin 2 - same pin numbering but incompatible electrical behavior and function mapping.