Analog Devices Inc./Maxim Integrated MAX6865UK28D1S+T

Overview

The MAX6865UK28D1S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, factory-trimmed 2.800V reset threshold (suffix D1S), 10ms minimum reset timeout, and integrated watchdog timer with 3.3s typical timeout. It monitors VCC, responds to manual reset (MR) assertion, and triggers reset on watchdog expiration - designed for battery-critical systems like glucose monitors and portable medical devices.

For engineers reviewing the MAX6865UK28D1S+T datasheet, MAX6865UK28D1S+T pinout, MAX6865UK28D1S+T application, or MAX6865UK28D1S+T equivalent, key selection criteria include its guaranteed reset validity down to VCC = +1.1V, immunity to short VCC transients (<40µs at 100mV overdrive), push-pull active-high RESET output, and compatibility with noisy low-voltage embedded environments requiring deterministic power-on reset behavior.

Technical Context

This device integrates three core functions: precision voltage monitoring with ±2.5% threshold accuracy across -40°C to +85°C, a manual reset input with 250ns MR-to-reset delay and internal 10kΩ pullup, and a watchdog timer that clears on any WDI edge and expires after 3.3s (typ) if inactive. The reset output remains asserted for ≥10ms after VCC exceeds threshold and MR deasserts.

Its BiCMOS process enables stable operation from 1.2V to 5.5V supply, with supply current rising only to 400nA at 5.0V and maintaining <370nA at 1.8V. The push-pull active-high RESET output delivers VOH ≥0.8×VCC at ISOURCE = 500µA and VOL ≤0.3V at ISINK = 1.2mA, ensuring robust interfacing with modern low-voltage µPs.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount. Compact 2.9mm × 1.6mm footprint with 0.95mm height, optimized for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK28D1S+T and TPS3836K28DBVR, the MAX6865UK28D1S+T uniquely combines ultra-low 170nA current, 2.8V precision threshold, 10ms fast reset release, and integrated 3.3s watchdog - making it optimal for compact, battery-sensitive medical and portable electronics demanding both power efficiency and software fault resilience.

Availability

MAX6865UK28D1S+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, MP3 players, and cell phone baseband modules requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.

Supply support for MAX6865UK28D1S+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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, medical, and consumer applications.

The MAX68xx family was designed specifically for ultra-low-power microprocessor supervision in battery-operated medical and portable equipment, emphasizing nanoscale current consumption, precise voltage thresholds, and integrated watchdog safety.

FAQ

What is the exact reset threshold voltage of the MAX6865UK28D1S+T?

The MAX6865UK28D1S+T has a factory-trimmed reset threshold of 2.800V, with guaranteed tolerance of ±2.5% over the full -40°C to +85°C operating temperature range. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "28" corresponds to 2.800V nominal. The MAX6865UK28D1S+T uses this precise threshold to initiate reset when the monitored VCC rail falls below 2.8V, ensuring reliable brownout protection for 2.8V-systems.

Does the MAX6865UK28D1S+T support active-high or active-low reset output?

The MAX6865UK28D1S+T features a push-pull active-high RESET output - meaning the RESET pin drives high during reset assertion and low when deasserted. This is confirmed in the MAX6865 pin description (page 8) and Selector Guide (page 16), where MAX6865 is marked with "√" under "Push-Pull Active High". Unlike open-drain variants, this configuration requires no external pullup resistor and simplifies interface with µPs expecting active-high reset signals.

What is the watchdog timeout period for the MAX6865UK28D1S+T?

The MAX6865UK28D1S+T has a watchdog timeout period of 3.3s (typical), specified by the "S" suffix in its part number. As documented in Table 3 (Watchdog Timeout) and Ordering Information, "S" denotes the short watchdog option (min 1.5s, typ 3.3s, max 7.75s). The internal watchdog timer clears on any rising or falling edge at the WDI pin and expires only if WDI remains static beyond this interval - providing deterministic software fault detection without requiring precise timing margins.

Can the MAX6865UK28D1S+T operate reliably at VCC = 1.5V?

Yes, the MAX6865UK28D1S+T operates reliably down to VCC = 1.2V (minimum specified), and its reset function remains valid even as low as VCC = 1.1V. Per Electrical Characteristics (page 2), the device guarantees functional operation and correct reset assertion across VCC = 1.2V to 5.5V, with supply current at 170nA (typ) at 2.5V and rising only to 370nA at 1.8V. At 1.5V, the MAX6865UK28D1S+T maintains full functionality including MR response, WDI edge detection, and RESET output drive strength.

Is the MAX6865UK28D1S+T pin-compatible with other MAX68xx supervisory circuits?

The MAX6865UK28D1S+T shares the same 5-pin SOT23-5 package and pinout as all MAX6864–MAX6869 variants (pin 1 = RESET, pin 2 = GND, pin 3 = MR, pin 4 = WDI, pin 5 = VCC), as shown in the Pin Configurations diagram (page 15). However, it is not pin-compatible with MAX6854–MAX6863 families, which assign different functions to pin 4 (e.g., CT or I.C.). Therefore, direct substitution is only valid within the MAX6864–MAX6869 series - the MAX6865UK28D1S+T can replace MAX6864UK28D1S+T or MAX6866UK28D1S+T without layout change, but not MAX6861 or MAX6855.