Analog Devices Inc./Maxim Integrated MAX6868UK26D3S+T

Overview

MAX6868UK26D3S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, featuring active-high push-pull RESET output, manual reset (MR) input, and watchdog timer with 209s typical timeout. It monitors VCC down to +1.1V, asserts reset when supply drops below 2.625V (factory-trimmed threshold), and guarantees reset validity during brownout. Used in battery-powered medical devices like glucose monitors for reliable power-on initialization and software fault recovery.

For engineers reviewing the MAX6868UK26D3S+T datasheet, MAX6868UK26D3S+T pinout, MAX6868UK26D3S+T application, or MAX6868UK26D3S+T equivalent, key selection criteria include its 209s watchdog timeout, 2.625V reset threshold, 170nA typical supply current, and compatibility with low-voltage µP reset inputs requiring active-high assertion.

Technical Context

The MAX6868UK26D3S+T integrates voltage monitoring, manual reset control, and a watchdog timer that clears on any WDI edge and expires if WDI remains static beyond 209s (typ). Its reset logic asserts active-high RESET when VCC falls below 2.625V, MR is pulled low, or watchdog times out - holding output asserted for 150ms (min) after recovery.

It uses internal 10kΩ MR pullup and supports noise-immune operation down to VCC = +1.1V, with guaranteed VOL ≤ 0.3V at ISINK = 1.2mA and VOH ≥ 0.8×VCC at ISOURCE = 500µA. The device is immune to VCC transients ≤ 40µs at 100mV overdrive and requires no external components.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, surface-mount, lead-free (RoHS-compliant), footprint compatible with industry-standard 5-pin supervisory ICs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6864UK26D3S+T and TPS3838K26DBVR, MAX6868UK26D3S+T uniquely delivers active-high RESET, 209s watchdog, and nanopower operation in one 5-pin SOT23 - enabling simplified, long-life designs for medical and portable electronics where both reset polarity and firmware supervision are mandatory.

Availability

MAX6868UK26D3S+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, portable ECG recorders, and wireless sensor nodes requiring stable component supply across extended production lifecycles.

Supply support for MAX6868UK26D3S+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, mixed-signal, and power management ICs for industrial, medical, and communications applications.

The MAX6854–MAX6869 family delivers nanopower supervisory functions with integrated watchdog timers and factory-trimmed thresholds - engineered specifically for battery-critical portable medical and IoT endpoints demanding ultra-low ICC and robust fault coverage.

FAQ

What is the exact reset threshold voltage of the MAX6868UK26D3S+T?

The MAX6868UK26D3S+T has a factory-trimmed reset threshold voltage 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 device asserts active-high RESET when VCC falls below this threshold and holds it asserted for ≥150ms after VCC rises above it.

Does the MAX6868UK26D3S+T require an external pullup resistor on the RESET pin?

No, the MAX6868UK26D3S+T does not require an external pullup resistor because it features an active-high push-pull RESET output. The output actively drives high (≥0.8×VCC) when deasserted and low (≤0.3V) when asserted. This eliminates external components and ensures clean, fast transitions directly compatible with µP reset inputs expecting active-high assertion.

What is the watchdog timeout period for the MAX6868UK26D3S+T, and how is it cleared?

The MAX6868UK26D3S+T has a watchdog timeout period of 209s (typical), with min/max values of 95s/487s per Table 3. The watchdog timer is cleared by any rising or falling edge on the WDI pin - including brief pulses ≥150ns - and also resets automatically when MR is asserted or RESET is active. This edge-sensitive clearing prevents false timeouts during normal firmware operation.

Can the MAX6868UK26D3S+T operate reliably at VCC = 1.2V?

Yes, the MAX6868UK26D3S+T is fully specified to operate at VCC = 1.2V (minimum), with guaranteed reset assertion down to VCC = +1.1V. At 1.2V, supply current remains ultra-low (≤370nA typ), RESET output low voltage is ≤0.3V at 50µA sink, and watchdog timing remains functional. This makes it suitable for single-cell LiFePO₄ or alkaline systems with deep discharge profiles.

How does the MR (manual reset) input function on the MAX6868UK26D3S+T?

The MR input on the MAX6868UK26D3S+T is active-low with an internal 10kΩ pullup to VCC. Driving MR low for ≥1µs initiates a full reset cycle: RESET goes high immediately and remains high for ≥150ms after MR returns high. MR accepts CMOS logic levels and can be driven by open-drain outputs or a momentary switch to GND; no external debounce is required due to built-in 200ns glitch rejection.